def compute_one_hot_reconstructions(rbm, fit, level, n_recon, num_to_avg=1):
n = rbm.layers[level].len
grid_size = int(sqrt(n_recon))
one_hotz = rbm.layers[level].onehot(n)
v_model = be.zeros((n, rbm.layers[0].len))
for k in range(num_to_avg):
# set up the initial state
state = State.from_model(n, rbm)
state.units[level] = one_hotz
dropout_scale = State.dropout_rescale(rbm)
# set up a sampler and update the state
reconstructions = fit.SequentialMC(rbm,
clamped=[level],
updater='mean_field_iteration')
reconstructions.set_state(state)
reconstructions.update_state(10, dropout_scale)
v_model += reconstructions.state.units[0]
v_model /= num_to_avg
# plot the resulting visible unit activations
idx = numpy.random.choice(range(len(v_model)), n_recon, replace=False)
recons = numpy.array([be.to_numpy_array(v_model[i]) for i in idx])
recons = recons.reshape(grid_size, grid_size, -1)
return recons
def test_conditional_sampling():
"""
Test sampling from one layer conditioned on the state of another layer.
Note:
This test compares values estimated by *sampling* to values computed
analytically. It can fail for small batch_size, or strict tolerances,
even if everything is working propery.
"""
num_visible_units = 20
num_hidden_units = 10
steps = 1000
mean_tol = 0.1
# set a seed for the random number generator
be.set_seed()
layer_types = [layers.BernoulliLayer, layers.GaussianLayer]
for layer_type in layer_types:
# set up some layer and model objects
vis_layer = layer_type(num_visible_units)
hid_layer = layer_type(num_hidden_units)
rbm = model.Model([vis_layer, hid_layer])
# randomly set the intrinsic model parameters
a = be.rand((num_visible_units, ))
b = be.rand((num_hidden_units, ))
W = 10 * be.rand((num_visible_units, num_hidden_units))
rbm.layers[0].params.loc[:] = a
rbm.layers[1].params.loc[:] = b
rbm.weights[0].params.matrix[:] = W
if layer_type == layers.GaussianLayer:
log_var_a = be.randn((num_visible_units, ))
log_var_b = be.randn((num_hidden_units, ))
rbm.layers[0].params.log_var[:] = log_var_a
rbm.layers[1].params.log_var[:] = log_var_b
# initialize a state
state = State.from_model(1, rbm)
dropout = State.dropout_rescale(rbm)
# set up a calculator for the moments
moments = mu.MeanVarianceArrayCalculator()
for _ in range(steps):
moments.update(rbm.layers[0].conditional_sample(
rbm._connected_rescaled_units(0, state, dropout),
rbm._connected_weights(0)))
model_mean = rbm.layers[0].conditional_mean(
rbm._connected_rescaled_units(0, state, dropout),
rbm._connected_weights(0))
ave = moments.mean
close = be.allclose(ave, model_mean[0], rtol=mean_tol, atol=mean_tol)
assert close, "{} conditional mean".format(layer_type)
if layer_type == layers.GaussianLayer:
model_mean, model_var = rbm.layers[0]._conditional_params(
rbm._connected_rescaled_units(0, state, dropout),
rbm._connected_weights(0))
close = be.allclose(be.sqrt(moments.var),
be.sqrt(model_var[0]),
rtol=mean_tol,
atol=mean_tol)
assert close, "{} conditional standard deviation".format(
layer_type)
def test_independent():
"""
Test sampling from an rbm with two layers connected by a weight matrix that
contains all zeros, so that the layers are independent.
Note:
This test compares values estimated by *sampling* to values computed
analytically. It can fail for small batch_size, or strict tolerances,
even if everything is working propery.
"""
num_visible_units = 20
num_hidden_units = 10
batch_size = 1000
steps = 100
mean_tol = 0.1
corr_tol = 0.2
# set a seed for the random number generator
be.set_seed()
layer_types = [layers.BernoulliLayer, layers.GaussianLayer]
for layer_type in layer_types:
# set up some layer and model objects
vis_layer = layer_type(num_visible_units)
hid_layer = layer_type(num_hidden_units)
rbm = model.Model([vis_layer, hid_layer])
# randomly set the intrinsic model parameters
a = be.rand((num_visible_units, ))
b = be.rand((num_hidden_units, ))
W = be.zeros((num_visible_units, num_hidden_units))
rbm.layers[0].params.loc[:] = a
rbm.layers[1].params.loc[:] = b
rbm.weights[0].params.matrix[:] = W
if layer_type == layers.GaussianLayer:
log_var_a = be.randn((num_visible_units, ))
log_var_b = be.randn((num_hidden_units, ))
rbm.layers[0].params.log_var[:] = log_var_a
rbm.layers[1].params.log_var[:] = log_var_b
# initialize a state
state = State.from_model(batch_size, rbm)
dropout = State.dropout_rescale(rbm)
# run a markov chain to update the state
state = rbm.markov_chain(steps, state, dropout)
# compute the mean
state_for_moments = State.from_model(1, rbm)
sample_mean = [
be.mean(state.units[i], axis=0) for i in range(len(state.units))
]
model_mean = [
rbm.layers[i].conditional_mean(
rbm._connected_rescaled_units(i, state_for_moments, dropout),
rbm._connected_weights(i)) for i in range(rbm.num_layers)
]
# check that the means are roughly equal
for i in range(rbm.num_layers):
ave = sample_mean[i]
close = be.allclose(ave,
model_mean[i][0],
rtol=mean_tol,
atol=mean_tol)
assert close, "{0} {1}: sample mean does not match model mean".format(
layer_type, i)
# check the cross correlation between the layers
crosscov = be.cov(state.units[0], state.units[1])
norm = be.outer(be.std(state.units[0], axis=0),
be.std(state.units[1], axis=0))
crosscorr = be.divide(norm, crosscov)
assert be.tmax(
be.tabs(crosscorr)
) < corr_tol, "{} cross correlation too large".format(layer_type)