Merge pull request #4777 from cxysteven/develop

lambdaCost layer's bug fix
8 years ago · 5c5250e3e0
parent 44ed21eea5 60c2536d22
commit 5c5250e3e0
1 changed files with 2 additions and 2 deletions
--- a/paddle/gserver/layers/CostLayer.cpp
+++ b/paddle/gserver/layers/CostLayer.cpp
@ -462,8 +462,8 @@ void LambdaCost::calcGrad(const real* outputScore,
      real score_j = score[index_j];
      real dcgDif = 0;
      if (j < sortSize) {
-        dcgDif = (std::pow(2, score_i) - std::pow(2, score_j)) /
-                 (std::log(i + 2) - std::log(j + 2));
+        dcgDif = (std::pow(2, score_i) - std::pow(2, score_j)) *
+                 (1 / std::log(i + 2) - 1 / std::log(j + 2));
      } else {
        dcgDif =
            (std::pow(2, score_i) - std::pow(2, score_j)) / std::log(i + 2);