refine the threshold functions

Author: tensor-tang

paddle/fluid/operators/math/blas_impl.h

@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 #pragma once
+#include <limits>
 #include <vector>
 #include "paddle/fluid/operators/math/math_function.h"
 
@@ -161,6 +162,25 @@ struct CBlas<platform::float16> {
   }
 #endif
 };
+template <typename T>
+inline static bool UseXSMM(const int &m, const int &n, const int &k,
+                           bool transa, bool transb, const T &alpha,
+                           const T &beta) {
+#ifdef PADDLE_WITH_LIBXSMM
+  // Refer to https://github.com/hfp/libxsmm/blob/master/README.md
+  // But the threshold is custom
+  constexpr int LIBXSMM_THRESHOLD = 20 * 20 * 20;
+  if (m * n * k > LIBXSMM_THRESHOLD || transa || transb ||
+      std::abs<T>(alpha - static_cast<T>(1) >
+                  std::numeric_limits<T>::epsilon()) ||
+      std::abs<T>(beta) > std::numeric_limits<T>::epsilon()) {
+    return false;
+  } else {
+    return true;
+  }
+#endif
+  return false;
+}
 
 template <>
 template <typename T>
@@ -172,8 +192,8 @@ void Blas<platform::CPUDeviceContext>::GEMM(CBLAS_TRANSPOSE transA,
   int ldb = (transB == CblasNoTrans) ? N : K;
   int ldc = N;
 #ifdef PADDLE_WITH_LIBXSMM
-  if (M * N * K < 128 * 128 * 128 && transA == CblasNoTrans &&
-      transB == CblasNoTrans) {
+  if (UseXSMM(M, N, K, transA != CblasNoTrans, transB != CblasNoTrans, alpha,
+              beta)) {
     // refer to https://github.com/hfp/libxsmm/blob/master/README.md
     // Note: SMM use ColMajor
     const char transa = 'N';