### `tf.nn.log_poisson_loss(targets, log_input, compute_full_loss=False, name=None)` {#log_poisson_loss}

Computes log Poisson loss given `log_input`.

Gives the log-likelihood loss between the prediction and the target under the
assumption that the target has a Poisson distribution.
Caveat: By default, this is not the exact loss, but the loss minus a
  constant term [log(z!)]. That has no effect for optimization, but
  does not play well with relative loss comparisons. To compute an
  approximation of the log factorial term, specify
  compute_full_loss=True to enable Stirling's Approximation.

For brevity, let `c = log(x) = log_input`, `z = targets`.  The log Poisson
loss is

      -log(exp(-x) * (x^z) / z!)
    = -log(exp(-x) * (x^z)) + log(z!)
    ~ -log(exp(-x)) - log(x^z) [+ z * log(z) - z + 0.5 * log(2 * pi * z)]
        [ Note the second term is the Stirling's Approximation for log(z!).
          It is invariant to x and does not affect optimization, though
          important for correct relative loss comparisons. It is only
          computed when compute_full_loss == True. ]
    = x - z * log(x) [+ z * log(z) - z + 0.5 * log(2 * pi * z)]
    = exp(c) - z * c [+ z * log(z) - z + 0.5 * log(2 * pi * z)]

##### Args:


*  <b>`targets`</b>: A `Tensor` of the same type and shape as `log_input`.
*  <b>`log_input`</b>: A `Tensor` of type `float32` or `float64`.
*  <b>`compute_full_loss`</b>: whether to compute the full loss. If false, a constant
    term is dropped in favor of more efficient optimization.
*  <b>`name`</b>: A name for the operation (optional).

##### Returns:

  A `Tensor` of the same shape as `log_input` with the componentwise
  logistic losses.

##### Raises:


*  <b>`ValueError`</b>: If `log_input` and `targets` do not have the same shape.