[mkldnn] Fix elementwise_sub sign reverse for mkldnn (#46049)

* fix sub sign reverse for mkldnn

* refactor code as comment

* remove useless

* format code

paddle/fluid/operators/elementwise/mkldnn/elementwise_mkldnn_op.h

@@ -149,12 +149,20 @@ class EltwiseMKLDNNGradKernel : public ElemwiseGradKernel<T> {
     auto* dx = ctx.Output<Tensor>(framework::GradVarName("X"));
     auto* dy = ctx.Output<Tensor>(framework::GradVarName("Y"));
     auto* dout = ctx.Input<Tensor>(framework::GradVarName("Out"));
+    VLOG(4) << "element sub: dx " << dx << " dy " << dy << " dout " << dout;
 
     // oneDNN's binary is optimized for broadcasting y into x, so in other case
     // we have to swap tensors to achieve optimal performance
+    bool swap_x_y = false;
     if (x->numel() < y->numel()) {
       std::swap(x, y);
       std::swap(dx, dy);
+      swap_x_y = true;
+    }
+
+    std::vector<float> scales{1.0};
+    if (swap_x_y) {
+      scales[0] = (BINARY_OP == dnnl::algorithm::binary_add) ? 1 : -1;
     }
 
     int axis = ctx.Attr<int>("axis");
@@ -172,7 +180,6 @@ class EltwiseMKLDNNGradKernel : public ElemwiseGradKernel<T> {
         dout->mem_desc(), platform::to_void_cast(dout->data<T>()));
 
     auto& astream = platform::MKLDNNDeviceContext::tls().get_stream();
-
     if (dx) {
       std::shared_ptr<dnnl::memory> dst_memory;
 
@@ -181,8 +188,11 @@ class EltwiseMKLDNNGradKernel : public ElemwiseGradKernel<T> {
           BINARY_OP == dnnl::algorithm::binary_sub) {
         dst_memory = reorder_handler.AcquireDstMemory(
             dx, dout->mem_desc(), ctx.GetPlace());
-        auto reorder_p =
-            reorder_handler.AcquireReorder(dst_memory, reorder_src_memory_p);
+
+        dnnl::primitive_attr reorder_attr;
+        reorder_attr.set_output_scales(0, scales);
+        auto reorder_p = reorder_handler.AcquireReorder(
+            dst_memory, reorder_src_memory_p, reorder_attr);
         platform::RecordEvent record_reorder(
             "int_reorder",
             platform::TracerEventType::UserDefined,
@@ -190,6 +200,7 @@ class EltwiseMKLDNNGradKernel : public ElemwiseGradKernel<T> {
             platform::EventRole::kUniqueOp);
 
         reorder_p->execute(astream, *reorder_src_memory_p, *dst_memory);
+
       } else {  // elementwise_mul & elementwise_div
         platform::BinaryMKLDNNHandler<T> binary_handler(BINARY_OP,
                                                         axis,
@@ -233,11 +244,10 @@ class EltwiseMKLDNNGradKernel : public ElemwiseGradKernel<T> {
               dy, dout->mem_desc(), ctx.GetPlace());
 
           dnnl::primitive_attr reorder_attr;
-          std::vector<float> scales(1);
-          scales[0] = (BINARY_OP == dnnl::algorithm::binary_add) ? 1 : -1;
           reorder_attr.set_output_scales(0, scales);
-          auto reorder_p = std::make_shared<dnnl::reorder>(
-              *(reorder_src_memory_p), *(reorder_dst_memory_p), reorder_attr);
+
+          auto reorder_p = reorder_handler.AcquireReorder(
+              reorder_dst_memory_p, reorder_src_memory_p, reorder_attr);
           platform::RecordEvent record_reorder(
               "int_reorder",
               platform::TracerEventType::UserDefined,
@@ -331,7 +341,8 @@ class EltwiseMKLDNNGradKernel : public ElemwiseGradKernel<T> {
         // Broadcasting
         if (BINARY_OP == dnnl::algorithm::binary_sub) {
           dnnl::post_ops po;
-          po.append_eltwise(1.0f, dnnl::algorithm::eltwise_linear, -1.0f, 0);
+          po.append_eltwise(
+              1.0f, dnnl::algorithm::eltwise_linear, scales[0], 0);
           broadcast_reduction_attr.set_post_ops(po);
         }
 

paddle/phi/backends/onednn/onednn_reuse.h

@@ -877,6 +877,10 @@ class BinaryOneDNNHandler : public OneDNNHandlerNoCachingT<T, dnnl::binary> {
         CreateAttributes(algo, scale_x, scale_y, scale_out, post_ops);
 
     if (x->numel() < y->numel()) {
+      if (algo == dnnl::algorithm::binary_sub) {
+        attributes = CreateAttributes(
+            algo, -1.0 * scale_x, -1.0 * scale_y, scale_out, post_ops);
+      }
       this->AcquireForwardPrimitiveDescriptor(
           attributes, algo, src1_md, src0_md, dst_md);
     } else {

python/paddle/fluid/tests/unittests/mkldnn/test_elementwise_sub_mkldnn_op.py

@@ -89,6 +89,23 @@ class TestMKLDNNElementwiseSubOp4(TestMKLDNNElementwiseSubOp):
         self.out = np.subtract(self.x, self.y)
 
 
+class TestMKLDNNElementwiseSubOp40(TestMKLDNNElementwiseSubOp):
+
+    def init_input_output(self):
+        self.x = np.random.uniform(0.1, 2, [180, 1]).astype(self.dtype)
+        self.y = np.random.uniform(0.1, 1, [1, 256]).astype(self.dtype)
+        self.out = np.subtract(self.x, self.y)
+
+    def test_check_grad_normal(self):
+        self.check_grad(['X', 'Y'], 'Out')
+
+    def test_check_grad_ignore_x(self):
+        self.check_grad(['Y'], 'Out', no_grad_set=set("X"))
+
+    def test_check_grad_ignore_y(self):
+        self.check_grad(['X'], 'Out', no_grad_set=set('Y'))
+
+
 class TestMKLDNNElementwiseSubOp5(TestMKLDNNElementwiseSubOp):
 
     def init_input_output(self):