!7051 Fixed zero plus neg_inf issue under fp16

Merge pull request !7051 from XunDeng/pp_issue_branch

mindspore/nn/probability/distribution/transformed_distribution.py

@@ -13,7 +13,9 @@
 # limitations under the License.
 # ============================================================================
 """Transformed Distribution"""
+import numpy as np
 from mindspore._checkparam import Validator as validator
+from mindspore.ops import operations as P
 import mindspore.nn as nn
 from .distribution import Distribution
 from ._utils.utils import raise_not_impl_error
@@ -80,6 +82,8 @@ class TransformedDistribution(Distribution):
         self.parameter_names = distribution.parameter_names
         self.exp = exp_generic
         self.log = log_generic
+        self.equal_base = P.Equal()
+        self.select_base = P.Select()
 
     @property
     def bijector(self):
@@ -125,7 +129,8 @@ class TransformedDistribution(Distribution):
         inverse_value = self.bijector("inverse", value)
         unadjust_prob = self.distribution("log_prob", inverse_value, *args, **kwargs)
         log_jacobian = self.bijector("inverse_log_jacobian", value)
-        return unadjust_prob + log_jacobian
+        isneginf = self.equal_base(unadjust_prob, -np.inf)
+        return self.select_base(isneginf, unadjust_prob, unadjust_prob + log_jacobian)
 
     def _prob(self, value, *args, **kwargs):
         return self.exp(self._log_prob(value, *args, **kwargs))