From abfd9fdd22c135e3e4048ef1d7fdf05e86a8939f Mon Sep 17 00:00:00 2001
From: tensor-tang <jian.j.tang@intel.com>
Date: Fri, 22 Sep 2017 23:28:28 +0800
Subject: [PATCH] add clip to avoid log zero and nan

---
 paddle/math/Matrix.cpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/paddle/math/Matrix.cpp b/paddle/math/Matrix.cpp
index 0023b4d0f5d..588310fbeec 100644
--- a/paddle/math/Matrix.cpp
+++ b/paddle/math/Matrix.cpp
@@ -3637,7 +3637,7 @@ void CpuMatrix::oneHotCrossEntropy(Matrix& output, IVector& label) {
   for (size_t i = 0; i < numSamples; ++i, out += dim) {
     CHECK_GE(lbl[i], 0);
     CHECK_LT((size_t)lbl[i], dim);
-    cost[i] = -std::log(out[lbl[i]]);
+    cost[i] = -std::log(std::max(out[lbl[i]], real(FLT_MIN)));
   }
 }
 
@@ -3652,7 +3652,7 @@ void CpuMatrix::oneHotCrossEntropyBp(Matrix& output, IVector& label) {
   real* grad = getData();
   int* lbl = label.getData();
   for (size_t i = 0; i < numSamples; ++i, out += dim, grad += dim) {
-    grad[lbl[i]] -= 1 / out[lbl[i]];
+    grad[lbl[i]] -= 1 / std::max(out[lbl[i]], real(FLT_MIN));
   }
 }
 
-- 
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