Speed up the matmul op, use the gemm replace the batch gemm (#22926)

In the op of gemm, we use the gemm to replace batch gemm, speed up the matmul op 

paddle/fluid/operators/matmul_op.cc

@@ -72,8 +72,21 @@ class MatMulKernel : public framework::OpKernel<T> {
         ColumnMatrixFromVector(y.dims()), 0, context.Attr<bool>("transpose_Y"));
     auto scale = static_cast<T>(context.Attr<float>("alpha"));
 
+    int head_number = 1;
+#if defined(PADDLE_WITH_MKLML) && !defined(PADDLE_WITH_CUDA)
+    head_number = context.Attr<int>("head_number");
+#endif
+
+    const auto &x_dims = x.dims();
+    const auto &y_dims = y.dims();
+    if (head_number <= 1 && x_dims.size() == 3 && y_dims.size() <= 2) {
+      // the transpose_X must be false, if is true, the transpose cost much time
+      if (!context.Attr<bool>("transpose_X")) {
+        mat_dim_a.height_ *= mat_dim_a.batch_size_;
+        mat_dim_a.batch_size_ = 0;
+      }
+    }
 #if defined(PADDLE_WITH_MKLML) && !defined(PADDLE_WITH_CUDA)
-    int head_number = context.Attr<int>("head_number");
     bool split_vertical_y = (mat_dim_a.width_ != mat_dim_b.height_);
 
     if (head_number > 1) {
@@ -210,6 +223,19 @@ class MatMulGradKernel : public framework::OpKernel<T> {
     auto blas = math::GetBlas<DeviceContext, T>(context);
     auto mat_dim_a = math::CreateMatrixDescriptor(a.dims(), 0, trans_a);
     auto mat_dim_b = math::CreateMatrixDescriptor(b.dims(), 0, trans_b);
+
+    int head_number = 1;
+#if defined(PADDLE_WITH_MKLML) && !defined(PADDLE_WITH_CUDA)
+    head_number = context.Attr<int>("head_number");
+#endif
+
+    if (head_number <= 1 && a.dims().size() == 3 && b.dims().size() <= 2) {
+      // the transpose_X must be false, if is true, the transpose cost much time
+      if (!trans_a) {
+        mat_dim_a.height_ *= mat_dim_a.batch_size_;
+        mat_dim_a.batch_size_ = 0;
+      }
+    }
     blas.MatMul(a, mat_dim_a, b, mat_dim_b,
                 static_cast<T>(context.Attr<float>("alpha")), out, T(0));
   }