class TrainTestSplitter(object):
"""
A generic class for splitting data into (random) subsets.
Parameters
----------
shuffle : bool, optional
Whether to shuffle the data.
random_seed : None or int, optional
Pseudo-random number generator seed used for random sampling.
Examples
--------
>>> import numpy as np
>>> y = np.array([1, 1, 2, 2, 3, 3, 3])
>>> tts1 = TrainTestSplitter(shuffle=False)
>>> train, test = tts1.split(y, train_ratio=0.5)
>>> print y[train], y[test]
[1 1 2] [2 3 3 3]
>>> train, test = tts1.split(y, train_ratio=0.5, stratify=True)
>>> print y[train], y[test]
[1 2 3] [1 2 3 3]
>>> for fold in tts1.make_k_folds(y, n_folds=3):
... print y[fold]
[1 1 2]
[2 3]
[3 3]
>>> for fold in tts1.make_k_folds(y, n_folds=3, stratify=True):
... print y[fold]
[1 2 3]
[1 2 3]
[3]
>>> for train, test in tts1.k_fold_split(y, n_splits=3):
... print y[train], y[test]
[2 3 3 3] [1 1 2]
[1 1 2 3 3] [2 3]
[1 1 2 2 3] [3 3]
>>> for train, test in tts1.k_fold_split(y, n_splits=3, stratify=True):
... print y[train], y[test]
[1 2 3 3] [1 2 3]
[1 2 3 3] [1 2 3]
[1 2 3 1 2 3] [3]
>>> tts2 = TrainTestSplitter(shuffle=True, random_seed=1337)
>>> train, test = tts2.split(y, train_ratio=0.5)
>>> print y[train], y[test]
[3 2 1] [2 1 3 3]
>>> train, test = tts2.split(y, train_ratio=0.5, stratify=True)
>>> print y[train], y[test]
[3 1 2] [3 3 2 1]
>>> for fold in tts2.make_k_folds(y, n_folds=3):
... print y[fold]
[3 2 1]
[2 1]
[3 3]
>>> for fold in tts2.make_k_folds(y, n_folds=3, stratify=True):
... print y[fold]
[3 1 2]
[3 2 1]
[3]
"""
def __init__(self, shuffle=False, random_seed=None):
self.shuffle = shuffle
self.random_seed = random_seed
self.rng = RNG(self.random_seed)
def split(self, y, train_ratio=0.8, stratify=False):
"""
Split data into train and test subsets.
Parameters
----------
y : (n_samples,) array-like
The target variable for supervised learning problems.
train_ratio : float, 0 < `train_ratio` < 1, optional
the proportion of the dataset to include in the train split.
stratify : bool, optional
If True, the folds are made by preserving the percentage of samples
for each class. Stratification is done based upon the `y` labels.
Returns
-------
train : (n_train,) np.ndarray
The training set indices for that split.
test : (n_samples - n_train,) np.ndarray
The testing set indices for that split.
"""
self.rng.reseed()
n = len(y)
if not stratify:
indices = self.rng.permutation(n) if self.shuffle else np.arange(
n, dtype=np.int)
train_size = int(train_ratio * n)
return np.split(indices, (train_size, ))
# group indices by label
labels_indices = {}
for index, label in enumerate(y):
if not label in labels_indices: labels_indices[label] = []
labels_indices[label].append(index)
train, test = np.array([], dtype=np.int), np.array([], dtype=np.int)
for label, indices in sorted(labels_indices.items()):
size = int(train_ratio * len(indices))
train = np.concatenate((train, indices[:size]))
test = np.concatenate((test, indices[size:]))
if self.shuffle:
self.rng.shuffle(train)
self.rng.shuffle(test)
return train, test
def make_k_folds(self, y, n_folds=3, stratify=False):
"""
Split data into folds of (approximately) equal size.
Parameters
----------
y : (n_samples,) array-like
The target variable for supervised learning problems.
Stratification is done based upon the `y` labels.
n_folds : int, `n_folds` > 1, optional
Number of folds.
stratify : bool, optional
If True, the folds are made by preserving the percentage of samples
for each class. Stratification is done based upon the `y` labels.
Yields
------
fold : np.ndarray
Indices for current fold.
"""
self.rng.reseed()
n = len(y)
if not stratify:
indices = self.rng.permutation(n) if self.shuffle else np.arange(
n, dtype=np.int)
for fold in np.array_split(indices, n_folds):
yield fold
return
# group indices
labels_indices = {}
for index, label in enumerate(y):
if isinstance(label, np.ndarray):
label = tuple(label.tolist())
if not label in labels_indices:
labels_indices[label] = []
labels_indices[label].append(index)
# split all indices label-wisely
for label, indices in sorted(labels_indices.items()):
labels_indices[label] = np.array_split(indices, n_folds)
# collect respective splits into folds and shuffle if needed
for k in xrange(n_folds):
fold = np.concatenate(
[indices[k] for _, indices in sorted(labels_indices.items())])
if self.shuffle:
self.rng.shuffle(fold)
yield fold
def k_fold_split(self, y, n_splits=3, stratify=False):
"""
Split data into train and test subsets for K-fold CV.
Parameters
----------
y : (n_samples,) array-like
The target variable for supervised learning problems.
Stratification is done based upon the `y` labels.
n_splits : int, `n_splits` > 1, optional
Number of folds.
stratify : bool, optional
If True, the folds are made by preserving the percentage of samples
for each class. Stratification is done based upon the `y` labels.
Yields
------
train : (n_train,) np.ndarray
The training set indices for current split.
test : (n_samples - n_train,) np.ndarray
The testing set indices for current split.
"""
folds = list(self.make_k_folds(y, n_folds=n_splits, stratify=stratify))
for i in xrange(n_splits):
yield np.concatenate(folds[:i] + folds[(i + 1):]), folds[i]
class RBM(BaseEstimator):
"""
Examples
--------
>>> X = RNG(seed=1337).rand(32, 256)
>>> rbm = RBM(n_hidden=100,
... k=4,
... batch_size=2,
... n_epochs=50,
... learning_rate='0.05->0.005',
... momentum='0.5->0.9',
... verbose=True,
... early_stopping=5,
... random_seed=1337)
>>> rbm
RBM(W=None, batch_size=2, best_W=None, best_epoch=None, best_hb=None,
best_recon=inf, best_vb=None, early_stopping=5, epoch=0, hb=None, k=4,
learning_rate='0.05->0.005', momentum='0.5->0.9', n_epochs=50,
n_hidden=100, persistent=True, random_seed=1337, vb=None, verbose=True)
"""
def __init__(self,
n_hidden=256,
persistent=True,
k=1,
batch_size=10,
n_epochs=10,
learning_rate=0.1,
momentum=0.9,
early_stopping=None,
verbose=False,
random_seed=None):
self.n_hidden = n_hidden
self.persistent = persistent
self.k = k # k in CD-k / PCD-k
self.batch_size = batch_size
self.n_epochs = n_epochs
self.learning_rate = learning_rate
self._learning_rate = None
self.momentum = momentum
self._momentum = None
self.early_stopping = early_stopping
self._early_stopping = self.early_stopping
self.verbose = verbose
self.random_seed = random_seed
self.W = None
self.vb = None # visible units bias
self.hb = None # hidden units bias
self.epoch = 0
self.best_W = None
self.best_vb = None
self.best_hb = None
self.best_epoch = None
self.best_recon = np.inf
self._dW = None
self._dvb = None
self._dhb = None
self._rng = None
self._persistent = None
self._initialized = False
super(RBM, self).__init__(_y_required=False)
def propup(self, v):
"""Propagate visible units activation upwards to the hidden units."""
z = np.dot(v, self.W) + self.hb
return sigmoid(z)
def sample_h_given_v(self, v0_sample):
"""Infer state of hidden units given visible units."""
h1_mean = self.propup(v0_sample)
h1_sample = self._rng.binomial(size=h1_mean.shape, n=1, p=h1_mean)
return h1_mean, h1_sample
def propdown(self, h):
"""Propagate hidden units activation downwards to the visible units."""
z = np.dot(h, self.W.T) + self.vb
return sigmoid(z)
def sample_v_given_h(self, h0_sample):
"""Infer state of visible units given hidden units."""
v1_mean = self.propdown(h0_sample)
v1_sample = self._rng.binomial(size=v1_mean.shape, n=1, p=v1_mean)
return v1_mean, v1_sample
def gibbs_hvh(self, h0_sample):
"""Performs a step of Gibbs sampling starting from the hidden units."""
v1_mean, v1_sample = self.sample_v_given_h(h0_sample)
h1_mean, h1_sample = self.sample_h_given_v(v1_sample)
return v1_mean, v1_sample, h1_mean, h1_sample
def gibbs_vhv(self, v0_sample):
"""Performs a step of Gibbs sampling starting from the visible units."""
raise NotImplementedError()
def free_energy(self, v_sample):
"""Function to compute the free energy."""
raise NotImplementedError()
def update(self, X_batch):
# compute positive phase
ph_mean, ph_sample = self.sample_h_given_v(X_batch)
# decide how to initialize chain
if self._persistent is not None:
chain_start = self._persistent
else:
chain_start = ph_sample
# gibbs sampling
for step in xrange(self.k):
nv_means, nv_samples, \
nh_means, nh_samples = self.gibbs_hvh(chain_start if step == 0 else nh_samples)
# update weights
self._dW = self._momentum * self._dW + \
np.dot(X_batch.T, ph_mean) - np.dot(nv_samples.T, nh_means)
self._dvb = self._momentum * self._dvb +\
np.mean(X_batch - nv_samples, axis=0)
self._dhb = self._momentum * self._dhb +\
np.mean(ph_mean - nh_means, axis=0)
self.W += self._learning_rate * self._dW
self.vb += self._learning_rate * self._dvb
self.hb += self._learning_rate * self._dhb
# remember state if needed
if self.persistent:
self._persistent = nh_samples
return np.mean(np.square(X_batch - nv_means))
def batch_iter(self, X):
n_batches = len(X) / self.batch_size
for i in xrange(n_batches):
start = i * self.batch_size
end = start + self.batch_size
X_batch = X[start:end]
yield X_batch
if n_batches * self.batch_size < len(X):
yield X[end:]
def train_epoch(self, X):
mean_recons = []
for i, X_batch in enumerate(self.batch_iter(X)):
mean_recons.append(self.update(X_batch))
if self.verbose and i % (len(X) / (self.batch_size * 16)) == 0:
print_inline('.')
if self.verbose: print_inline(' ')
return np.mean(mean_recons)
def _fit(self, X):
if not self._initialized:
layer = FullyConnected(self.n_hidden,
bias=0.,
random_seed=self.random_seed)
layer.setup_weights(X.shape)
self.W = layer.W
self.vb = np.zeros(X.shape[1])
self.hb = layer.b
self._dW = np.zeros_like(self.W)
self._dvb = np.zeros_like(self.vb)
self._dhb = np.zeros_like(self.hb)
self._rng = RNG(self.random_seed)
self._rng.reseed()
timer = Stopwatch(verbose=False).start()
for _ in xrange(self.n_epochs):
self.epoch += 1
if self.verbose:
print_inline('Epoch {0:>{1}}/{2} '.format(
self.epoch, len(str(self.n_epochs)), self.n_epochs))
if isinstance(self.learning_rate, str):
S, F = map(float, self.learning_rate.split('->'))
self._learning_rate = S + (F - S) * (
1. - np.exp(-(self.epoch - 1.) / 8.)) / (
1. - np.exp(-(self.n_epochs - 1.) / 8.))
else:
self._learning_rate = self.learning_rate
if isinstance(self.momentum, str):
S, F = map(float, self.momentum.split('->'))
self._momentum = S + (F - S) * (
1. - np.exp(-(self.epoch - 1) / 4.)) / (
1. - np.exp(-(self.n_epochs - 1) / 4.))
else:
self._momentum = self.momentum
mean_recon = self.train_epoch(X)
if mean_recon < self.best_recon:
self.best_recon = mean_recon
self.best_epoch = self.epoch
self.best_W = self.W.copy()
self.best_vb = self.vb.copy()
self.best_hb = self.hb.copy()
self._early_stopping = self.early_stopping
msg = 'elapsed: {0} sec'.format(
width_format(timer.elapsed(), default_width=5,
max_precision=2))
msg += ' - recon. mse: {0}'.format(
width_format(mean_recon, default_width=6, max_precision=4))
msg += ' - best r-mse: {0}'.format(
width_format(self.best_recon, default_width=6,
max_precision=4))
if self.early_stopping:
msg += ' {0}*'.format(self._early_stopping)
if self.verbose:
print msg
if self._early_stopping == 0:
return
if self.early_stopping:
self._early_stopping -= 1
def _serialize(self, params):
for attr in ('W', 'best_W', 'vb', 'best_vb', 'hb', 'best_hb'):
if attr in params and params[attr] is not None:
params[attr] = params[attr].tolist()
return params
def _deserialize(self, params):
for attr in ('W', 'best_W', 'vb', 'best_vb', 'hb', 'best_hb'):
if attr in params and params[attr] is not None:
params[attr] = np.asarray(params[attr])
return params