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[WIP] Implement nnabla.experimental.distributions #565

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takuseno
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Squashed version of #392 .

cc. @TE-AkioHayakawa

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@takuseno
Sorry for not getting back to you sooner.
Thank you again for your contribution!

I have reviewed your code. Please reflect my comments.

else:
ref_sample = ref_sample_fn(*params, shape=(10000, 10))

assert np.allclose(sample.d.mean(), ref_sample.mean(), atol=3e-2,
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Please use nnabla.testing.assert_allclose rather than numpy.allclose.

Comment on lines 35 to 37
loc (~nnabla.Variable): N-D array of :math:`\mu` in definition.
scale (~nnabla.Variable): N-D array of diagonal entries of :math:`L`
such that covariance matrix :math:`\Sigma = L L^T`.
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I think these two args also accept numpy array, don't they?

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If not, I think we should implement as numpy array could be used as well.

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I expect it takes nn.Variable because equations in all methods of this class are differentiable. And, since the purpose of these classes is to easily build differentiable distributions, I don't think it is necessary to take numpy arrays, however it will be good for use. Then, I'll make numpy arrays acceptable in those classes.

Comment on lines 33 to 34
loc (~nnabla.Variable): N-D array of :math:`\mu` in definition.
scale (~nnabla.Variable): N-D array of :math:`\sigma` in definition.
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Same above.

Comment on lines 29 to 30
low (~nnabla.Variable): N-D array of :math:`low` in definition.
high (~nnabla.Variable): N-D arraya of :math:`high` in definition.
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Same above.

class MultivariateNormal(Distribution):
"""Multivariate normal distribution.

Multivariate normal distribution defined as follows:
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Now MultivariateNormal only supports a diagonal matrix as covariance, right?
If so, I think "Multivariate normal distribution with diagonal covariance matrix" or something like this is better.


def scipy_fn(loc, scale):
return stats.multivariate_normal(np.reshape(loc, (-1,)),
np.reshape(scale, (-1,)))
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If we create diagonal matrix as covariance such as cov = scale @ scale.T (@ is matrix multiplication), we can delete following 3 functions and make distribution_test_util simpler, can't we?

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I'm not sure it is true but please try it.

@takuseno takuseno force-pushed the clean_implement_distribution branch from 2aa8449 to d3eed32 Compare January 9, 2020 05:47
@takuseno takuseno changed the title Implement nnabla.experimental.distributions [WIP] Implement nnabla.experimental.distributions Feb 19, 2020
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I've noticed that current prob methods are not appropriate to calculate gradients. I should make log_prob methods instead. I've put WIP sign in the title.

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2 participants