def test_end_to_end_prediction_works_and_is_deterministic(
self, dtype, use_xla, use_spike_and_slab):
if not tf.executing_eagerly():
return
seed = test_util.test_seed(sampler_type='stateless')
model, observed_time_series, is_missing = self._build_test_model(
num_timesteps=5,
batch_shape=[3],
prior_class=gibbs_sampler.XLACompilableInverseGamma,
sparse_weights_nonzero_prob=0.5 if use_spike_and_slab else None,
dtype=dtype)
@tf.function(jit_compile=use_xla)
def do_sampling(observed_time_series, is_missing):
return gibbs_sampler.fit_with_gibbs_sampling(
model, tfp.sts.MaskedTimeSeries(
observed_time_series, is_missing),
num_results=4, num_warmup_steps=1, seed=seed)
samples = do_sampling(observed_time_series[..., tf.newaxis], is_missing)
predictive_dist = gibbs_sampler.one_step_predictive(
model, samples, thin_every=1)
# Test that the seeded calculation gives the same result on multiple runs.
samples2 = do_sampling(observed_time_series[..., tf.newaxis], is_missing)
predictive_dist2 = gibbs_sampler.one_step_predictive(
model, samples2, thin_every=1)
(predictive_mean_, predictive_stddev_,
predictive_mean2_, predictive_stddev2_) = self.evaluate((
predictive_dist.mean(), predictive_dist.stddev(),
predictive_dist2.mean(), predictive_dist2.stddev()))
self.assertAllEqual(predictive_mean_, predictive_mean2_)
self.assertAllEqual(predictive_stddev_, predictive_stddev2_)
def test_forecasts_are_sane(self):
seed = test_util.test_seed()
num_observed_steps = 5
num_forecast_steps = 3
model, observed_time_series, is_missing = self._build_test_model(
num_timesteps=num_observed_steps + num_forecast_steps,
batch_shape=[3])
samples = gibbs_sampler.fit_with_gibbs_sampling(
model,
tfp.sts.MaskedTimeSeries(
observed_time_series[..., :num_observed_steps, tf.newaxis],
is_missing[..., :num_observed_steps]),
num_results=5,
num_warmup_steps=10,
seed=seed,
compile_steps_with_xla=False)
predictive_dist = gibbs_sampler.one_step_predictive(
model,
samples,
num_forecast_steps=num_forecast_steps,
thin_every=1)
predictive_mean, predictive_stddev = self.evaluate(
(predictive_dist.mean(), predictive_dist.stddev()))
self.assertAllEqual(predictive_mean.shape,
[3, num_observed_steps + num_forecast_steps])
self.assertAllEqual(predictive_stddev.shape,
[3, num_observed_steps + num_forecast_steps])
# Uncertainty should increase over the forecast period.
self.assertTrue(
np.all(predictive_stddev[..., num_observed_steps + 1:] >
predictive_stddev[..., num_observed_steps:-1]))
def _detect_anomalies_inner(observed_time_series,
seasonal_structure,
anomaly_threshold=0.01,
num_warmup_steps=50,
num_samples=100,
use_gibbs_predictive_dist=True,
seed=None):
"""Helper function for `detect_anomalies` to cache `tf.function` traces."""
with tf.name_scope('build_default_model_for_gibbs_sampling'):
observed_mean, observed_stddev, _ = sts_util.empirical_statistics(
observed_time_series)
# Center the series to have mean 0 and stddev 1. Alternately, we could
# rescale the priors to match the series, but this is simpler.
observed_mean = observed_mean[...,
tf.newaxis] # Broadcast with num_steps.
observed_stddev = observed_stddev[..., tf.newaxis]
observed_time_series = observed_time_series._replace(
time_series=(observed_time_series.time_series -
observed_mean[..., tf.newaxis]) /
observed_stddev[..., tf.newaxis])
model, posterior_samples = _fit_seasonal_model_with_gibbs_sampling(
observed_time_series,
seasonal_structure=seasonal_structure,
num_results=num_samples,
num_warmup_steps=num_warmup_steps,
seed=seed)
parameter_samples = _parameter_samples_from_gibbs_posterior(
model, posterior_samples)
if use_gibbs_predictive_dist:
predictive_dist = gibbs_sampler.one_step_predictive(
model, posterior_samples)
else:
# Rebuild the model using appropriate Seasonal components, throwing away
# the seasonal effects fit by the Gibbs sampler. Instead, the predictive
# model incorporates the seasonal effects in its state space, so their
# posterior is tracked exactly (rather than by sampling) and is updated
# with each step of the series. This avoids the learning-from-the-future
# behavior of the Gibbs-estimated effects.
seasonal_model = (
model.components[0] + # LocalLinearTrend component.
default_model.model_from_seasonal_structure(
seasonal_structure,
observed_time_series,
# Gibbs sampling didn't fit a drift scale(s).
allow_drift=False))
predictive_dist = one_step_predictive(
seasonal_model,
observed_time_series,
timesteps_are_event_shape=False,
parameter_samples=parameter_samples)
prob_lower = predictive_dist.cdf(observed_time_series.time_series[...,
0])
tail_probabilities = 2 * tf.minimum(prob_lower, 1 - prob_lower)
lower_limit, upper_limit, predictive_mean = compute_predictive_bounds(
predictive_dist, anomaly_threshold=anomaly_threshold)
restore_scale = lambda x: x * observed_stddev + observed_mean
return (restore_scale(lower_limit), restore_scale(upper_limit),
restore_scale(predictive_mean), tail_probabilities)
def test_end_to_end_prediction_works_and_is_deterministic(
self, dtype, use_xla):
if not tf.executing_eagerly():
return
seed = test_util.test_seed()
model, observed_time_series, is_missing = self._build_test_model(
num_timesteps=5, batch_shape=[3])
samples = gibbs_sampler.fit_with_gibbs_sampling(
model,
tfp.sts.MaskedTimeSeries(observed_time_series[..., tf.newaxis],
is_missing),
num_results=4,
num_warmup_steps=1,
seed=seed,
compile_steps_with_xla=use_xla)
predictive_dist = gibbs_sampler.one_step_predictive(model,
samples,
thin_every=1)
# Test that the seeded calculation gives the same result on multiple runs.
samples2 = gibbs_sampler.fit_with_gibbs_sampling(
model,
tfp.sts.MaskedTimeSeries(observed_time_series, is_missing),
num_results=4,
num_warmup_steps=1,
seed=seed,
compile_steps_with_xla=use_xla)
predictive_dist2 = gibbs_sampler.one_step_predictive(model,
samples2,
thin_every=1)
(predictive_mean_, predictive_stddev_, predictive_mean2_,
predictive_stddev2_) = self.evaluate(
(predictive_dist.mean(), predictive_dist.stddev(),
predictive_dist2.mean(), predictive_dist2.stddev()))
self.assertAllEqual(predictive_mean_, predictive_mean2_)
self.assertAllEqual(predictive_stddev_, predictive_stddev2_)
def test_forecasts_match_reference(self,
use_slope,
num_chains,
time_series_shift,
use_zero_step_prediction=False):
seed = test_util.test_seed()
num_observed_steps = 5
num_forecast_steps = 4
num_results = 10000
# Dividing the number of results with number of chains so we sample the same
# total number of MCMC samples.
if not tf.nest.is_nested(num_chains):
num_results = num_results // num_chains
model, observed_time_series, is_missing = self._build_test_model(
num_timesteps=num_observed_steps + num_forecast_steps,
true_slope_scale=0.5 if use_slope else None,
batch_shape=[3],
time_series_shift=time_series_shift)
@tf.function(autograph=False)
def do_sampling():
return gibbs_sampler.fit_with_gibbs_sampling(
model,
tfp.sts.MaskedTimeSeries(
observed_time_series[..., :num_observed_steps, tf.newaxis],
is_missing[..., :num_observed_steps]),
num_chains=num_chains,
num_results=num_results,
num_warmup_steps=100,
seed=seed)
samples = self.evaluate(do_sampling())
def reshape_chain_and_sample(x):
if np.ndim(x) > 2:
return np.reshape(x, [x.shape[0] * x.shape[1], *x.shape[2:]])
return x
if not tf.nest.is_nested(num_chains):
samples = tf.nest.map_structure(reshape_chain_and_sample, samples)
predictive_dist = gibbs_sampler.one_step_predictive(
model,
samples,
num_forecast_steps=num_forecast_steps,
thin_every=1,
use_zero_step_prediction=use_zero_step_prediction)
predictive_mean, predictive_stddev = self.evaluate((
predictive_dist.mean(), predictive_dist.stddev()))
self.assertAllEqual(predictive_mean.shape,
[3, num_observed_steps + num_forecast_steps])
self.assertAllEqual(predictive_stddev.shape,
[3, num_observed_steps + num_forecast_steps])
# big tolerance, but makes sure the predictive mean initializes near
# the initial time series value
self.assertAllClose(tf.reduce_mean(predictive_mean[:, 0]),
observed_time_series[0, 0],
atol=10.)
if use_slope:
parameter_samples = (samples.observation_noise_scale,
samples.level_scale,
samples.slope_scale,
samples.weights)
else:
parameter_samples = (samples.observation_noise_scale,
samples.level_scale,
samples.weights)
# Note that although we expect the Gibbs-sampled forecasts to match a
# reference implementation, we *don't* expect the one-step predictions to
# match `tfp.sts.one_step_predictive`, because that makes predictions using
# a filtered posterior (i.e., given only previous observations) whereas the
# Gibbs-sampled latent `level`s will incorporate some information from
# future observations.
reference_forecast_dist = tfp.sts.forecast(
model,
observed_time_series=observed_time_series[..., :num_observed_steps],
parameter_samples=parameter_samples,
num_steps_forecast=num_forecast_steps)
reference_forecast_mean, reference_forecast_stddev = self.evaluate((
reference_forecast_dist.mean()[..., 0],
reference_forecast_dist.stddev()[..., 0]))
self.assertAllClose(predictive_mean[..., -num_forecast_steps:],
reference_forecast_mean,
atol=1.0 if use_slope else 0.3)
self.assertAllClose(predictive_stddev[..., -num_forecast_steps:],
reference_forecast_stddev,
atol=2.0 if use_slope else 1.0)
def test_forecasts_match_reference(self, use_slope):
seed = test_util.test_seed()
num_observed_steps = 5
num_forecast_steps = 4
model, observed_time_series, is_missing = self._build_test_model(
num_timesteps=num_observed_steps + num_forecast_steps,
true_slope_scale=0.5 if use_slope else None,
batch_shape=[3])
samples = tf.function(lambda: gibbs_sampler.fit_with_gibbs_sampling( # pylint: disable=g-long-lambda
model,
tfp.sts.MaskedTimeSeries(
observed_time_series[..., :num_observed_steps, tf.newaxis],
is_missing[..., :num_observed_steps]),
num_results=10000,
num_warmup_steps=100,
seed=seed))()
predictive_dist = gibbs_sampler.one_step_predictive(
model,
samples,
num_forecast_steps=num_forecast_steps,
thin_every=1)
predictive_mean, predictive_stddev = self.evaluate(
(predictive_dist.mean(), predictive_dist.stddev()))
self.assertAllEqual(predictive_mean.shape,
[3, num_observed_steps + num_forecast_steps])
self.assertAllEqual(predictive_stddev.shape,
[3, num_observed_steps + num_forecast_steps])
if use_slope:
parameter_samples = (samples.observation_noise_scale,
samples.level_scale, samples.slope_scale,
samples.weights)
else:
parameter_samples = (samples.observation_noise_scale,
samples.level_scale, samples.weights)
# Note that although we expect the Gibbs-sampled forecasts to match a
# reference implementation, we *don't* expect the one-step predictions to
# match `tfp.sts.one_step_predictive`, because that makes predictions using
# a filtered posterior (i.e., given only previous observations) whereas the
# Gibbs-sampled latent `level`s will incorporate some information from
# future observations.
reference_forecast_dist = tfp.sts.forecast(
model,
observed_time_series=observed_time_series[
..., :num_observed_steps],
parameter_samples=parameter_samples,
num_steps_forecast=num_forecast_steps)
reference_forecast_mean = self.evaluate(
reference_forecast_dist.mean()[..., 0])
reference_forecast_stddev = self.evaluate(
reference_forecast_dist.stddev()[..., 0])
self.assertAllClose(predictive_mean[..., -num_forecast_steps:],
reference_forecast_mean,
atol=1.0 if use_slope else 0.3)
self.assertAllClose(predictive_stddev[..., -num_forecast_steps:],
reference_forecast_stddev,
atol=2.0 if use_slope else 1.0)
