anirudhacharya commented on a change in pull request #12697: [MXNET -1004] 
Poisson NegativeLog Likelihood loss
URL: https://github.com/apache/incubator-mxnet/pull/12697#discussion_r223536222
 
 

 ##########
 File path: python/mxnet/gluon/loss.py
 ##########
 @@ -706,3 +707,65 @@ def hybrid_forward(self, F, pred, positive, negative):
                      axis=self._batch_axis, exclude=True)
         loss = F.relu(loss + self._margin)
         return _apply_weighting(F, loss, self._weight, None)
+
+
+class PoissonNLLLoss(Loss):
+    r"""For a target (Random Variable) in a Poisson distribution, the function 
calculates the Negative
+    Log likelihood loss.
+    PoissonNLLLoss measures the loss accrued from a poisson regression 
prediction made by the model.
+
+    .. math::
+        L = \text{pred} - \text{target} * \log(\text{pred}) 
+\log(\text{target!})
+
+    `pred`, `target` can have arbitrary shape as long as they have the same 
number of elements.
+
+    Parameters
+    ----------
+    from_logits : boolean, default True
+        indicating whether log(predicted) value has already been computed. If 
True, the loss is computed as
+        :math:`\exp(\text{pred}) - \text{target} * \text{pred}`, and if False, 
then loss is computed as
+        :math:`\text{pred} - \text{target} * 
\log(\text{pred}+\text{epsislon})`.The default value
 
 Review comment:
   these definitions seem to be at odds with the definition given above in line 
718

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