added a fence before the flag write

src/collectives/device/all_to_all.h

@@ -79,6 +79,7 @@ class ncclFunction<ncclFuncAllToAll, ALGO, PROTO, FUNC, T, UNROLL> {
           } else if (sckltb->type == SCKL_RECV) {
             prims.directRecv(thisbuffer + offset, offset, nelem);
             if (tid == 0){
+              __threadfence();
               uint64_t curFlag = COMPUTE_FLAG(workIndex, iter, i);
               scklFlags[bid].flag = curFlag;
             }

src/enqueue.cc

@@ -549,7 +549,7 @@ ncclResult_t ncclSaveCommKernels(ncclComm_t comm) {
     for (int c = 0; c < comm->asyncOpCount; c++) {
       struct ncclInfo* info = comm->asyncOps+c;
       if (hasScklAlgo && info->algorithm != NCCL_ALGO_SCKL){
-        WARN("SCKL algorithms can be used asynchronously only when all are the same algorithm.");
+        WARN("SCKL algorithms can only be used asynchronously with other SCKL algorithm.");
         return ncclInvalidUsage;
       }
       // SCKL needs to adjust nChannels in the future