Fix compiling in cuDNN v5.

test=develop

paddle/fluid/operators/conv_cudnn_op.cu.cc

@@ -50,12 +50,18 @@ static constexpr char kCUDNNBwdFilterAlgoCache[] = "kCUDNNBwdFilterAlgoCache";
 static constexpr size_t kCONV_CUDNN_WORKSPACE_LIMIT_BYTES =
     static_cast<size_t>(1024) * 1024 * 1024;
 
-static constexpr size_t kNUM_CUDNN_FWD_ALGS =
-    CUDNN_CONVOLUTION_BWD_FILTER_ALGO_COUNT;
+#if CUDNN_VERSION_MIN(6, 0, 5)
+static constexpr size_t kNUM_CUDNN_FWD_ALGS = CUDNN_CONVOLUTION_FWD_ALGO_COUNT;
 static constexpr size_t kNUM_CUDNN_BWD_FILTER_ALGS =
     CUDNN_CONVOLUTION_BWD_FILTER_ALGO_COUNT;
 static constexpr size_t kNUM_CUDNN_BWD_DATA_ALGS =
     CUDNN_CONVOLUTION_BWD_DATA_ALGO_COUNT;
+#else
+// cuDNN v5 has no CUDNN_CONVOLUTION_FWD_ALGO_COUNT etc.
+static constexpr size_t kNUM_CUDNN_FWD_ALGS = 7;
+static constexpr size_t kNUM_CUDNN_BWD_FILTER_ALGS = 4;
+static constexpr size_t kNUM_CUDNN_BWD_DATA_ALGS = 5;
+#endif
 
 template <typename T>
 class CUDNNConvOpKernel : public framework::OpKernel<T> {