Sigmoid Bijector¤
distreqx.bijectors.sigmoid.Sigmoid (AbstractFowardInverseBijector, AbstractInvLogDetJacBijector)
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A bijector that computes the logistic sigmoid.
The log-determinant implementation in this bijector is more numerically stable than relying on the automatic differentiation approach used by Lambda, so this bijector should be preferred over Lambda(jax.nn.sigmoid) where possible.
Note that the underlying implementation of jax.nn.sigmoid used by the
forward function of this bijector does not support inputs of integer type.
To invoke the forward function of this bijector on an argument of integer
type, it should first be cast explicitly to a floating point type.
When the absolute value of the input is large, Sigmoid becomes close to a
constant, so that it is not possible to recover the input x from the output
y within machine precision. In cases where it is needed to compute both the
forward mapping and the backward mapping one after the other to recover the
original input x, it is the user's responsibility to simplify the operation
to avoid numerical issues. One example of such case is to use the bijector
within a Transformed distribution and to obtain the log-probability of
samples obtained from the distribution's sample method. For values of the
samples for which it is not possible to apply the inverse bijector accurately,
log_prob returns NaN. This can be avoided by using sample_and_log_prob
instead of sample followed by log_prob.