Added creation of new tree and added switch for using treesplit for specific cases (#551)

tools/topo_expl/utils.cpp

@@ -789,6 +789,8 @@ ncclResult_t initTransportsRank_3(struct ncclComm* comm, struct allGather3Data_t
   NCCLCHECK(ncclCalloc(&rings, nranks*MAXCHANNELS));
   NCCLCHECK(ncclTopoPostset(comm, nodesFirstRank, nodesTreePatterns, allTopoRanks, rings, &collNetGraph, nc));
 
+  if (comm->topo->pivotA2ANumBiRings == 3) NCCLCHECK(ncclTreeBasePostset(comm, &treeGraph));
+
   free(allTopoRanks);
   free(nodesTreePatterns);
   free(nodesFirstRank);