Mercurial > pylearn
annotate learner.py @ 242:ef70a665aaaf
Hmm... that was committed by Fred I think, I got lost by Mercurial I think
author | delallea@opale.iro.umontreal.ca |
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date | Fri, 30 May 2008 10:19:16 -0400 |
parents | bd728c83faff |
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3 from exceptions import * |
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4 from dataset import AttributesHolder |
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5 |
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6 class LearningAlgorithm(object): |
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7 """ |
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8 Base class for learning algorithms, provides an interface |
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9 that allows various algorithms to be applicable to generic learning |
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10 algorithms. It is only given here to define the expected semantics. |
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11 |
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12 A L{Learner} can be seen as a learning algorithm, a function that when |
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13 applied to training data returns a learned function (which is an object that |
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14 can be applied to other data and return some output data). |
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15 |
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16 There are two main ways of using a learning algorithms, and some learning |
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17 algorithms only support one of them. The first is the way of the standard |
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18 machine learning framework, in which a learning algorithm is applied |
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19 to a training dataset, |
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20 |
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21 model = learning_algorithm(training_set) |
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22 |
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23 resulting in a fully trained model that can be applied to another dataset: |
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24 |
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25 output_dataset = model(input_dataset) |
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26 |
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27 Note that the application of a dataset has no side-effect on the model. |
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28 In that example, the training set may for example have 'input' and 'target' |
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29 fields while the input dataset may have only 'input' (or both 'input' and |
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30 'target') and the output dataset would contain some default output fields defined |
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31 by the learning algorithm (e.g. 'output' and 'error'). |
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32 |
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33 The second way of using a learning algorithm is in the online or |
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34 adaptive framework, where the training data are only revealed in pieces |
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35 (maybe one example or a batch of example at a time): |
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36 |
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37 model = learning_algorithm() |
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38 |
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39 results in a fresh model. The model can be adapted by presenting |
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40 it with some training data, |
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41 |
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42 model.update(some_training_data) |
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43 ... |
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44 model.update(some_more_training_data) |
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45 ... |
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46 model.update(yet_more_training_data) |
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47 |
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48 and at any point one can use the model to perform some computation: |
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49 |
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50 output_dataset = model(input_dataset) |
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51 |
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52 """ |
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53 |
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54 def __init__(self): pass |
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55 |
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56 def __call__(self, training_dataset=None): |
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57 """ |
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58 Return a LearnerModel, either fresh (if training_dataset is None) or fully trained (otherwise). |
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59 """ |
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60 raise AbstractFunction() |
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61 |
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62 class LearnerModel(AttributesHolder): |
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63 """ |
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64 LearnerModel is a base class for models returned by instances of a LearningAlgorithm subclass. |
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65 It is only given here to define the expected semantics. |
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66 """ |
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67 def __init__(self): |
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68 pass |
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69 |
14 | 70 def update(self,training_set,train_stats_collector=None): |
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71 """ |
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72 Continue training a learner, with the evidence provided by the given training set. |
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73 Hence update can be called multiple times. This is the main method used for training in the |
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74 on-line setting or the sequential (Bayesian or not) settings. |
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75 |
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76 This function has as side effect that self(data) will behave differently, |
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77 according to the adaptation achieved by update(). |
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78 |
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79 The user may optionally provide a training L{StatsCollector} that is used to record |
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80 some statistics of the outputs computed during training. It is update(d) during |
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81 training. |
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82 """ |
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83 raise AbstractFunction() |
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84 |
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85 def __call__(self,input_dataset,output_fieldnames=None, |
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86 test_stats_collector=None,copy_inputs=False, |
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87 put_stats_in_output_dataset=True, |
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88 output_attributes=[]): |
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89 """ |
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90 A trained or partially trained L{Model} can be used with |
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91 with one or more calls to it. The argument is an input L{DataSet} (possibly |
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92 containing a single example) and the result is an output L{DataSet} of the same length. |
128 | 93 If output_fieldnames is specified, it may be use to indicate which fields should |
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94 be constructed in the output L{DataSet} (for example ['output','classification_error']). |
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95 Otherwise, some default output fields are produced (possibly depending on the input |
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96 fields available in the input_dataset). |
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97 Optionally, if copy_inputs, the input fields (of the input_dataset) can be made |
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98 visible in the output L{DataSet} returned by this method. |
128 | 99 Optionally, attributes of the learner can be copied in the output dataset, |
100 and statistics computed by the stats collector also put in the output dataset. | |
101 Note the distinction between fields (which are example-wise quantities, e.g. 'input') | |
102 and attributes (which are not, e.g. 'regularization_term'). | |
110
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103 """ |
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104 raise AbstractFunction() |