annotate doc/v2_planning/dataset.txt @ 1429:b0141efbf6a2

fix loading of sparse utlc dataset when PYLEARN_DATA_ROOT have more then 1 directory.
author Frederic Bastien <nouiz@nouiz.org>
date Tue, 08 Feb 2011 16:17:56 -0500
parents 04b988fb00b6
children
rev   line source
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Yoshua Bengio <bengioy@iro.umontreal.ca>
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1 Discussion of Function Specification for Dataset Types
f82093bf4405 adding learner.txt and dataset.txt in v2_planning/
Yoshua Bengio <bengioy@iro.umontreal.ca>
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2 ======================================================
f82093bf4405 adding learner.txt and dataset.txt in v2_planning/
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3
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Dumitru Erhan <dumitru.erhan@gmail.com>
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4 Some talking points from the September 2 meeting:
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5
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6 * Datasets as views/tasks (Pascal Vincent's idea): our dataset specification
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Frederic Bastien <nouiz@nouiz.org>
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7 needs to be flexible enough to accommodate different (sub)tasks and views of
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Frederic Bastien <nouiz@nouiz.org>
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8 the same underlying data.
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Dumitru Erhan <dumitru.erhan@gmail.com>
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9 * Datasets as probability distributions from which one can sample.
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Olivier Delalleau <delallea@iro>
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10 * That's not something I would consider to be a dataset-related problem to
fb6cae14fd07 dataset: Comment about viewing a dataset as a distribution
Olivier Delalleau <delallea@iro>
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11 tackle now: a probability distribution in Pylearn would probably be a
fb6cae14fd07 dataset: Comment about viewing a dataset as a distribution
Olivier Delalleau <delallea@iro>
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12 different kind of beast, and it should be easy enough to have a
fb6cae14fd07 dataset: Comment about viewing a dataset as a distribution
Olivier Delalleau <delallea@iro>
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13 DatasetToDistribution class for instance, that would take care of viewing a
fb6cae14fd07 dataset: Comment about viewing a dataset as a distribution
Olivier Delalleau <delallea@iro>
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14 dataset as a probability distribution. -- OD
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15 * Our specification should allow transparent handling of infinite datasets (or
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16 simply datasets which cannot fit in memory)
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17 * GPU/buffering issues.
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18
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19 Commiteee: DE, OB, OD, AB, PV
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20 Leader: DE
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21
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22 Some ideas from existing ML libraries:
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23
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24 - PyML: notion of dataset containers: VectorDataSet, SparseDataSet, KernelData,
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25 PairDataSet, Aggregate. Ultimately, the learner decides
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26 - mlpy: very primitive notions of data (simple 2D matrices)
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27 - PyBrain: Datasets are geared towards specific tasks: ClassificationDataSet,
20a1af112a75 dataset: Looked into datasets from some other ML libraries
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28 SequentialDataSet, ReinforcementDataSet, ... Each class is quite
20a1af112a75 dataset: Looked into datasets from some other ML libraries
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29 constrained and may have a different interface.
20a1af112a75 dataset: Looked into datasets from some other ML libraries
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30 - MDP: Seems to have restrictions on the type of data being passed around, as
20a1af112a75 dataset: Looked into datasets from some other ML libraries
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31 well as its dimensionality ("Input array data is typically assumed to be
20a1af112a75 dataset: Looked into datasets from some other ML libraries
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32 two-dimensional and ordered such that observations of the same variable are
20a1af112a75 dataset: Looked into datasets from some other ML libraries
Olivier Delalleau <delallea@iro>
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33 stored on rows and different variables are stored on columns.")
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34 - Orange: Data matrices, with names and types associated to each column.
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35 Basically there seems to be only one base dataset class that contains the
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36 data. Data points are lists (of values corresponding to each column).
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37 - APGL: Hard to say how they deal with data from the documentation alone.
5c14d2ffcbb3 dataset: Looked into a few more existing ML libraries
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38 - Monte: Data is simply numpy arrays.
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39 - scikits.learn: Dataset is a simple container with e.g. dataset.data being
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40 a 2D numpy array of input features, and dataset.target the target vector.
5c14d2ffcbb3 dataset: Looked into a few more existing ML libraries
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41 - Shogun: Vade Retro C++! (may be worth looking into their feature concept
5c14d2ffcbb3 dataset: Looked into a few more existing ML libraries
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42 though).
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43 - Any more worth looking at?
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44
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45 A few things that our dataset containers should support at a minimum:
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46
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47 - streams, possibly infinite
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48 - task/views of the data for different problems
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49 - indexing & slicing
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50 - pairs or triples or etc of examples
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51 - a 'distance/gram matrix' container (imagine that the data is given to you
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52 as a distance matrix)
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53 - multi-dimensional time-series (again, maybe with pairs/triples, maybe
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54 given to you as a distance matrix over time)
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55
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56 Another question to consider is the following: how tight should it integrate
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57 with Theano? Do we want to be able to store data as shared variables or just
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58 have an option for that? Theano + GPU constrains things that we can do (in terms
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59 of sizes, buffering, etc): these are things we need to think about, but it's not
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60 clear whether we should aim for building them into the interface.
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61
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62 Task views of the data for different problems: How can we achieve this? Should
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63 we simply have a set of standard dataset descriptors ('classification',
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64 'regression', 'multi-label', 'density_estimation') and have a set_view method
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65 that changes the current dataset view type?
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66
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67 There is then the question of how to approach the design of a Dataset class from
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Dumitru Erhan <dumitru.erhan@gmail.com>
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68 an OOP perspective. So far, my (Dumi's) idea is to have an almost 'abstract class'
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69 Dataset that doesn't implement any methods except a few setters/getters. The reason
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70 to have the methods listed that way is to have a common 'specification', but classes
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71 that inherit from Dataset need not implement every single method (only the ones
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72 that are relevant) and can obviously implement other methods as appropriate. The
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73 reason to have a common specification (as abstract as it might be) is to, well,
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74 have a common specification that would make our code clearer and cleaner.
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75
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76 An example of what I (Dumi) am thinking in terms of concrete API:
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77
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78 class Dataset:
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79 def __init__(self):
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80 self.type = None
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81 self.in_memory = None
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82 self.inputs = None # list of filepaths, or objects in memory, or...
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83 self.outputs = None
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84
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85 def get_example(self,example_index):
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86 raise NotImplementedError()
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87
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88 def get_next_example(self):
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89 raise NotImplementedError()
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90
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91 def get_batch(self,batch_index):
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92 raise NotImplementedError()
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93
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94 def get_next_batch(self):
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95 raise NotImplementedError()
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96
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97 def get_slice(self,slice_object):
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98 raise NotImplementedError()
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99
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100 def set_view(self,view_type):
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101 self.view_type = view_type
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102 self.n_classes = None
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103
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104 def set_n_classes(self,n_classes):
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105 self.n_classes = n_classes
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106
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107 def set_batch_size(self,batch_size):
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108 self.batch_size = batch_size
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109
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110 You will note that there is no notion of train/valid/test in this class: I think we should
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111 just have a train dataset, a valid one and a test one instead or (if it's in one
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112 big file or infinite stream) just handle the split ourselves (via slicing, for
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113 instance). I (Dumi) am of the opinion that it keeps things cleaner, but the
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114 specification does not preclude more fine-grained 'splitting' of the data.
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115
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116 A concrete implementation would look like this (we would have one class per
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117 dataset that we use, and the class declaration contains essentially everything
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118 there is to know about the dataset):
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119
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120 .. code-block:: python
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121
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122 class MNIST(Dataset):
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123 def __init__(self,inputs=['train_x.npy'],outputs=['train_y.npy']):
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124 self.type='standard_xy'
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125 self.in_memory = True
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126 self.inputs = inputs # load them or create
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127 self.outputs = outputs
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128 self.set_view('classification')
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129 self.set_n_classes(10)
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130 self.set_batch_size(20)
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131 self.n_batches = self._compute_n_batches()
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132
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133 def get_batch(self,batch_index):
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134 x,y = self._fetch_batch(batch_index)
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135 if self.view_type == 'classification':
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136 return x,numpy.int32(y)
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137 elif self.view_type == 'density_estimation':
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138 return x
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139 else:
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140 raise NotImplementedError()
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141
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142 def shared_data(self):
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143 shared_x = theano.shared(numpy.asarray(self.inputs, dtype=theano.config.floatX))
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144 shared_y = theano.shared(numpy.asarray(self.outputs, dtype=theano.config.floatX))
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145 return shared_x, T.cast(shared_y, 'int32')
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146
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147 def _compute_n_batches(self):
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148 pass
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149
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150 def _fetch_batch(self,batch_index):
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151 pass
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152
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153 But nothing stops you from defining get_train_batch, get_valid_batch and stuff
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154 like that!
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155
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156 So we'd use it as:
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157
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158 train_mnist = MNIST(inputs = ['train_x.npy'], outputs = ['train_y.npy'])
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159 valid_mnist = MNIST(inputs = ['valid_x.npy'], outputs = ['valid_y.npy'])
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160
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161 x,y = train_mnist.get_batch(0)
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162 train_mnist.set_view('density_estimation')
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163 x = train_mnist.get_batch(0)
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164
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165 or
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166
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167 mnist_data = MNIST(inputs = ['x.npy'], outputs = ['y.npy'])
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168 batches_train = range(int(mnist_data.n_batches*0.8))
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169 batches_valid = range(int(mnist_data.n_batches*0.8),mnist_data.n_batches)
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170
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171 xt,yt = mnist_data.get_batch(batches_train[0])
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172 xv,yv = mnist_data.get_batch(batches_valid[0])
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173
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174
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175
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176
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177 COMMENTS
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178 ~~~~~~~~
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179
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180 JB asks: How about asking datasets to also provide a visualization mechanism
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181 for showing / playing individual examples from the dataset, but also other
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182 external objects that are similar to dataset examples (e.g. filters from a
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183 weight matrix that filters images). This doesn't have to be complicated, and it
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184 can be shared between datasets that exist in one modality (e.g. image datasets
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185 can all use an image-rending method)
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186
1131
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187 OD replies: Besides being able to display data without prior knowledge of the
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188 kind of data inside a dataset, is there any reason to put this within the
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189 dataset class? If not, it seems to me it may be more appropriate to have a way
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190 for the dataset to describe the kind of data it holds, and keep the
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191 visualization code separate from the dataset itself. It would make it easier
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192 in particular to try different visualization systems, and description of the
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193 data may turn out to be useful for other reasons (however, it also means we'd
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194 need to come up with a good way to describe data, which could prove
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195 difficult).
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196
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197 JB asks: What may be passed as argument to the functions in Dataset, and what
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198 can be expected in return? Are there side effects (e.g. on the state of the
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199 Dataset) associated with any of the functions?
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200
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201 JB asks: What properties are part of the Dataset API? What possible types can
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202 they have, are they expected to be read-only or writeable? What do they mean?
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203
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204
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205 JB asks: What is a view? Does set_view change the Dataset or return a new
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206 Dataset with a certain view of the original (in which case call it get_view)?
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207 Does the view imply the types of the return-value of functions like
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208 get_batch? What is the difference between the view and the subclasses of
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209 Dataset in PyML?
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210
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211 JB asks: Do container formats (I'm thinking of HDF5) offer features for fast
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212 retrieval that we would like to expose via this interface?
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213
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214 JB asks: How would you recommend using this sort of dataset in a boosting
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215 algorithm where points need to be re-weighted.
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216
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217
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218 JB asks: Do we want to provide for the possibility of feedback that modifies the
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219 dataset? For example, curriculum learning might be adaptive in this sense, or
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220 if we wanted to provide a virtual world for an agent as a dataset then we need
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221 to provide 'actions' to get the next batch. Could this be done in the current
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222 API?
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223
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224
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225 Field names and attributes
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226 ~~~~~~~~~~~~~~~~~~~~~~~~~~
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227
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228 OD: One important question is how to handle fields' names and characteristics.
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229 For instance, it can be useful to know that the 3rd input field represents a
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230 number of fingers, and is a non-negative discrete field whose numeric value is
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231 meaningful (compared, to, say, an integer index that would correspond to an
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232 animal's category). We mentioned metadata during the meeting, but we did not
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233 get into its details: that may be a place where to put this kind of things.
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234
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235
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236 Freeing memory
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237 ~~~~~~~~~~~~~~
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238
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239 OD: It is sometimes useful to be able to free memory used by previous
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240 computations. A typical example is when you load in memory the original
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241 dataset, then perform various processing steps, ending with a new dataset that
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242 you also store in memory before feeding it to the learner. Unless you very
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243 carefully design your code to avoid it, your original dataset will still
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244 remain in memory (as well as maybe the results of some computations performed
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245 along the way). So there may be a use for a `clear()` method that would be
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246 called by the topmost dataset (the one doing the final memory caching), and
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247 would be forwarded iteratively to previous datasets so as to get back all this
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248 wasted memory space.
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249
1083
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250 What is a mini-batch?
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251 ~~~~~~~~~~~~~~~~~~~~~
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252
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253 This is a follow-up to the meeting's discussion about whether a mini-batch
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254 returned by a dataset should be itself a dataset.
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255
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256 OD: During the meeting I was voting in favor of a 'yes', mostly because it
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257 made sense to me (a mini-batch is a subset of a dataset and thus should be a
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258 dataset), but now I tend towards 'no'. The main reason is it is not clear yet
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259 what the dataset interface will be, so that it is hard to judge whether this
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260 is good idea (my main concern is how much additional work would be required by
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261 the writer of a new dataset subclass). Anyway, maybe a first thing we could
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262 think about is what we want a mini-batch to be. I think we can agree that we
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263 would like to be able to do something like:
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264
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265 .. code-block:: python
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266
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267 for mb in dataset.mini_batches(size=10):
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268 learner.update(mb.input, mb.target)
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269
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270 so that it should be ok for a mini-batch to be an object whose fields
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271 (that should have the same name as those of the dataset) are numpy arrays.
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272 More generally, we would like to be able to iterate on samples in a
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273 mini-batch, or do random access on them, so a mini-batch should implement
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274 __iter__ and __getitem__.
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275 Besides this, is there any other typical use-case of a mini-batch? In
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276 particular, is there any reason to want an infinite mini-batch, or a very big
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277 mini-batch that may not fit in memory? (in which case we may need to revise
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278 our idea of what 'mini' means) Hopefully the answer to that last question is
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279 no, as I think it would definitely keep things simpler, since we could simply
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280 use numpy arrays (for numeric data) or lists (for anything else) to store
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281 mini-batches' data. So I vote for 'no'.
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282
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283 YB: I agree that a mini-batch should definitely be safely assumed
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284 to fit in memory. That makes it at least in principle semantically
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285 different from a dataset. But barring that restriction, it might
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286 share of the properties of a dataset.
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287
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288 A dataset is a learner
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289 ~~~~~~~~~~~~~~~~~~~~~~
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290
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291 OD: (this is hopefully a clearer re-write of the original version from
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292 r7e6e77d50eeb, which I was not happy with).
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293 There are typically three kinds of objects that spit out data:
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294
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295 1. Datasets that are loaded from disk or are able to generate data all by
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296 themselves (i.e. without any other dataset as input)
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297 2. Datasets that transform their input dataset in a way that only depends on
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298 the input dataset (e.g. filtering samples or features, normalizing data, etc.)
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299 3. Datasets that transform their input dataset in a way that is learned on a
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300 potentially different dataset (e.g. PCA when you want to learn the projection
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301 space on the training set in order to transform both the training and test
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302 sets).
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303
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304 My impression currently is that we would use dataset subclasses to handle 1
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305 and 2. However, 3 requires a learner framework, so you would need to have
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306 something like a LearnerOutputDataset(trained_learner, dataset).
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307
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308 Note however that 2 is a special case of 3 (where training does nothing), and
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309 1 is a special case of 2 (where we do not care about being given an input
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310 dataset). Thus you could decide to also implement 1 and 2 as learners wrapped
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311 by LearnerOutputDataset.
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312
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313 The main advantages I find in this approach (that I have been using at
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314 Ubisoft) are:
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315
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316 - You only need to learn how to subclass the learner class. The only dataset
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317 class is LearnerOutputDataset, which you could just name Dataset.
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318 - You do not have different ways to achieve the same result (having to figure
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319 out which one is most appropriate).
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320 - Upgrading code from 2 to 3 is more straighforward. Such a situation can
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321 happen e.g. if you write some code that normalizes your input dataset
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322 (situation 2), then realize later you would like to be able to normalize new
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323 datasets using the same parameters (e.g. same shift & rescaling), which
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324 requires situation 3.
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325 - It can make your life easier when thinking about how to plug things together
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326 (something that has not been discussed yet), because the interfaces of the
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327 various components are less varied.
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328
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329 I am not saying that we should necessarily do it this way, but I think it is
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330 worth at least keeping in mind this close relationship between simple
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331 processing and learning, and thinking about what are the benefits / drawbacks
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332 in keeping them separate in the class hierarchy.
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333
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334 RP: I actually like this idea of having the dataset implement the same
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335 interface as the learner ( or actually a subset of the interface .. ).
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336 I hope people decide to do this.
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337
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338 Support for shared variables
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339 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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340
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341 RP asks: What is the status of having the dataset support copying data
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342 on the GPU ( by storing data in shared variables) ? Have you decided to
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343 include this feature or not ? I think that the strongest selling point of
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344 Theano is that it runs on GPU transperently, and I see this as a good
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345 selling point for the library as well. Plus we intend to move more and
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346 more towards running things on GPU. If the dataset object does not support
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347 this feature we will need to find hacks around it ..
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348
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349 OD: I have like zero experience with GPU so hopefully someone else can answer
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350 this. But the way I see it, hopefully it could work by having some dataset
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351 object that would take care of storing its input data into a shared variable.
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352 OD (continued): After thinking a bit more about it, I am not sure that would
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353 work. I definitely need to look at some code doing it to get a better
75175e2e697d dataset: Continued comment about GPU and shared variables
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354 understanding of it, but my feeling is that you need your learner to be
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355 written in a specific way to achieve this, in which case it may be up to the
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356 learner to take its input data and store it into a shared variable.
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357
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358 RP comment: Yes, the dataset object alone can not handle this, the issue is somewhere
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359 between the dataset and the learner. Or in other words, everytime you change
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360 the data you need to recompile your theano function. So the learner can not
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361 only get data from the dataset, it needs to get a shared variable. The learner
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362 should also be aware when the dataset is changed, to recompile its internal
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363 functions. I'm not sure which is the best wa to do this. My personal feeling
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364 is that the dataset should be part of the learner. The lerner should provide
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365 a function use_dataset ( or replace_dataset). When this function is called,
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366 all the theano functions in the learner get recompiled based on shared
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367 variables that the dataset object provides. It sort of fits very well in the
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368 framework that I have in mind, which was spattered around in the learner.txt
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369 and some of my previous emails. I think it shares a lot with James concepts,
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370 since it follows quite closely the concepts behind Theano.
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371
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372 OD asks: Ok, so why would the dataset have to be responsible for providing a
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373 shared variable? Why wouldn't the learner just create this shared variable
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374 internally and copy into it the data provided by the dataset?
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375
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376 RP replies: Sure, the learner could take care of all this. Note though that the
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377 learner should take care to divide the dataset into chunks that fit in the
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378 GPU memory ( in case of a large dataset) and then take care of updating the
29b48deb6a84 reply/comment regarding the GPU and datasets
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1105
diff changeset
379 shared variables acording to the current chunk. Personally I feel like all
29b48deb6a84 reply/comment regarding the GPU and datasets
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1105
diff changeset
380 this data division, management and so on should be done by the dataset.
29b48deb6a84 reply/comment regarding the GPU and datasets
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1105
diff changeset
381 It feels more natural that way. For example assume you have a dataset that
29b48deb6a84 reply/comment regarding the GPU and datasets
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1105
diff changeset
382 is composed of a time series and some static data ( carre-tech heart beat
29b48deb6a84 reply/comment regarding the GPU and datasets
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1105
diff changeset
383 data is a good example). The static data is small enough so that you could
29b48deb6a84 reply/comment regarding the GPU and datasets
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1105
diff changeset
384 always store on the GPU, and you would only need to split the time series.
29b48deb6a84 reply/comment regarding the GPU and datasets
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1105
diff changeset
385 For the learner to do this ( since it gets the same interface from any
29b48deb6a84 reply/comment regarding the GPU and datasets
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1105
diff changeset
386 dataset object) would be like and if <this case> then, while for the
29b48deb6a84 reply/comment regarding the GPU and datasets
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1105
diff changeset
387 dataset is just a different class. But I'm happy to have all this GPU stuff
29b48deb6a84 reply/comment regarding the GPU and datasets
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1105
diff changeset
388 send to the learner as well if everybody else believe that is better.
29b48deb6a84 reply/comment regarding the GPU and datasets
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1105
diff changeset
389
1110
4797a4cb73e1 added comment to dataset.
Frederic Bastien <nouiz@nouiz.org>
parents: 1109
diff changeset
390 FB comment: I don't understand why you would need to recompile the theano function.
4797a4cb73e1 added comment to dataset.
Frederic Bastien <nouiz@nouiz.org>
parents: 1109
diff changeset
391 Their is 2 cases, the data is in a shared variable. You can directly change the data
4797a4cb73e1 added comment to dataset.
Frederic Bastien <nouiz@nouiz.org>
parents: 1109
diff changeset
392 in the shared variable without recompiling the theano fct. The second case is when
4797a4cb73e1 added comment to dataset.
Frederic Bastien <nouiz@nouiz.org>
parents: 1109
diff changeset
393 the dataset is in an ordinary theano variable. In that case, the first step in the
4797a4cb73e1 added comment to dataset.
Frederic Bastien <nouiz@nouiz.org>
parents: 1109
diff changeset
394 theano fct will be to transfer the dataset to the gpu before computation. If the data
4797a4cb73e1 added comment to dataset.
Frederic Bastien <nouiz@nouiz.org>
parents: 1109
diff changeset
395 change at each call, that will be as efficient as changing the data manually every time
4797a4cb73e1 added comment to dataset.
Frederic Bastien <nouiz@nouiz.org>
parents: 1109
diff changeset
396 in the shared variable.
1116
18a092001752 An idea about Datasets and GPU.
Arnaud Bergeron <abergeron@gmail.com>
parents: 1110
diff changeset
397
18a092001752 An idea about Datasets and GPU.
Arnaud Bergeron <abergeron@gmail.com>
parents: 1110
diff changeset
398 AB: I have an idea about this which kind of fits in the "building a
18a092001752 An idea about Datasets and GPU.
Arnaud Bergeron <abergeron@gmail.com>
parents: 1110
diff changeset
399 theano op" thing that we talked about at the last meeting.
18a092001752 An idea about Datasets and GPU.
Arnaud Bergeron <abergeron@gmail.com>
parents: 1110
diff changeset
400
1117
c1943feada10 Proposal for theano dataset wrapper. The details still have to be worked out.
Arnaud Bergeron <abergeron@gmail.com>
parents: 1116
diff changeset
401 We can just build a theano Op that wraps dataset objects and takes
c1943feada10 Proposal for theano dataset wrapper. The details still have to be worked out.
Arnaud Bergeron <abergeron@gmail.com>
parents: 1116
diff changeset
402 care of the details of tranferring data to the GPU or otherwise.
c1943feada10 Proposal for theano dataset wrapper. The details still have to be worked out.
Arnaud Bergeron <abergeron@gmail.com>
parents: 1116
diff changeset
403
c1943feada10 Proposal for theano dataset wrapper. The details still have to be worked out.
Arnaud Bergeron <abergeron@gmail.com>
parents: 1116
diff changeset
404 I have a prototype interface/implemantation in the shared_dataset.py
c1943feada10 Proposal for theano dataset wrapper. The details still have to be worked out.
Arnaud Bergeron <abergeron@gmail.com>
parents: 1116
diff changeset
405 file in this directory.
1127
7207f86a661f dataset: Comment on AB's idea to handle the GPU/shared variable issue
Olivier Delalleau <delallea@iro>
parents: 1124
diff changeset
406
7207f86a661f dataset: Comment on AB's idea to handle the GPU/shared variable issue
Olivier Delalleau <delallea@iro>
parents: 1124
diff changeset
407 OD: I like AB's approach.
7207f86a661f dataset: Comment on AB's idea to handle the GPU/shared variable issue
Olivier Delalleau <delallea@iro>
parents: 1124
diff changeset
408
1337
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Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
409
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
410 Data API proposal by Olivier D
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
411 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
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412
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
413 A single sample containing multiple fields (e.g. an input and a target part)
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
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414 is an object s that you can manipulate as follows:
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
415
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
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416 .. code-block:: python
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
417
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
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418 # Obtain actual data stored within `s` (e.g. a numpy vector). There is no
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
419 # guarantee that modifying the resulting data object will actually update
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
420 # the data stored in `s`.
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
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421 data = s()
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
422 # Create a sample that sees a field of `s`.
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
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423 input_part = s.input
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
424 # Obtain actual input data (e.g. as a numpy vector).
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
425 input_data = input_part()
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
426 # Create a sample that sees the i-th element of the data stored in `s`.
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
427 ith = s[i]
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
428 # This should not fail.
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
429 assert ith() == s()[i]
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
430 # You could also select a range.
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
431 i_to_j = s[i:j]
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
432 assert i_to_j() == s()[i:j]
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
433 # And actually do pretty much anything you want with __getitem__, as long
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
434 # as the underlying data stored in the sample supports it (for instance,
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
435 # here it should be at least a 3D tensor).
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
436 fancy_selection = s[i, :, j:k]
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
437 assert fancy_selection() == s()[i, :, j:k]
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
438 # Write some value (e.g. a numpy vector) into the sample. May raise an
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
439 # exception if the sample is in read-only mode.
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
440 s._write(val)
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
441 # Shortcut to write data into a field (same as `s.input._write(val)`).
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
442 s.input = val
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
443 # Basic mathematical operators.
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
444 s *= val
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
445 s += val
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
446 s -= val
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
447 s /= val
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
448 # Replace a field. Note that this is different from `s.input = val`
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
449 # because here `new_input` is a sample, not a numeric value: the current
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
450 # `s.input` will not be written to, instead it makes `s.input` point
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
451 # towards a different sample. This may lead to confusion, so a different
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
452 # syntax may be better (e.g. s._set_field('input', new_input)).
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
453 s.input = new_input
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
454 # The equality of two samples is defined by the equality of their
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
455 # underlying data.
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
456 def __eq__(self, other):
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
457 return self() == other()
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
458 # Iterate on fields (open question: should they be ordered?).
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
459 fields = dict([(name, sample) for name, sample in s._iter_fields()])
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
460 assert fields['input'] == s.input
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
461 # Iterating on a sample yields samples that see consecutive elements.
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
462 for sample, value in izip(s, s()):
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
463 assert sample() == value
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
464 # The length of a sample is the same as that of its underlying data.
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
465 assert len(s) == len(s())
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
466 # The shape of a sample is the same as that of its underlying data.
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
467 # Note that it only makes sense for tensor-like data.
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
468 assert s._shape() == s().shape
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
469 # The size of a sample is the product of its shape elements.
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
470 assert s._size() == reduce(operator.__mul__, s._shape())
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
471
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
472 All sample methods should start with '_', to differentiate them from the
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
473 sample's fields. This is a bit awkward, but I like the `sample.field` syntax
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
474 compared to something like "sample.get_field('field')", which makes code less
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
475 readable, especially when combining with sub_fields, e.g. `sample.input.x1`
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
476 vs. sample.get_field('input').get_field('x1').
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
477
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
478 The extension from sample to dataset is actually to use the same class, but
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
479 with the convention that the first "dimension" in the data seen by the dataset
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
480 corresponds to the samples' indices in the dataset.
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
481
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
482 .. code-block:: python
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
483
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
484 # Return data stored in dataset `d` (e.g. a numpy matrix).
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
485 data = d()
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
486 # Return the i-th sample in the dataset.
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Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
487 s = d[i]
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
488 # Data should match!
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
489 assert data[i] == s()
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
490 # Return a subset of the dataset.
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
491 sub_data = d[i:j]
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
492 # Advanced indexing.
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
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493 sub_data = d[some_list_of_indices]
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
494 # Dataset that sees the input part only.
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
495 input_part = d.input
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
496 # Dataset such that its i-th element is data[i][something] (see the sample
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
497 # examples for what `something` may be).
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
498 some_sub_data = d[:, something]
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
499 # The following should not fail.
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
500 assert d[i, something] == d[i][something] # == some_sub_data[i]
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
501 # You can also write into a dataset.
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
502 d._write(val)
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
503 d.input = val
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
504 # Center dataset in-place (requires `d` not to be read-only).
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
505 d -= numpy.mean(d())
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
506 # The length of a dataset is its number of samples.
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
507 n_samples = len(d)
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
508 # The width of a dataset (if it exists) is the length of its samples.
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
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diff changeset
509 assert d._shape()[1] == len(d[0]) # == d._width() (shortcut)
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
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510 # Iterating on a dataset yields individual samples.
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
511 for i, sample in enumerate(d):
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
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parents: 1190
diff changeset
512 assert d[i] == sample
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
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parents: 1190
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513 # It is allowed for a dataset to hold heterogeneous data. For instance
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
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514 # you could have
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
515 len(d.data1) != len(d.data2)
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
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516 # A sample in the dataset is not required to inherit all the dataset's
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
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parents: 1190
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517 # fields, for instance in the case above you could decide that the dataset
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
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518 # sees the same data as its first sub-dataset, i.e.
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
519 d[i] == d.data1[i]
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
520
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
521 There remain some fuzzy points. For instance, are fields allowed to overlap?
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
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522 (e.g. so that one could write both s.pos_3d to get the 3d vector coordinate of
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
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parents: 1190
diff changeset
523 sample s, and s.x to get the x coordinate without being forced to go through
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
524 s.pos_3d.x). What are the fields of s[i:j] if the (i, j) range does not
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
525 exactly match a subset of fields? How do we handle metadata? (e.g. if we want
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
526 to describe the dataset to say it contains 28x28 image data, so that an
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
527 algorithm for filter visualization can automatically deal with it)
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
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528
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
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diff changeset
529 Now, on to some use cases.
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
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parents: 1190
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530
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
531 .. code-block:: python
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
532
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
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533 # Mini-batches.
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
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534 mb_dataset = d._minibatches(batch_size=5)
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
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parents: 1190
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535 # The mini-batch dataset views samples that are mini-batches.
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
536 assert mb_dataset[0]() == d[0:5]() # As long as len(d) >= 5.
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
537
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
538 # Shuffling samples.
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
539 random_indices = range(len(d))
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
540 random_indices = numpy.random.shuffle(random_indices)
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
541 shuffled_dataset = d[random_indices]
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
542
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
543 # Typical linear regression with stochastic gradient descent.
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
544 n_inputs = d.input._width()
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
545 n_targets = d.target._width()
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
546 weights = numpy.zeros((n_inputs, n_targets))
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
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547 bias = numpy.zeros(n_targets)
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
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548 mb_dataset = d._minibatches(batch_size=10)
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
549 # Note: it is important to get the number of inputs / targets
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
550 # before converting to minibatches, because
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
551 # mb_dataset.input._width() == 10
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
552 # since this is the length of a minibatch matrix. However you
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
553 # could still do the following, which is less readable:
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
554 # n_inputs = mb_dataset.input._shape()[2]
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
555 # You could also wait until you see the first sample to create
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
556 # the parameters (this would actually be a better way to do it, since
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
557 # it avoids calling the _width method).
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
558 for input, target in izip(mb_dataset.input, mb_dataset.target):
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
559 cost = (numpy.dot(input(), weights) + b - target())**2
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
560 # Update weights and bias depending on cost....
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
561
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
562 A few more points:
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
563 - Infinite datasets could be used (would just need to define a convention
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
564 on what __len__ should do).
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
565 - It is also ok to have datasets that do not support random access (so the
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
566 only way to access samples is through iteration).
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
567 - Ideally, data should be deterministic (i.e. __call__() should always
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
568 return the same thing). It would probably be up to the user to be super
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
569 careful if he decides to use a non-deterministic dataset.
1338
91637815b7ca Added a comment on the dataset vs. task issue
Olivier Delalleau <delallea@iro>
parents: 1337
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570 - About the "task vs. dataset" distinction. This could be achieved by
91637815b7ca Added a comment on the dataset vs. task issue
Olivier Delalleau <delallea@iro>
parents: 1337
diff changeset
571 associating to a task the names of the fields it requires (e.g. "input"
91637815b7ca Added a comment on the dataset vs. task issue
Olivier Delalleau <delallea@iro>
parents: 1337
diff changeset
572 and "target" for the regression task), and if the dataset does not
91637815b7ca Added a comment on the dataset vs. task issue
Olivier Delalleau <delallea@iro>
parents: 1337
diff changeset
573 already defines these fields, using a dataset wrapper than does it
91637815b7ca Added a comment on the dataset vs. task issue
Olivier Delalleau <delallea@iro>
parents: 1337
diff changeset
574 (saying for instance that "input" is the concatenation of "x1" and "x2",
91637815b7ca Added a comment on the dataset vs. task issue
Olivier Delalleau <delallea@iro>
parents: 1337
diff changeset
575 and "target" is "y", for a dataset whose fields are x1, x2 and y).
1337
7dfc3d3052ea Added proposal for dataset API as discussed on pylearn-dev
Olivier Delalleau <delallea@iro>
parents: 1190
diff changeset
576
1339
158493f8dff9 comment on dataset proposal by Olivier
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1338
diff changeset
577
158493f8dff9 comment on dataset proposal by Olivier
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1338
diff changeset
578 RP comments:
158493f8dff9 comment on dataset proposal by Olivier
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1338
diff changeset
579 - I like this approach. I think having overlapping fields might be useful.
158493f8dff9 comment on dataset proposal by Olivier
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1338
diff changeset
580 I would add that I was thinking of a way to look at one's results. Is
158493f8dff9 comment on dataset proposal by Olivier
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1338
diff changeset
581 something I've been faced with, say you run 500 jobs and then you want to
158493f8dff9 comment on dataset proposal by Olivier
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1338
diff changeset
582 understand those jobs' results. Looking just at the best performing seems a waste, and
158493f8dff9 comment on dataset proposal by Olivier
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1338
diff changeset
583 there is a lot more information you can extract from your results if you are
158493f8dff9 comment on dataset proposal by Olivier
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1338
diff changeset
584 able to generate certain plots or statistics. To do this you would need to
158493f8dff9 comment on dataset proposal by Olivier
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1338
diff changeset
585 get the data in ipython (or something quite similar) where you have available
158493f8dff9 comment on dataset proposal by Olivier
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1338
diff changeset
586 the needed functions to plot different things, generate different tables. The
158493f8dff9 comment on dataset proposal by Olivier
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1338
diff changeset
587 point that I was trying to make is that you can get those results in
158493f8dff9 comment on dataset proposal by Olivier
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1338
diff changeset
588 something that has this very API that Olivier described. This way both both
158493f8dff9 comment on dataset proposal by Olivier
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1338
diff changeset
589 your input data and your results will be in the same form and whatever
158493f8dff9 comment on dataset proposal by Olivier
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1338
diff changeset
590 visualization functions you have for your results you can use on your data as
158493f8dff9 comment on dataset proposal by Olivier
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1338
diff changeset
591 well. For this you would need a bit more flexibility, in the sense that if
158493f8dff9 comment on dataset proposal by Olivier
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1338
diff changeset
592 you have some data d, you should be able to put constraints on it, like
158493f8dff9 comment on dataset proposal by Olivier
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1338
diff changeset
593 d.some_field == 5 means all entries in d that has some_field == 5, or
158493f8dff9 comment on dataset proposal by Olivier
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1338
diff changeset
594 d.some_field > 5. You would also not use psql anymore but this console,
158493f8dff9 comment on dataset proposal by Olivier
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1338
diff changeset
595 which would collect the results for you from sql, and give them to you as
158493f8dff9 comment on dataset proposal by Olivier
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1338
diff changeset
596 data object.
158493f8dff9 comment on dataset proposal by Olivier
Razvan Pascanu <r.pascanu@gmail.com>
parents: 1338
diff changeset
597
1340
04b988fb00b6 Reply to Razvan
Olivier Delalleau <delallea@iro>
parents: 1339
diff changeset
598 OD replies: Actually this should be doable with (almost) what I wrote above,
04b988fb00b6 Reply to Razvan
Olivier Delalleau <delallea@iro>
parents: 1339
diff changeset
599 due to the way numpy redefines ==, >, etc. (which btw should break some of my
04b988fb00b6 Reply to Razvan
Olivier Delalleau <delallea@iro>
parents: 1339
diff changeset
600 assertions above, since I had forgotten about this). If you replace e.g. my
04b988fb00b6 Reply to Razvan
Olivier Delalleau <delallea@iro>
parents: 1339
diff changeset
601 implementation of __eq__ above by the following:
04b988fb00b6 Reply to Razvan
Olivier Delalleau <delallea@iro>
parents: 1339
diff changeset
602
04b988fb00b6 Reply to Razvan
Olivier Delalleau <delallea@iro>
parents: 1339
diff changeset
603 .. code-block:: python
04b988fb00b6 Reply to Razvan
Olivier Delalleau <delallea@iro>
parents: 1339
diff changeset
604
04b988fb00b6 Reply to Razvan
Olivier Delalleau <delallea@iro>
parents: 1339
diff changeset
605 def __eq__(self, other):
04b988fb00b6 Reply to Razvan
Olivier Delalleau <delallea@iro>
parents: 1339
diff changeset
606 return other == self()
04b988fb00b6 Reply to Razvan
Olivier Delalleau <delallea@iro>
parents: 1339
diff changeset
607
04b988fb00b6 Reply to Razvan
Olivier Delalleau <delallea@iro>
parents: 1339
diff changeset
608 Here, `self` is a dataset that represents some numpy vector data. Then whether
04b988fb00b6 Reply to Razvan
Olivier Delalleau <delallea@iro>
parents: 1339
diff changeset
609 `other` is another dataset or a numpy vector or some scalar, this will return
04b988fb00b6 Reply to Razvan
Olivier Delalleau <delallea@iro>
parents: 1339
diff changeset
610 a numpy boolean vector (the result of the comparison made by numpy). We may
04b988fb00b6 Reply to Razvan
Olivier Delalleau <delallea@iro>
parents: 1339
diff changeset
611 support boolean vectors in advanced indexing, so you could do
04b988fb00b6 Reply to Razvan
Olivier Delalleau <delallea@iro>
parents: 1339
diff changeset
612 d[d.some_field == 5]
04b988fb00b6 Reply to Razvan
Olivier Delalleau <delallea@iro>
parents: 1339
diff changeset
613 and obtain the subset of `d` whose samples have `some_field` set to 5.
04b988fb00b6 Reply to Razvan
Olivier Delalleau <delallea@iro>
parents: 1339
diff changeset
614 Same could be done with __lt__, __le__, etc.
04b988fb00b6 Reply to Razvan
Olivier Delalleau <delallea@iro>
parents: 1339
diff changeset
615