def _mean(self):
with ops.control_dependencies(self._runtime_assertions):
probs = distribution_utils.pad_mixture_dimensions(
self.mixture_distribution.probs, self,
self.mixture_distribution,
self._event_shape().ndims) # [B, k, [1]*e]
return math_ops.reduce_sum(probs *
self.components_distribution.mean(),
axis=-1 - self._event_ndims) # [B, E]
def test_pad_mixture_dimensions_mixture_same_family(self):
with self.cached_session() as sess:
gm = mixture_same_family.MixtureSameFamily(
mixture_distribution=categorical.Categorical(probs=[0.3, 0.7]),
components_distribution=mvn_diag.MultivariateNormalDiag(
loc=[[-1., 1], [1, -1]],
scale_identity_multiplier=[1.0, 0.5]))
x = array_ops.constant([[1.0, 2.0], [3.0, 4.0]])
x_pad = distribution_util.pad_mixture_dimensions(
x, gm, gm.mixture_distribution, gm.event_shape.ndims)
x_out, x_pad_out = sess.run([x, x_pad])
self.assertAllEqual(x_pad_out.shape, [2, 2, 1])
self.assertAllEqual(x_out.reshape([-1]), x_pad_out.reshape([-1]))
def _covariance(self):
static_event_ndims = self.event_shape.ndims
if static_event_ndims != 1:
# Covariance is defined only for vector distributions.
raise NotImplementedError("covariance is not implemented")
with ops.control_dependencies(self._runtime_assertions):
# Law of total variance: Var(Y) = E[Var(Y|X)] + Var(E[Y|X])
probs = distribution_utils.pad_mixture_dimensions(
distribution_utils.pad_mixture_dimensions(
self.mixture_distribution.probs, self,
self.mixture_distribution,
self._event_shape().ndims), self,
self.mixture_distribution,
self._event_shape().ndims) # [B, k, 1, 1]
mean_cond_var = math_ops.reduce_sum(
probs * self.components_distribution.covariance(),
axis=-3) # [B, e, e]
var_cond_mean = math_ops.reduce_sum(
probs *
_outer_squared_difference(self.components_distribution.mean(),
self._pad_sample_dims(self._mean())),
axis=-3) # [B, e, e]
return mean_cond_var + var_cond_mean # [B, e, e]
def _sample_n(self, n, seed):
with ops.control_dependencies(self._runtime_assertions):
x = self.components_distribution.sample(n) # [n, B, k, E]
# TODO(jvdillon): Consider using tf.gather (by way of index unrolling).
npdt = x.dtype.as_numpy_dtype
mask = array_ops.one_hot(
indices=self.mixture_distribution.sample(n), # [n, B]
depth=self._num_components, # == k
on_value=np.ones([], dtype=npdt),
off_value=np.zeros([], dtype=npdt)) # [n, B, k]
mask = distribution_utils.pad_mixture_dimensions(
mask, self, self.mixture_distribution,
self._event_shape().ndims) # [n, B, k, [1]*e]
return math_ops.reduce_sum(x * mask, axis=-1 -
self._event_ndims) # [n, B, E]
def test_pad_mixture_dimensions_mixture(self):
with self.cached_session() as sess:
gm = mixture.Mixture(
cat=categorical.Categorical(probs=[[0.3, 0.7]]),
components=[
normal.Normal(loc=[-1.0], scale=[1.0]),
normal.Normal(loc=[1.0], scale=[0.5])
])
x = array_ops.constant([[1.0, 2.0], [3.0, 4.0]])
x_pad = distribution_util.pad_mixture_dimensions(
x, gm, gm.cat, gm.event_shape.ndims)
x_out, x_pad_out = sess.run([x, x_pad])
self.assertAllEqual(x_pad_out.shape, [2, 2])
self.assertAllEqual(x_out.reshape([-1]), x_pad_out.reshape([-1]))
def _variance(self):
with ops.control_dependencies(self._runtime_assertions):
# Law of total variance: Var(Y) = E[Var(Y|X)] + Var(E[Y|X])
probs = distribution_utils.pad_mixture_dimensions(
self.mixture_distribution.probs, self,
self.mixture_distribution,
self._event_shape().ndims) # [B, k, [1]*e]
mean_cond_var = math_ops.reduce_sum(
probs * self.components_distribution.variance(),
axis=-1 - self._event_ndims) # [B, E]
var_cond_mean = math_ops.reduce_sum(
probs * math_ops.squared_difference(
self.components_distribution.mean(),
self._pad_sample_dims(self._mean())),
axis=-1 - self._event_ndims) # [B, E]
return mean_cond_var + var_cond_mean # [B, E]
def _sample_n(self, n, seed=None):
if self._use_static_graph:
# This sampling approach is almost the same as the approach used by
# `MixtureSameFamily`. The differences are due to having a list of
# `Distribution` objects rather than a single object, and maintaining
# random seed management that is consistent with the non-static code path.
samples = []
cat_samples = self.cat.sample(n, seed=seed)
for c in range(self.num_components):
seed = distribution_util.gen_new_seed(seed, "mixture")
samples.append(self.components[c].sample(n, seed=seed))
x = array_ops.stack(samples, -self._static_event_shape.ndims -
1) # [n, B, k, E]
npdt = x.dtype.as_numpy_dtype
mask = array_ops.one_hot(
indices=cat_samples, # [n, B]
depth=self._num_components, # == k
on_value=np.ones([], dtype=npdt),
off_value=np.zeros([], dtype=npdt)) # [n, B, k]
mask = distribution_utils.pad_mixture_dimensions(
mask, self, self._cat,
self._static_event_shape.ndims) # [n, B, k, [1]*e]
return math_ops.reduce_sum(
x * mask,
axis=-1 - self._static_event_shape.ndims) # [n, B, E]
with ops.control_dependencies(self._assertions):
n = ops.convert_to_tensor(n, name="n")
static_n = tensor_util.constant_value(n)
n = int(static_n) if static_n is not None else n
cat_samples = self.cat.sample(n, seed=seed)
static_samples_shape = cat_samples.get_shape()
if static_samples_shape.is_fully_defined():
samples_shape = static_samples_shape.as_list()
samples_size = static_samples_shape.num_elements()
else:
samples_shape = array_ops.shape(cat_samples)
samples_size = array_ops.size(cat_samples)
static_batch_shape = self.batch_shape
if static_batch_shape.is_fully_defined():
batch_shape = static_batch_shape.as_list()
batch_size = static_batch_shape.num_elements()
else:
batch_shape = self.batch_shape_tensor()
batch_size = math_ops.reduce_prod(batch_shape)
static_event_shape = self.event_shape
if static_event_shape.is_fully_defined():
event_shape = np.array(static_event_shape.as_list(),
dtype=np.int32)
else:
event_shape = self.event_shape_tensor()
# Get indices into the raw cat sampling tensor. We will
# need these to stitch sample values back out after sampling
# within the component partitions.
samples_raw_indices = array_ops.reshape(
math_ops.range(0, samples_size), samples_shape)
# Partition the raw indices so that we can use
# dynamic_stitch later to reconstruct the samples from the
# known partitions.
partitioned_samples_indices = data_flow_ops.dynamic_partition(
data=samples_raw_indices,
partitions=cat_samples,
num_partitions=self.num_components)
# Copy the batch indices n times, as we will need to know
# these to pull out the appropriate rows within the
# component partitions.
batch_raw_indices = array_ops.reshape(
array_ops.tile(math_ops.range(0, batch_size), [n]),
samples_shape)
# Explanation of the dynamic partitioning below:
# batch indices are i.e., [0, 1, 0, 1, 0, 1]
# Suppose partitions are:
# [1 1 0 0 1 1]
# After partitioning, batch indices are cut as:
# [batch_indices[x] for x in 2, 3]
# [batch_indices[x] for x in 0, 1, 4, 5]
# i.e.
# [1 1] and [0 0 0 0]
# Now we sample n=2 from part 0 and n=4 from part 1.
# For part 0 we want samples from batch entries 1, 1 (samples 0, 1),
# and for part 1 we want samples from batch entries 0, 0, 0, 0
# (samples 0, 1, 2, 3).
partitioned_batch_indices = data_flow_ops.dynamic_partition(
data=batch_raw_indices,
partitions=cat_samples,
num_partitions=self.num_components)
samples_class = [None for _ in range(self.num_components)]
for c in range(self.num_components):
n_class = array_ops.size(partitioned_samples_indices[c])
seed = distribution_util.gen_new_seed(seed, "mixture")
samples_class_c = self.components[c].sample(n_class, seed=seed)
# Pull out the correct batch entries from each index.
# To do this, we may have to flatten the batch shape.
# For sample s, batch element b of component c, we get the
# partitioned batch indices from
# partitioned_batch_indices[c]; and shift each element by
# the sample index. The final lookup can be thought of as
# a matrix gather along locations (s, b) in
# samples_class_c where the n_class rows correspond to
# samples within this component and the batch_size columns
# correspond to batch elements within the component.
#
# Thus the lookup index is
# lookup[c, i] = batch_size * s[i] + b[c, i]
# for i = 0 ... n_class[c] - 1.
lookup_partitioned_batch_indices = (
batch_size * math_ops.range(n_class) +
partitioned_batch_indices[c])
samples_class_c = array_ops.reshape(
samples_class_c,
array_ops.concat([[n_class * batch_size], event_shape], 0))
samples_class_c = array_ops.gather(
samples_class_c,
lookup_partitioned_batch_indices,
name="samples_class_c_gather")
samples_class[c] = samples_class_c
# Stitch back together the samples across the components.
lhs_flat_ret = data_flow_ops.dynamic_stitch(
indices=partitioned_samples_indices, data=samples_class)
# Reshape back to proper sample, batch, and event shape.
ret = array_ops.reshape(
lhs_flat_ret,
array_ops.concat(
[samples_shape, self.event_shape_tensor()], 0))
ret.set_shape(
tensor_shape.TensorShape(static_samples_shape).concatenate(
self.event_shape))
return ret