# 学習可能な分布動物園

このコラボでは、学習可能な（「訓練可能な」）分布を構築するさまざまな例を示します。 （ディストリビューションを説明する努力はせず、それらを構築する方法を示すだけです。）

``````import numpy as np
import tensorflow.compat.v2 as tf
import tensorflow_probability as tfp
from tensorflow_probability.python.internal import prefer_static
tfb = tfp.bijectors
tfd = tfp.distributions
tf.enable_v2_behavior()
``````
``````event_size = 4
num_components = 3
``````

## `chol(Cov)`スケーリングされたアイデンティティを持つ学習可能な多変量正規

``````learnable_mvn_scaled_identity = tfd.Independent(
tfd.Normal(
loc=tf.Variable(tf.zeros(event_size), name='loc'),
scale=tfp.util.TransformedVariable(
tf.ones([event_size, 1]),
bijector=tfb.Exp()),
name='scale'),
reinterpreted_batch_ndims=1,
name='learnable_mvn_scaled_identity')

print(learnable_mvn_scaled_identity)
print(learnable_mvn_scaled_identity.trainable_variables)
``````
```tfp.distributions.Independent("learnable_mvn_scaled_identity", batch_shape=[4], event_shape=[4], dtype=float32)
(<tf.Variable 'Variable:0' shape=(4,) dtype=float32, numpy=array([0., 0., 0., 0.], dtype=float32)>, <tf.Variable 'Variable:0' shape=(4, 1) dtype=float32, numpy=
array([[0.],
[0.],
[0.],
[0.]], dtype=float32)>)
```

## `chol(Cov)`対角を持つ学習可能な多変量正規

``````learnable_mvndiag = tfd.Independent(
tfd.Normal(
loc=tf.Variable(tf.zeros(event_size), name='loc'),
scale=tfp.util.TransformedVariable(
tf.ones(event_size),
bijector=tfb.Softplus()),  # Use Softplus...cuz why not?
name='scale'),
reinterpreted_batch_ndims=1,
name='learnable_mvn_diag')

print(learnable_mvndiag)
print(learnable_mvndiag.trainable_variables)
``````
```tfp.distributions.Independent("learnable_mvn_diag", batch_shape=[], event_shape=[4], dtype=float32)
(<tf.Variable 'Variable:0' shape=(4,) dtype=float32, numpy=array([0., 0., 0., 0.], dtype=float32)>, <tf.Variable 'Variable:0' shape=(4,) dtype=float32, numpy=array([0., 0., 0., 0.], dtype=float32)>)
```

## 多変量法線（球形）の混合物

``````learnable_mix_mvn_scaled_identity = tfd.MixtureSameFamily(
mixture_distribution=tfd.Categorical(
logits=tf.Variable(
# Changing the `1.` intializes with a geometric decay.
-tf.math.log(1.) * tf.range(num_components, dtype=tf.float32),
name='logits')),
components_distribution=tfd.Independent(
tfd.Normal(
loc=tf.Variable(
tf.random.normal([num_components, event_size]),
name='loc'),
scale=tfp.util.TransformedVariable(
10. * tf.ones([num_components, 1]),
bijector=tfb.Softplus()),  # Use Softplus...cuz why not?
name='scale'),
reinterpreted_batch_ndims=1),
name='learnable_mix_mvn_scaled_identity')

print(learnable_mix_mvn_scaled_identity)
print(learnable_mix_mvn_scaled_identity.trainable_variables)
``````
```tfp.distributions.MixtureSameFamily("learnable_mix_mvn_scaled_identity", batch_shape=[], event_shape=[4], dtype=float32)
(<tf.Variable 'Variable:0' shape=(3, 4) dtype=float32, numpy=
array([[-0.11800266, -1.3127382 , -0.1813932 ,  0.24975719],
[ 0.97209346, -0.91694   ,  0.84734786, -1.3201759 ],
[ 0.15194772,  0.33787215, -0.4269769 , -0.26286215]],
dtype=float32)>, <tf.Variable 'Variable:0' shape=(3, 1) dtype=float32, numpy=
array([[-4.600166],
[-4.600166],
[-4.600166]], dtype=float32)>, <tf.Variable 'logits:0' shape=(3,) dtype=float32, numpy=array([-0., -0., -0.], dtype=float32)>)
```

## 多変量正規（球形）と最初の混合重みの混合は学習できません

``````learnable_mix_mvndiag_first_fixed = tfd.MixtureSameFamily(
mixture_distribution=tfd.Categorical(
logits=tfp.util.TransformedVariable(
# Initialize logits as geometric decay.
-tf.math.log(1.5) * tf.range(num_components, dtype=tf.float32),
name='logits'),
components_distribution=tfd.Independent(
tfd.Normal(
loc=tf.Variable(
name='loc'),
scale=tfp.util.TransformedVariable(
10. * tf.ones([num_components, 1]),
bijector=tfb.Softplus()),  # Use Softplus...cuz why not?
name='scale'),
reinterpreted_batch_ndims=1),
name='learnable_mix_mvndiag_first_fixed')

print(learnable_mix_mvndiag_first_fixed)
print(learnable_mix_mvndiag_first_fixed.trainable_variables)
``````
```tfp.distributions.MixtureSameFamily("learnable_mix_mvndiag_first_fixed", batch_shape=[], event_shape=[4], dtype=float32)
(<tf.Variable 'Variable:0' shape=(3, 4) dtype=float32, numpy=
array([[-1., -1.,  1., -1.],
[-1., -1., -1., -1.],
[ 1.,  1.,  1., -1.]], dtype=float32)>, <tf.Variable 'Variable:0' shape=(3, 4) dtype=float32, numpy=
array([[-4.600166, -4.600166, -4.600166, -4.600166],
[-4.600166, -4.600166, -4.600166, -4.600166],
[-4.600166, -4.600166, -4.600166, -4.600166]], dtype=float32)>, <tf.Variable 'Variable:0' shape=(2,) dtype=float32, numpy=array([-0.4054651, -0.8109302], dtype=float32)>)
```

## 多変量正規`Cov`混合（完全な`Cov` ）

``````learnable_mix_mvntril = tfd.MixtureSameFamily(
mixture_distribution=tfd.Categorical(
logits=tf.Variable(
# Changing the `1.` intializes with a geometric decay.
-tf.math.log(1.) * tf.range(num_components, dtype=tf.float32),
name='logits')),
components_distribution=tfd.MultivariateNormalTriL(
loc=tf.Variable(tf.zeros([num_components, event_size]), name='loc'),
scale_tril=tfp.util.TransformedVariable(
10. * tf.eye(event_size, batch_shape=[num_components]),
bijector=tfb.FillScaleTriL()),
name='scale_tril'),
name='learnable_mix_mvntril')

print(learnable_mix_mvntril)
print(learnable_mix_mvntril.trainable_variables)
``````
```tfp.distributions.MixtureSameFamily("learnable_mix_mvntril", batch_shape=[], event_shape=[4], dtype=float32)
(<tf.Variable 'Variable:0' shape=(3, 4) dtype=float32, numpy=
array([[ 1.4036556 , -0.22486973,  0.8365339 ,  1.1744921 ],
[-0.14385273,  1.5095806 ,  0.78327304, -0.64133334],
[-0.22640549,  1.908316  ,  1.1216396 , -1.2109828 ]],
dtype=float32)>, <tf.Variable 'Variable:0' shape=(3, 10) dtype=float32, numpy=
array([[-4.6011715,  0.       ,  0.       ,  0.       , -4.6011715,
-4.6011715,  0.       ,  0.       ,  0.       , -4.6011715],
[-4.6011715,  0.       ,  0.       ,  0.       , -4.6011715,
-4.6011715,  0.       ,  0.       ,  0.       , -4.6011715],
[-4.6011715,  0.       ,  0.       ,  0.       , -4.6011715,
-4.6011715,  0.       ,  0.       ,  0.       , -4.6011715]],
dtype=float32)>, <tf.Variable 'logits:0' shape=(3,) dtype=float32, numpy=array([-0., -0., -0.], dtype=float32)>)
```

## 多変量正規（フル`Cov` ）と学習不可能な最初の混合および最初のコンポーネントの混合

``````# Make a bijector which pads an eye to what otherwise fills a tril.
num_tril_nonzero = lambda num_rows: num_rows * (num_rows + 1) // 2

num_tril_rows = lambda nnz: prefer_static.cast(
prefer_static.sqrt(0.25 + 2. * prefer_static.cast(nnz, tf.float32)) - 0.5,
tf.int32)

# TFP doesn't have a concat bijector, so we roll out our own.

def __init__(self, tril_fn=None):
if tril_fn is None:
tril_fn = tfb.FillScaleTriL()
self._tril_fn = getattr(tril_fn, 'inverse', tril_fn)
forward_min_event_ndims=2,
inverse_min_event_ndims=2,
is_constant_jacobian=True,

def _forward(self, x):
num_rows = int(num_tril_rows(tf.compat.dimension_value(x.shape[-1])))
eye = tf.eye(num_rows, batch_shape=prefer_static.shape(x)[:-2])
return tf.concat([self._tril_fn(eye)[..., tf.newaxis, :], x],
axis=prefer_static.rank(x) - 2)

def _inverse(self, y):
return y[..., 1:, :]

def _forward_log_det_jacobian(self, x):
return tf.zeros([], dtype=x.dtype)

def _inverse_log_det_jacobian(self, y):
return tf.zeros([], dtype=y.dtype)

def _forward_event_shape(self, in_shape):
n = prefer_static.size(in_shape)
return in_shape + prefer_static.one_hot(n - 2, depth=n, dtype=tf.int32)

def _inverse_event_shape(self, out_shape):
n = prefer_static.size(out_shape)
return out_shape - prefer_static.one_hot(n - 2, depth=n, dtype=tf.int32)

tril_bijector = tfb.FillScaleTriL(diag_bijector=tfb.Softplus())
learnable_mix_mvntril_fixed_first = tfd.MixtureSameFamily(
mixture_distribution=tfd.Categorical(
logits=tfp.util.TransformedVariable(
# Changing the `1.` intializes with a geometric decay.
-tf.math.log(1.) * tf.range(num_components, dtype=tf.float32),
name='logits')),
components_distribution=tfd.MultivariateNormalTriL(
loc=tfp.util.TransformedVariable(
tf.zeros([num_components, event_size]),
name='loc'),
scale_tril=tfp.util.TransformedVariable(
10. * tf.eye(event_size, batch_shape=[num_components]),
name='scale_tril')),
name='learnable_mix_mvntril_fixed_first')

print(learnable_mix_mvntril_fixed_first)
print(learnable_mix_mvntril_fixed_first.trainable_variables)
``````
```tfp.distributions.MixtureSameFamily("learnable_mix_mvntril_fixed_first", batch_shape=[], event_shape=[4], dtype=float32)
(<tf.Variable 'loc:0' shape=(2, 4) dtype=float32, numpy=
array([[ 0.53900903, -0.17989647, -1.196744  , -1.0601326 ],
[ 0.46199334,  1.2968503 ,  0.20908853, -0.36455044]],
dtype=float32)>, <tf.Variable 'Variable:0' shape=(2, 10) dtype=float32, numpy=
array([[-4.6011715,  0.       ,  0.       ,  0.       , -4.6011715,
-4.6011715,  0.       ,  0.       ,  0.       , -4.6011715],
[-4.6011715,  0.       ,  0.       ,  0.       , -4.6011715,
-4.6011715,  0.       ,  0.       ,  0.       , -4.6011715]],
dtype=float32)>, <tf.Variable 'logits:0' shape=(2,) dtype=float32, numpy=array([-0., -0.], dtype=float32)>)
```
[{ "type": "thumb-down", "id": "missingTheInformationINeed", "label":"必要な情報がない" },{ "type": "thumb-down", "id": "tooComplicatedTooManySteps", "label":"複雑すぎる / 手順が多すぎる" },{ "type": "thumb-down", "id": "outOfDate", "label":"最新ではない" },{ "type": "thumb-down", "id": "translationIssue", "label":"翻訳に関する問題" },{ "type": "thumb-down", "id": "samplesCodeIssue", "label":"Samples / code issue" },{ "type": "thumb-down", "id": "otherDown", "label":"その他" }]
[{ "type": "thumb-up", "id": "easyToUnderstand", "label":"わかりやすい" },{ "type": "thumb-up", "id": "solvedMyProblem", "label":"問題の解決に役立った" },{ "type": "thumb-up", "id": "otherUp", "label":"その他" }]