def computation(state, seed):
bijector = tfp.bijectors.Softplus()
base_dist = tfp.distributions.MultivariateNormalFullCovariance(
loc=base_mean, covariance_matrix=base_cov)
target_dist = bijector(base_dist)
def orig_target_log_prob_fn(x):
return target_dist.log_prob(x), ()
target_log_prob_fn, state = fun_mcmc.transform_log_prob_fn(
orig_target_log_prob_fn, bijector, state)
def kernel(hmc_state, step_size_state, step, seed):
if not self._is_on_jax:
hmc_seed = _test_seed()
else:
hmc_seed, seed = util.split_seed(seed, 2)
hmc_state, hmc_extra = fun_mcmc.hamiltonian_monte_carlo(
hmc_state,
step_size=tf.exp(step_size_state.state),
num_integrator_steps=num_leapfrog_steps,
target_log_prob_fn=target_log_prob_fn,
seed=hmc_seed)
rate = fun_mcmc.prefab._polynomial_decay( # pylint: disable=protected-access
step=step,
step_size=self._constant(0.01),
power=0.5,
decay_steps=num_adapt_steps,
final_step_size=0.)
mean_p_accept = tf.reduce_mean(
tf.exp(tf.minimum(self._constant(0.), hmc_extra.log_accept_ratio)))
loss_fn = fun_mcmc.make_surrogate_loss_fn(
lambda _: (0.9 - mean_p_accept, ()))
step_size_state, _ = fun_mcmc.adam_step(
step_size_state, loss_fn, learning_rate=rate)
return ((hmc_state, step_size_state, step + 1, seed),
(hmc_state.state_extra[0], hmc_extra.log_accept_ratio))
_, (chain, log_accept_ratio_trace) = fun_mcmc.trace(
state=(fun_mcmc.hamiltonian_monte_carlo_init(state,
target_log_prob_fn),
fun_mcmc.adam_init(tf.math.log(step_size)), 0, seed),
fn=kernel,
num_steps=num_adapt_steps + num_steps,
)
true_samples = target_dist.sample(
4096, seed=self._make_seed(_test_seed()))
return chain, log_accept_ratio_trace, true_samples
def testAdam(self):
def loss_fn(x, y):
return tf.square(x - 1.) + tf.square(y - 2.), []
_, [(x, y), loss] = fun_mcmc.trace(
fun_mcmc.adam_init([tf.zeros([]), tf.zeros([])]),
lambda adam_state: fun_mcmc.adam_step( # pylint: disable=g-long-lambda
adam_state, loss_fn, learning_rate=0.01),
num_steps=1000,
trace_fn=lambda state, extra: [state.state, extra.loss])
self.assertAllClose(1., x[-1], atol=1e-3)
self.assertAllClose(2., y[-1], atol=1e-3)
self.assertAllClose(0., loss[-1], atol=1e-3)
def computation(state):
bijector = tfb.Softplus()
base_dist = tfd.MultivariateNormalFullCovariance(
loc=base_mean, covariance_matrix=base_cov)
target_dist = bijector(base_dist)
def orig_target_log_prob_fn(x):
return target_dist.log_prob(x), ()
target_log_prob_fn, state = fun_mcmc.transform_log_prob_fn(
orig_target_log_prob_fn, bijector, state)
def kernel(hmc_state, step_size_state, step):
hmc_state, hmc_extra = fun_mcmc.hamiltonian_monte_carlo(
hmc_state,
step_size=tf.exp(step_size_state.state),
num_integrator_steps=num_leapfrog_steps,
target_log_prob_fn=target_log_prob_fn)
rate = tf.compat.v1.train.polynomial_decay(
0.01,
global_step=step,
power=0.5,
decay_steps=num_adapt_steps,
end_learning_rate=0.)
mean_p_accept = tf.reduce_mean(
tf.exp(tf.minimum(0., hmc_extra.log_accept_ratio)))
loss_fn = fun_mcmc.make_surrogate_loss_fn(
lambda _: (0.9 - mean_p_accept, ()))
step_size_state, _ = fun_mcmc.adam_step(
step_size_state, loss_fn, learning_rate=rate)
return ((hmc_state, step_size_state, step + 1),
(hmc_state.state_extra[0], hmc_extra.log_accept_ratio))
_, (chain, log_accept_ratio_trace) = fun_mcmc.trace(
state=(fun_mcmc.hamiltonian_monte_carlo_init(state,
target_log_prob_fn),
fun_mcmc.adam_init(tf.math.log(step_size)), 0),
fn=kernel,
num_steps=num_adapt_steps + num_steps,
)
true_samples = target_dist.sample(4096, seed=_test_seed())
return chain, log_accept_ratio_trace, true_samples
