annotate learner.py @ 229:d7250ee86f72

Added speed test for ArraDataSet
author Frederic Bastien <bastienf@iro.umontreal.ca>
date Fri, 16 May 2008 16:40:26 -0400
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children 50a8302addaf
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2 from exceptions import *
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5 class LearningAlgorithm(object):
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6 """
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7 Base class for learning algorithms, provides an interface
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8 that allows various algorithms to be applicable to generic learning
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9 algorithms. It is only given here to define the expected semantics.
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11 A L{Learner} can be seen as a learning algorithm, a function that when
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12 applied to training data returns a learned function (which is an object that
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13 can be applied to other data and return some output data).
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15 There are two main ways of using a learning algorithms, and some learning
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16 algorithms only support one of them. The first is the way of the standard
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17 machine learning framework, in which a learning algorithm is applied
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18 to a training dataset,
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19
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20 model = learning_algorithm(training_set)
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22 resulting in a fully trained model that can be applied to another dataset:
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24 output_dataset = model(input_dataset)
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25
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26 Note that the application of a dataset has no side-effect on the model.
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27 In that example, the training set may for example have 'input' and 'target'
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28 fields while the input dataset may have only 'input' (or both 'input' and
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29 'target') and the output dataset would contain some default output fields defined
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30 by the learning algorithm (e.g. 'output' and 'error').
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32 The second way of using a learning algorithm is in the online or
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33 adaptive framework, where the training data are only revealed in pieces
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34 (maybe one example or a batch of example at a time):
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36 model = learning_algorithm()
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37
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38 results in a fresh model. The model can be adapted by presenting
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39 it with some training data,
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41 model.update(some_training_data)
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42 ...
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43 model.update(some_more_training_data)
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44 ...
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45 model.update(yet_more_training_data)
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46
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47 and at any point one can use the model to perform some computation:
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49 output_dataset = model(input_dataset)
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51 """
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53 def __init__(self): pass
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54
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55 def __call__(self, training_dataset=None):
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56 """
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57 Return a LearnerModel, either fresh (if training_dataset is None) or fully trained (otherwise).
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58 """
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59 raise AbstractFunction()
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60
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61 class LearnerModel(AttributesHolder):
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62 """
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63 LearnerModel is a base class for models returned by instances of a LearningAlgorithm subclass.
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64 It is only given here to define the expected semantics.
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65 """
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66 def __init__(self):
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67 pass
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68
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69 def update(self,training_set,train_stats_collector=None):
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70 """
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71 Continue training a learner, with the evidence provided by the given training set.
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72 Hence update can be called multiple times. This is the main method used for training in the
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73 on-line setting or the sequential (Bayesian or not) settings.
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75 This function has as side effect that self(data) will behave differently,
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76 according to the adaptation achieved by update().
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78 The user may optionally provide a training L{StatsCollector} that is used to record
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79 some statistics of the outputs computed during training. It is update(d) during
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80 training.
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81 """
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82 raise AbstractFunction()
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83
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84 def __call__(self,input_dataset,output_fieldnames=None,
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85 test_stats_collector=None,copy_inputs=False,
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86 put_stats_in_output_dataset=True,
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87 output_attributes=[]):
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88 """
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89 A trained or partially trained L{Model} can be used with
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90 with one or more calls to it. The argument is an input L{DataSet} (possibly
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91 containing a single example) and the result is an output L{DataSet} of the same length.
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92 If output_fieldnames is specified, it may be use to indicate which fields should
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93 be constructed in the output L{DataSet} (for example ['output','classification_error']).
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94 Otherwise, some default output fields are produced (possibly depending on the input
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95 fields available in the input_dataset).
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96 Optionally, if copy_inputs, the input fields (of the input_dataset) can be made
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97 visible in the output L{DataSet} returned by this method.
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98 Optionally, attributes of the learner can be copied in the output dataset,
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99 and statistics computed by the stats collector also put in the output dataset.
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100 Note the distinction between fields (which are example-wise quantities, e.g. 'input')
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101 and attributes (which are not, e.g. 'regularization_term').
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102 """
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103 raise AbstractFunction()