From bf4a866109667bea8c7fa142d940ef00f46fc2d6 Mon Sep 17 00:00:00 2001
From: Wenkai Du <wenkai.du@amd.com>
Date: Mon, 19 Oct 2020 14:06:23 -0400
Subject: [PATCH] Uses nullptr as send buffer for non-root ranks during scatter

---
 src/scatter.cu | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/scatter.cu b/src/scatter.cu
index 4dbbda25a3..b18ed382ce 100644
--- a/src/scatter.cu
+++ b/src/scatter.cu
@@ -86,7 +86,10 @@ testResult_t ScatterRunColl(void* sendbuff, void* recvbuff, size_t count, ncclDa
   return testNcclError;
 #else
 #if defined(RCCL_GATHER_SCATTER) && defined(USE_RCCL_GATHER_SCATTER)
-  NCCLCHECK(ncclScatter(sendbuff, recvbuff, count, type, root, comm, stream));
+  if (rank == root)
+    NCCLCHECK(ncclScatter(sendbuff, recvbuff, count, type, root, comm, stream));
+  else
+    NCCLCHECK(ncclScatter(0, recvbuff, count, type, root, comm, stream));
 #else
   NCCLCHECK(ncclGroupStart());
   if (rank == root) {