From: vishwakftw <cs15btech11043@iith.ac.in>
Date: Thu, 10 Jan 2019 04:04:18 +0000 (-0800)
Subject: Fix log_prob for Gumbel distribution (#15878)
X-Git-Tag: accepted/tizen/6.5/unified/20211028.231830~1934
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=5f1dd9e7436366d2ea4580ebbaaba1a70b22b4c9;p=platform%2Fupstream%2Fpytorch.git

Fix log_prob for Gumbel distribution (#15878)

Summary:
Fixes https://github.com/pytorch/pytorch/issues/15681

Changelog:
- Add hard-coded implementation of log_prob
Pull Request resolved: https://github.com/pytorch/pytorch/pull/15878

Differential Revision: D13613716

Pulled By: soumith

fbshipit-source-id: 2ba74e52748b6213098b167940dcc068f0c056f4
---

diff --git a/torch/distributions/gumbel.py b/torch/distributions/gumbel.py
index 68aa29a..5bd3a2d 100644
--- a/torch/distributions/gumbel.py
+++ b/torch/distributions/gumbel.py
@@ -45,6 +45,13 @@ class Gumbel(TransformedDistribution):
         new.scale = self.scale.expand(batch_shape)
         return super(Gumbel, self).expand(batch_shape, _instance=new)
 
+    # Explicitly defining the log probability function for Gumbel due to precision issues
+    def log_prob(self, value):
+        if self._validate_args:
+            self._validate_sample(value)
+        y = (self.loc - value) / self.scale
+        return (y - y.exp()) - self.scale.log()
+
     @property
     def mean(self):
         return self.loc + self.scale * euler_constant