tensorflow / tensorflow/probability
What does the method get_weights return in the case of Bayesian layers?
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Description
If you execute the following code
import numpy as np
import tensorflow as tf
import tensorflow_probability as tfp
input = tf.keras.layers.Input(shape=(1,))
layer = tfp.layers.DenseReparameterization(2)
x = layer(input)
model = tf.keras.models.Model(inputs=input, outputs=x)
inp = np.array([[1]])
print(model.predict(inp))
print("weights =", layer.get_weights())
print("layer.kernel_posterior.mean() =", layer.kernel_posterior.mean())
print("layer.kernel_posterior.stddev() =", layer.kernel_posterior.stddev())
print("layer.kernel_prior.mean() =", layer.kernel_prior.mean())
print("layer.kernel_prior.stddev() =", layer.kernel_prior.stddev())
print("layer.bias_posterior.mean() =", layer.bias_posterior.mean())
print("layer.bias_posterior.stddev() =", layer.bias_posterior.stddev())
You will get something like
[[0.07018379 0.13365692]]
weights = [
array([[0.01465803, 0.04191336]], dtype=float32),
array([[-2.9708524, -2.859167 ]], dtype=float32),
array([0.11541488, 0.1064656 ], dtype=float32)
]
layer.kernel_posterior.mean() = tf.Tensor([[0.01465803 0.04191336]], shape=(1, 2), dtype=float32)
layer.kernel_posterior.stddev() = tf.Tensor([[0.04998922 0.05573414]], shape=(1, 2), dtype=float32)
layer.kernel_prior.mean() = tf.Tensor([[0. 0.]], shape=(1, 2), dtype=float32)
layer.kernel_prior.stddev() = tf.Tensor([[1. 1.]], shape=(1, 2), dtype=float32)
layer.bias_posterior.mean() = tf.Tensor([0.11541488 0.1064656 ], shape=(2,), dtype=float32)
layer.bias_posterior.stddev() = tf.Tensor([0. 0.], shape=(2,), dtype=float32)
So, layer.get_weights(), where layer = tfp.layers.DenseReparameterization(2), returns a list of 3 arrays. The first array corresponds to the means of kernel_posterior and the last array corresponds to the means of bias_posterior. What does the second array array([[-2.9708524, -2.859167 ]], dtype=float32) correspond to?
Furthermore, why aren't the standard deviations also weights?
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
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Research direction
Run the minimal reproduction in the issue and inspect DenseReparameterization, get_weights, kernel_posterior, and bias_posterior behavior. Done when the documentation or issue response clearly identifies the second returned array and explains why posterior standard deviations are not returned as separate weights.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- machine-learning
- Issue type
- Documentation
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 35/100