Mark CUDA 10.1 as unsupported. (#4265)

src/common/device_helpers.cuh

@@ -26,8 +26,9 @@
 #include "../common/io.h"
 #endif
 
-// Uncomment to enable
-#define TIMERS
+#if __CUDACC_VER_MAJOR__ == 10 && __CUDACC_VER_MINOR__ == 1
+#error "CUDA 10.1 is not supported, see #4264."
+#endif
 
 namespace dh {
 
@@ -893,14 +894,14 @@ class AllReducer {
     int nccl_nranks = std::accumulate(device_counts.begin(),
                         device_counts.end(), 0);
     nccl_rank += nccl_rank_offset;
-    
+
     GroupStart();
     for (size_t i = 0; i < device_ordinals.size(); i++) {
       int dev = device_ordinals.at(i);
       dh::safe_cuda(cudaSetDevice(dev));
       dh::safe_nccl(ncclCommInitRank(
         &comms.at(i),
-        nccl_nranks, id, 
+        nccl_nranks, id,
         nccl_rank));
 
       nccl_rank++;