fix bug of scatter op (#18640)

test=develop

paddle/fluid/operators/scatter_op.cc

@@ -58,10 +58,14 @@ class ScatterGradOp : public framework::OperatorWithKernel {
   using framework::OperatorWithKernel::OperatorWithKernel;
 
   void InferShape(framework::InferShapeContext* ctx) const override {
-    ctx->SetOutputDim(framework::GradVarName("Updates"),
-                      ctx->GetInputDim("Updates"));
-    ctx->SetOutputDim(framework::GradVarName("X"),
-                      ctx->GetInputDim(framework::GradVarName("Out")));
+    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:

paddle/fluid/operators/scatter_op.cu

@@ -47,12 +47,15 @@ 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"));
-
-    // In place gradient: dX = dO
-    dX->ShareDataWith(*dOut);
-    dUpdates->mutable_data<T>(ctx.GetPlace());
-    // Gradient by Gather: dUpdates = dO[Ids]
-    GPUGather<T>(ctx.device_context(), *dOut, *Ids, dUpdates);
+    if (dX) {
+      // In place gradient: dX = dO
+      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);
+    }
   }
 };
 

paddle/fluid/operators/scatter_op.h

@@ -74,11 +74,15 @@ class ScatterGradientOpKernel : public framework::OpKernel<T> {
     auto *Ids = ctx.Input<Tensor>("Ids");
     auto *dOut = ctx.Input<Tensor>(framework::GradVarName("Out"));
 
-    // In place gradient: dX = dO
-    framework::TensorCopySync(*dOut, ctx.GetPlace(), dX);
-    dUpdates->mutable_data<T>(ctx.GetPlace());
-    // Gradient by Gather: dUpdates = dO[Ids]
-    CPUGather<T>(ctx.device_context(), *dOut, *Ids, dUpdates);
+    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);
+    }
   }
 };