如何解决如何将 tfp.density.Mixture 与 JointDistributionCoroutine 一起使用
我正在尝试为 MCMC 定义模型函数。 这个想法是将两种分布混合在一起,并以概率比进行控制。 我的尝试之一如下所示:
import tensorflow as tf
import tensorflow_probability as tfp
tfd = tfp.distributions
root = tfd.JointDistributionCoroutine.Root
def model_fn():
rv_p = yield root(tfd.Sample(tfd.Uniform(0.0,1.0),1))
catprobs = tf.stack([rv_p,1.-rv_p],0)
rv_cat = tfd.Categorical(probs=catprobs)
rv_norm1 = tfd.Sample(tfd.Normal(0.0,1)
rv_norm2 = tfd.Sample(tfd.Normal(3.0,1)
rv_mix = yield tfd.Mixture(cat=rv_cat,components=[
rv_norm1,rv_norm2,])
jd = tfd.JointDistributionCoroutine(model_fn)
jd.sample(2)
代码失败:
ValueError: components[0] batch shape must be compatible with cat shape and other component batch shapes ((2,2) vs ())
您能否举一个例子来说明如何以允许“任何”输入形状的方式使用 Mixture 分布?
我在 python 3.6 中使用 tensorflow 2.4.1 和 tensorflow_probability 0.12.1
解决方法
我想通了。这里有一个示例代码供参考:
import os
os.environ['CUDA_VISIBLE_DEVICES'] = '-1'
import tensorflow as tf
import tensorflow_probability as tfp
import matplotlib.pyplot as plt
tfd = tfp.distributions
tfb = tfp.bijectors
import numpy as np
from time import time
numdata = 10000
data = np.random.normal(0.0,1.0,numdata).astype(np.float32)
data[int(numdata/2):] = 0.0
_=plt.hist(data,30,density=True)
root = tfd.JointDistributionCoroutine.Root
def dist_fn(rv_p,rv_mu):
rv_cat = tfd.Categorical(probs=tf.stack([rv_p,1.-rv_p],-1))
rv_norm = tfd.Normal(rv_mu,1.0)
rv_zero = tfd.Deterministic(tf.zeros_like(rv_mu))
rv_mix = tfd.Independent(
tfd.Mixture(cat=rv_cat,components=[rv_norm,rv_zero]),reinterpreted_batch_ndims=1)
return rv_mix
def model_fn():
rv_p = yield root(tfd.Sample(tfd.Uniform(0.0,1.0),1))
rv_mu = yield root(tfd.Sample(tfd.Uniform(-1.,1. ),1))
rv_mix = yield dist_fn(rv_p,rv_mu)
jd = tfd.JointDistributionCoroutine(model_fn)
unnormalized_posterior_log_prob = lambda *args: jd.log_prob(args + (data,))
n_chains = 1
p_init = [0.3]
p_init = tf.cast(p_init,dtype=tf.float32)
mu_init = 0.1
mu_init = tf.stack([mu_init]*n_chains,axis=0)
initial_chain_state = [
p_init,mu_init,]
bijectors = [
tfb.Sigmoid(),# p
tfb.Identity(),# mu
]
step_size = 0.01
num_results = 50000
num_burnin_steps = 50000
kernel=tfp.mcmc.TransformedTransitionKernel(
inner_kernel=tfp.mcmc.HamiltonianMonteCarlo(
target_log_prob_fn=unnormalized_posterior_log_prob,num_leapfrog_steps=2,step_size=step_size,state_gradients_are_stopped=True),bijector=bijectors)
kernel = tfp.mcmc.SimpleStepSizeAdaptation(
inner_kernel=kernel,num_adaptation_steps=int(num_burnin_steps * 0.8))
#XLA optim
@tf.function(autograph=False,experimental_compile=True)
def graph_sample_chain(*args,**kwargs):
return tfp.mcmc.sample_chain(*args,**kwargs)
st = time()
trace,stats = graph_sample_chain(
num_results=num_results,num_burnin_steps=num_burnin_steps,current_state=initial_chain_state,kernel=kernel)
et = time()
print(et-st)
ptrace,mutrace = trace
plt.subplot(121)
_=plt.hist(ptrace.numpy(),100,density=True)
plt.subplot(122)
_=plt.hist(mutrace.numpy(),density=True)
print(np.mean(ptrace),np.mean(mutrace))
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