fix bug of scatter op (#18640)

test=develop

paddle/fluid/operators/scatter_op.cc

@@ -58,11 +58,15 @@ class ScatterGradOp : public framework::OperatorWithKernel {
   using framework::OperatorWithKernel::OperatorWithKernel;
 
   void InferShape(framework::InferShapeContext* ctx) const override {
+    if (ctx->HasOutput(framework::GradVarName("Updates"))) {
       ctx->SetOutputDim(framework::GradVarName("Updates"),
                         ctx->GetInputDim("Updates"));
+    }
+    if (ctx->HasOutput(framework::GradVarName("X"))) {
       ctx->SetOutputDim(framework::GradVarName("X"),
                         ctx->GetInputDim(framework::GradVarName("Out")));
     }
+  }
 
  protected:
   framework::OpKernelType GetExpectedKernelType(

paddle/fluid/operators/scatter_op.cu

@@ -47,13 +47,16 @@ class ScatterGradOpCUDAKernel : public framework::OpKernel<T> {
     auto *dUpdates = ctx.Output<Tensor>(framework::GradVarName("Updates"));
     auto *Ids = ctx.Input<Tensor>("Ids");
     auto *dOut = ctx.Input<Tensor>(framework::GradVarName("Out"));
-
+    if (dX) {
       // In place gradient: dX = dO
-    dX->ShareDataWith(*dOut);
+      framework::TensorCopy(*dOut, ctx.GetPlace(), dX);
+    }
+    if (dUpdates) {
       dUpdates->mutable_data<T>(ctx.GetPlace());
       // Gradient by Gather: dUpdates = dO[Ids]
       GPUGather<T>(ctx.device_context(), *dOut, *Ids, dUpdates);
     }
+  }
 };
 
 }  // namespace operators

paddle/fluid/operators/scatter_op.h

@@ -74,12 +74,16 @@ class ScatterGradientOpKernel : public framework::OpKernel<T> {
     auto *Ids = ctx.Input<Tensor>("Ids");
     auto *dOut = ctx.Input<Tensor>(framework::GradVarName("Out"));
 
+    if (dX) {
       // In place gradient: dX = dO
       framework::TensorCopySync(*dOut, ctx.GetPlace(), dX);
+    }
+    if (dUpdates) {
       dUpdates->mutable_data<T>(ctx.GetPlace());
       // Gradient by Gather: dUpdates = dO[Ids]
       CPUGather<T>(ctx.device_context(), *dOut, *Ids, dUpdates);
     }
+  }
 };
 
 }  // namespace operators