From 2b9a62a806bcd04a30b2dec69951404c9c917f77 Mon Sep 17 00:00:00 2001
From: Jiaming Yuan <jm.yuan@outlook.com>
Date: Tue, 7 Jan 2020 11:15:19 +0800
Subject: [PATCH] Throw error when not compiled with NCCL. (#5170)

---
 src/common/device_helpers.cu | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/common/device_helpers.cu b/src/common/device_helpers.cu
index 90b58649d..c30c55d90 100644
--- a/src/common/device_helpers.cu
+++ b/src/common/device_helpers.cu
@@ -71,6 +71,10 @@ void AllReducer::Init(int _device_ordinal) {
   dh::safe_nccl(ncclCommInitRank(&comm, rabit::GetWorldSize(), id, rank));
   safe_cuda(cudaStreamCreate(&stream));
   initialised_ = true;
+#else
+  if (rabit::IsDistributed()) {
+    LOG(FATAL) << "XGBoost is not compiled with NCCL.";
+  }
 #endif  // XGBOOST_USE_NCCL
 }