def test_default_kwargs_throw_error_on_compression(self): noisy = uniform_noise.NoisyNormal(loc=.25, scale=10.) em = ContinuousBatchedEntropyModel(noisy, 1) x = tf.zeros(10) with self.assertRaises(RuntimeError): em.compress(x) s = tf.zeros(10, dtype=tf.string) with self.assertRaises(RuntimeError): em.decompress(s, [10])
def test_compression_works_after_serialization_no_offset(self): noisy = uniform_noise.NoisyNormal(loc=0, scale=5.) em = ContinuousBatchedEntropyModel(noisy, 1, compression=True) self.assertIs(em._quantization_offset, None) json = tf.keras.utils.serialize_keras_object(em) weights = em.get_weights() x = noisy.base.sample([100]) x_quantized = em.quantize(x) x_compressed = em.compress(x) em = tf.keras.utils.deserialize_keras_object(json) em.set_weights(weights) self.assertAllEqual(em.compress(x), x_compressed) self.assertAllEqual(em.decompress(x_compressed, [100]), x_quantized)
def test_compression_consistent_with_quantization(self): noisy = uniform_noise.NoisyNormal(loc=.25, scale=10.) em = ContinuousBatchedEntropyModel(noisy, 1, compression=True) x = noisy.base.sample([100]) x_quantized = em.quantize(x) x_decompressed = em.decompress(em.compress(x), [100]) self.assertAllEqual(x_decompressed, x_quantized)
class Compressor: def compress(self, values): if not hasattr(self, "em"): self.em = ContinuousBatchedEntropyModel(noisy, 1, compression=True) compressed = self.em.compress(values) return self.em.decompress(compressed, [100])
def test_high_entropy_bounds(self): # For high entropy distributions, the training bound should be very tight, # and the overhead of range coding manageable. noisy = uniform_noise.NoisyNormal(loc=0., scale=100.) em = ContinuousBatchedEntropyModel(noisy, 1, compression=True) x = noisy.base.sample([10000]) bits_eval = em.bits(x, training=False) bits_training = em.bits(x, training=True) bits_compressed = 8 * len(em.compress(x).numpy()) self.assertAllClose(bits_training, bits_eval, atol=0, rtol=5e-5) self.assertAllClose(bits_compressed, bits_eval, atol=0, rtol=5e-3)
def test_information_bounds(self): # `bits(training=True)` should be greater than `bits(training=False)` # because it is defined as an upper bound (albeit for infinite data). The # actual length of the bit string should always be greater than # `bits(training=False)` because range coding is only asymptotically # optimal, and because it operates on quantized probabilities. for scale in 2 ** tf.linspace(-2., 7., 10): noisy = uniform_noise.NoisyNormal(loc=0., scale=scale) em = ContinuousBatchedEntropyModel(noisy, 1, compression=True) x = noisy.base.sample([10000]) bits_eval = em.bits(x, training=False) bits_training = em.bits(x, training=True) bits_compressed = 8 * len(em.compress(x).numpy()) self.assertGreater(bits_training, .9975 * bits_eval) self.assertGreater(bits_compressed, bits_eval)
def test_small_bitcost_for_dirac_prior(self): prior = uniform_noise.NoisyNormal(loc=100 * tf.range(16.0), scale=1e-10) em = ContinuousBatchedEntropyModel( prior, coding_rank=2, compression=True) num_symbols = 1000 source = prior.base x = source.sample((3, num_symbols)) _, bits_estimate = em(x, training=True) bitstring = em.compress(x) x_decoded = em.decompress(bitstring, (num_symbols,)) bitstring_bits = tf.reshape( [len(b) * 8 for b in bitstring.numpy().flatten()], bitstring.shape) # Max 2 bytes. self.assertAllLessEqual(bits_estimate, 16) self.assertAllLessEqual(bitstring_bits, 16) # Quantization noise should be between -.5 and .5 self.assertAllLessEqual(tf.abs(x - x_decoded), 0.5)
def test_information_bounds(self, scale): # Off-center prior to test quantization offset heuristic. Without it, it # should be harder to achieve the bounds below. prior = uniform_noise.NoisyNormal(loc=.5, scale=scale) em = ContinuousBatchedEntropyModel(prior, coding_rank=1, compression=True) x = prior.base.sample([1000000]) _, bits_eval = em(x, training=False) _, bits_training = em(x, training=True) bits_compressed = 8 * len(em.compress(x).numpy()) # Asymptotically, the entropy estimate with `training=True` is an upper # bound on the entropy estimate with `training=False`. (With limited data, # fluctuations are possible.) with self.subTest("training bits > eval bits"): # Sample size is too small for the bound to be asymptotic. Increasing it # would make tests run too long. self.assertGreater(bits_training, 0.999999 * bits_eval) # Asymptotically, the length of the bit string should be greater than the # entropy estimate with `training=False` because range coding is only # asymptotically optimal, and because it operates on quantized # probabilities. with self.subTest("compressed bits > eval bits"): self.assertGreater(bits_compressed, bits_eval) # For low entropy distributions, the training bound can be very loose. if scale <= .5: with self.subTest("training bound loose"): self.assertAllClose(bits_training, bits_eval, atol=0, rtol=1.25) self.assertNotAllClose(bits_training, bits_eval, atol=0, rtol=1e-2) # For high entropy distributions, the training bound should be tight. if scale >= 64: with self.subTest("training bound tight"): self.assertAllClose(bits_training, bits_eval, atol=0, rtol=1e-5) # The overhead of range coding should always be manageable. with self.subTest("range coding overhead"): self.assertAllClose(bits_compressed, bits_eval, atol=0, rtol=5e-3)
def test_dtypes_are_correct_with_mixed_precision(self): tf.keras.mixed_precision.set_global_policy("mixed_float16") try: noisy = uniform_noise.NoisyNormal( loc=tf.constant(0, dtype=tf.float64), scale=tf.constant(1, dtype=tf.float64)) em = ContinuousBatchedEntropyModel(noisy, 1, compression=True) self.assertEqual(em.bottleneck_dtype, tf.float16) self.assertEqual(em.prior.dtype, tf.float64) x = tf.random.stateless_normal((2, 5), seed=(0, 1), dtype=tf.float16) x_tilde, bits = em(x) bitstring = em.compress(x) x_hat = em.decompress(bitstring, (5, )) self.assertEqual(x_hat.dtype, tf.float16) self.assertAllClose(x, x_hat, rtol=0, atol=.5) self.assertEqual(x_tilde.dtype, tf.float16) self.assertAllClose(x, x_tilde, rtol=0, atol=.5) self.assertEqual(bits.dtype, tf.float64) self.assertEqual(bits.shape, (2, )) self.assertAllGreaterEqual(bits, 0.) finally: tf.keras.mixed_precision.set_global_policy(None)