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Yaml tutorial - part of pylearn2 experience¶

In [5]:

import numpy as np
import cPickle
from pylearn2.config import yaml_parse

## AutoEncoder Class Example class AutoEncoder(object): def __init__(self, nvis, nhid, iscale = 0.1, activation_fn = np.tanh, params = None): self.nvis = nvis self.nhid = nhid self.activation_fn = activation_fn if params is None: self.W = iscale * np.random.randn(nvis, nhid) self.bias_vis = np.zeros(nvis) self.bias_hid = np.zeros(nhid) else: self.W, self.bias_vis, self.bias_hid = W print self def __str__(self): model_str = '%s\n' % self.__class__.__name__ model_str += '\tnvis = %i\n' % self.nvis model_str += '\tnhid = %i\n' % self.nhid model_str += '\tactivation_fn = %s\n' % str(self.activation_fn) model_str += '\tmean std(weigths) = %.2f\n' % self.W.std(axis=0).mean() return model_str def save(self, fname): with open(fname, 'w') as f: cPickle.dump([self.W, self.bias_vis, self.bias_hid], f)

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## example
import yaml_autoencoder
reload(yaml_autoencoder)
ae = yaml_autoencoder.AutoEncoder(nvis = 32 * 32, nhid = 50)

AutoEncoder
	nvis = 1024
	nhid = 50
	activation_fn = <ufunc 'tanh'>
	mean std(weigths) = 0.10

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## object instantiation with !obj yaml syntax
## UNFORTUNATELY it doesnt work with ipython notebook
## PUT THE CLASS IN A MODULE 
## NO WHITE SPACE ALLOWED between !obj and : and class
## THERE MUST BE A DELIMITER BETWEEN CLASS NAME AND {
## NO ARITHMETIC allowed

## The !obj tag does two things. 
## Starting from the top-level package or module, it recursively imports all other sub-packages, 
## until it imports the final module. For this to succeed, 
## the top-level package should be located in one of the directories listed in the PYTHONPATH environment variable, 
## i.e. import <package> should succeed from a vanilla python shell. 
## Once the import phase is finished, it then proceeds to instantiate an object of type <object>, 
## whose parameters are given in the keyword style syntax.
yaml1 = """!obj:yaml_autoencoder.AutoEncoder {
    "nvis": 784,
    "nhid": 100,
    "iscale": 0.2,
}
"""
print yaml1
model1 = yaml_parse.load(yaml1) ## either yaml string or yaml file stream

!obj:yaml_autoencoder.AutoEncoder {
    "nvis": 784,
    "nhid": 100,
    "iscale": 0.2,
}

AutoEncoder
	nvis = 784
	nhid = 100
	activation_fn = <ufunc 'tanh'>
	mean std(weigths) = 0.20

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## Anchors and References
## Anchors associate a unique identifier to a given attribute or object defined in a yaml file. 
## This identifier can then be referenced in another section, 
## either to avoid duplicating code or when references to the same object are required. 
## Note that references are limited to anchors within the same yaml file.
## More interestingly, when anchors are applied to objects, 
## as in &model !obj:yaml_tutorial.autoencoder.AutoEncoder, 
## subsequent use of *model will create a pointer to the AutoEncoder object already instantiated by the anchor.

yaml2 = """
!obj:yaml_autoencoder.AutoEncoder {
    "nvis": &nvis 100,
    "nhid": *nvis,
}
"""
model2 = yaml_parse.load(yaml2)

AutoEncoder
	nvis = 100
	nhid = 100
	activation_fn = <ufunc 'tanh'>
	mean std(weigths) = 0.10

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## Dynamic includes (functions) with !import
## The !import tag is similar to !obj, 
## in that it also recursively imports packages, subpackages and modules. 
## It does not however instantiate any object. 
## The end result is thus a pointer to the symbol (package, module or function) specified by the tag.
yaml3 = """!obj:yaml_autoencoder.AutoEncoder {
    "nvis": 784,
    "nhid": 100,
    "iscale": 1.0,
    "activation_fn": !import 'pylearn2.expr.nnet.sigmoid_numpy'
}
"""
model3 = yaml_parse.load(yaml3)
model3.save('yaml_model3.pkl')

AutoEncoder
	nvis = 784
	nhid = 100
	activation_fn = <function sigmoid_numpy at 0x10d70d050>
	mean std(weigths) = 1.00

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## Loading files through Pickle
## !pkl which allows the end-user to dynamically load the contents of a pickle file. 
## This can be especially useful when initializing the parameters of a model from a pickled model instance 
## or or to load a dataset stored to disk in pickle format.
yaml4 = """
!obj:yaml_autoencoder.AutoEncoder {
    "nvis": 784,
    "nhid": 100,
    "iscale": 0.1,
    "params": !pkl: 'yaml_model3.pkl'
}
"""
model4 = yaml_parse.load(yaml4)

AutoEncoder
	nvis = 784
	nhid = 100
	activation_fn = <ufunc 'tanh'>
	mean std(weigths) = 1.00

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## Putting it all together
## In the same way that !import or !pkl can be used to define the “value” of a keyword attribute, 
## we can also use the !obj tag to instantiate objects as member attributes of another object.

## Since Pylearn2 experiments are themselves objects of the type pylearn2.train.Train, which combine:
## - a dataset, of type pylearn2.datasets.dataset.Dataset
## - a model, of type pylearn2.models.model.Model
## - a training algorithm, of type pylearn2.training_algorithms.training_algorithm.TrainingAlgorithm