diff --git a/src/collectives/device/all_reduce.h b/src/collectives/device/all_reduce.h
index c92ce89d33..2ee9dc0f22 100644
--- a/src/collectives/device/all_reduce.h
+++ b/src/collectives/device/all_reduce.h
@@ -205,7 +205,6 @@ namespace {
                    /* LL128 */       : nthreads*(Proto::calcBytePerGrain()/sizeof(T))/8);
     const ssize_t loopSize = int(nChannels*chunkSize);
     const ssize_t size = args->count;
-
     int nthreadsSplit;
     if (Proto::Id == NCCL_PROTO_SIMPLE) {
       nthreadsSplit = nthreads/2;
@@ -400,7 +399,8 @@ struct RunWorkElement<ncclFuncAllReduce, T, RedOp, NCCL_ALGO_RING, NCCL_PROTO_LL
 template<typename T, typename RedOp>
 struct RunWorkElement<ncclFuncAllReduce, T, RedOp, NCCL_ALGO_TREE, NCCL_PROTO_LL> {
   __device__ __attribute__((noinline)) void run(ncclWorkElem *args) {
-    runTreeUpDown<T, RedOp, ProtoLL>(args);
+    if (args->pad_0 == 0) runTreeUpDown<T, RedOp, ProtoLL>(args);
+    else runTreeSplit<T, RedOp, ProtoLL>(args);
   }
 };
 
diff --git a/src/enqueue.cc b/src/enqueue.cc
index 7e8ffb8b64..ef76aac9cc 100644
--- a/src/enqueue.cc
+++ b/src/enqueue.cc
@@ -451,6 +451,31 @@ static ncclResult_t getAlgoInfo(struct ncclInfo* info, int collNetTypeSupport, i
   if (info->coll == ncclFuncAllToAllPivot) {
     int pivotA2ANumUniRings = comm->topo->pivotA2ANumBiRings * 2;
     info->nChannels = comm->nChannels / pivotA2ANumUniRings * pivotA2ANumUniRings;
+   } else if (info->coll == ncclFuncAllReduce && comm->topo->pivotA2ANumBiRings == 3) {
+    static int userTuneInput = -2;
+    if (userTuneInput == -2) {
+      const char *protoStr = getenv("NCCL_PROTO");
+      const char *algoStr = getenv("NCCL_ALGO");
+      if (!protoStr && !algoStr)
+        userTuneInput = 0;
+      else
+        userTuneInput = 1;
+    }
+    info->nChannels = nc;
+    if (!userTuneInput) {
+      // always respect user settings
+      if (info->nBytes <= 196608) {
+        info->protocol = NCCL_PROTO_LL;
+        info->algorithm = NCCL_ALGO_TREE;
+        info->nChannels =  std::min(comm->nChannels, info->nBytes <= 65536? 4 : 12);
+      } else if (info->nBytes <= 1048576) {
+        info->protocol = NCCL_PROTO_LL;
+        info->algorithm = NCCL_ALGO_RING;
+      } else {
+        info->protocol = NCCL_PROTO_SIMPLE;
+        info->algorithm = NCCL_ALGO_RING;
+      }
+    }
   } else if (comm->topo->nodes[GPU].nodes[0].gpu.gcn == 910 && comm->topo->tuning == 4 &&
     ((comm->nNodes == 2 && info->nBytes == 33554432) || (comm->nNodes <= 4 && info->nBytes == 67108864))) {
     static int userTuneInput = -2;
@@ -532,7 +557,7 @@ comp_next:
   // Set nstepsPerLoop and nchunksPerLoop
   NCCLCHECK(getPatternInfo(info));
   NCCLCHECK(getLoopInfo(info));
-
+  if (info->comm->topo->pivotA2ANumBiRings == 3 ) work->pad_0 = 1;
   work->opCount = info->opCount;
   work->header.type = ncclWorkTypeColl;
   work->sendbuff = info->sendbuff;
@@ -543,7 +568,6 @@ comp_next:
   work->header.nWarps = info->nThreads / info->comm->WarpSize;
   work->redOpArg = info->opFull.scalarArg;
   work->redOpArgIsPtr = info->opFull.scalarArgIsPtr;
-
   if (info->comm->nRanks == 1) {
     // one-rank reduce index
     work->header.funcIndex = FUNC_INDEX_P2P - ncclNumTypes + int(info->datatype);
diff --git a/src/graph/connect.cc b/src/graph/connect.cc
index 0c3ba56629..2c211df88c 100644
--- a/src/graph/connect.cc
+++ b/src/graph/connect.cc
@@ -66,6 +66,88 @@ ncclResult_t ncclTopoPreset(struct ncclComm* comm,
   return ncclSuccess;
 }
 
+ncclResult_t ncclTreeBasePostset(struct ncclComm* comm,
+    struct ncclTopoGraph* treeGraph) {
+  // int rank = comm->rank;
+  // int localRanks = comm->topo->nodes[GPU].count;
+  int nChannels = comm->nChannels;
+  int ring[NCCL_TOPO_MAX_NODES][NCCL_TOPO_MAX_NODES];
+  int xLimit = 0, yLimit = 0;
+  for (int j=0; j < NCCL_TOPO_MAX_NODES; j++) {
+    if (treeGraph->treeBase[0][j]  == -1) {
+      xLimit = j;
+      break;
+    }
+  }
+  for (int k=0; k < NCCL_TOPO_MAX_NODES; k++) {
+    if (treeGraph->treeBase[k][0]  == -1) {
+      yLimit = k;
+      break;
+    }
+  }
+  for (int j=0; j < xLimit; j++) {
+    for (int k=0; k < yLimit; k++)
+      ring[k][j] = treeGraph->treeBase[k][j];
+  }
+
+  //new tree
+  for (int c=0; c<nChannels; c++) {
+    struct ncclChannel* channel = comm->channels+c;
+    int ringPrev, ringNext;
+    int treeRoot = c%comm->nRanks;
+    int curRank = comm->rank;
+    int curRankNeighborUp, curRankNeighborDown;
+    int rootRing, nextRing;
+    int rootIndex = 0;
+    int arrayIndex;
+    for (int j=0; j < xLimit; j++) {
+      for (int k=0; k < yLimit; k++) {
+        if (treeRoot == ring[k][j]) {
+          rootRing = k;
+          rootIndex = j;
+        }
+        if (curRank == ring[k][j]) {
+          arrayIndex = j;
+          if (k > 0) curRankNeighborUp=ring[k-1][j];
+          else curRankNeighborUp=ring[yLimit-1][j];
+          if (k < yLimit-1) {
+            curRankNeighborDown=ring[k+1][j];
+            nextRing = k+1;
+          }
+          else {
+            curRankNeighborDown = ring[0][j];
+            nextRing = 0;
+          }
+        }
+      }
+    }
+
+    if ((curRank != ring[rootRing][arrayIndex])) {
+      channel->tree.up = curRankNeighborUp;
+      channel->tree.down[0] = nextRing==rootRing ? -1 : curRankNeighborDown;
+      channel->tree.down[1] = -1;
+    }
+    else {
+      if (arrayIndex > 0) ringPrev=ring[rootRing][arrayIndex-1];
+      else ringPrev=ring[rootRing][xLimit-1];
+      if (arrayIndex < xLimit-1) ringNext=ring[rootRing][arrayIndex+1];
+      else ringNext=ring[rootRing][0];
+      if ((c/2)%2 == 1) {
+        int temp = ringPrev;
+        ringPrev = ringNext;
+        ringNext = temp;
+      }
+      channel->tree.up = treeRoot == curRank ? -1 : ringPrev;
+      channel->tree.down[0] = curRankNeighborDown;
+      channel->tree.down[1] = ringNext == treeRoot ? -1 : ringNext;
+    }
+    channel->tree.down[2] = -1; // cleanup
+  }
+
+
+  return ncclSuccess;
+}
+
 static ncclResult_t connectRings(struct ncclComm* comm, int* ringRecv, int* ringSend, int* ringPrev, int* ringNext, int* firstRanks) {
   int nChannels = comm->nChannels;
   int nNodes = comm->nNodes;
diff --git a/src/graph/rome_models.cc b/src/graph/rome_models.cc
index e1c98f6a0e..7c02dd4800 100644
--- a/src/graph/rome_models.cc
+++ b/src/graph/rome_models.cc
@@ -43,6 +43,7 @@ struct rcclRomeModel {
   const char *pattern;
   const char *ringBase;
   const char *options;
+  const char *treeBase;
 };
 
 static struct rcclRomeModel rome_model_22 = {
@@ -56,6 +57,7 @@ static struct rcclRomeModel rome_model_22 = {
   .pattern = "10302120",
   .ringBase = "7 4 5 3 1 0 6 2|4 7 3 5 0 1 2 6",
   .options = "",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_25 = {
@@ -69,6 +71,7 @@ static struct rcclRomeModel rome_model_25 = {
   .pattern = "11303011",
   .ringBase = "2 1 0 3 6 7 5 4|7 6 4 5 1 2 3 0",
   .options = "",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_27 = {
@@ -82,6 +85,7 @@ static struct rcclRomeModel rome_model_27 = {
   .pattern = "11303011",
   .ringBase = "0 6 2 3 1 7 5 4|7 1 4 5 6 0 3 2",
   .options = "",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_29 = {
@@ -95,6 +99,7 @@ static struct rcclRomeModel rome_model_29 = {
   .pattern = "10302120",
   .ringBase = "6 5 7 4 0 1 3 2|6 4 7 5 2 3 1 0",
   .options = "",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_31 = {
@@ -108,6 +113,7 @@ static struct rcclRomeModel rome_model_31 = {
   .pattern = "0110201010200110",
   .ringBase = "1 2 3 0 6 4 5 7|4 6 7 5 2 1 0 3",
   .options = "",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_33 = {
@@ -121,6 +127,7 @@ static struct rcclRomeModel rome_model_33 = {
   .pattern = "0110201010200110",
   .ringBase = "1 4 5 7 0 3 2 6|4 1 7 5 6 2 3 0",
   .options = "",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_30 = {
@@ -134,6 +141,7 @@ static struct rcclRomeModel rome_model_30 = {
   .pattern = "0010201010200010",
   .ringBase = "3 0 1 2 6 7 5 4|2 1 0 3 7 6 4 5",
   .options = "",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_32 = {
@@ -147,6 +155,7 @@ static struct rcclRomeModel rome_model_32 = {
   .pattern = "0010201010200010",
   .ringBase = "0 6 2 3 4 5 7 1|3 2 6 0 1 7 5 4",
   .options = "",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_24 = {
@@ -160,6 +169,7 @@ static struct rcclRomeModel rome_model_24 = {
   .pattern = "10303010",
   .ringBase = "0 1 2 3 5 7 6 4|1 0 3 2 7 5 4 6",
   .options = "",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_26 = {
@@ -173,6 +183,7 @@ static struct rcclRomeModel rome_model_26 = {
   .pattern = "10303010",
   .ringBase = "4 5 7 1 0 3 2 6|3 0 6 2 1 7 5 4",
   .options = "",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_23 = {
@@ -186,6 +197,7 @@ static struct rcclRomeModel rome_model_23 = {
   .pattern = "10302020",
   .ringBase = "1 7 6 4 5 2 0 3|2 5 3 0 4 6 7 1",
   .options = "",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_38 = {
@@ -199,6 +211,7 @@ static struct rcclRomeModel rome_model_38 = {
   .pattern = "10201000201010",
   .ringBase = "6 7 1 4 3 5 2 0|0 2 5 3 4 1 7 6",
   .options = "",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_28 = {
@@ -212,6 +225,7 @@ static struct rcclRomeModel rome_model_28 = {
   .pattern = "10302020",
   .ringBase = "0 3 2 1 4 5 6 7|7 6 5 4 1 2 3 0|0 2 5 7 4 6 3 1|1 3 6 4 7 5 2 0",
   .options = "",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_40 = {
@@ -225,6 +239,7 @@ static struct rcclRomeModel rome_model_40 = {
   .pattern = "10302120",
   .ringBase = "6 7 1 4 0 5 3 2|7 6 4 1 0 2 3 5",
   .options = "",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_42 = {
@@ -238,6 +253,7 @@ static struct rcclRomeModel rome_model_42 = {
   .pattern = "10201001201010",
   .ringBase = "7 4 6 1 3 0 2 5|6 4 7 1 3 2 5 0",
   .options = "",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_44 = {
@@ -251,6 +267,7 @@ static struct rcclRomeModel rome_model_44 = {
   .pattern = "20202120",
   .ringBase = "5 4 7 6 2 1 3 0|5 6 7 4 1 0 2 3",
   .options = "",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_45 = {
@@ -264,6 +281,7 @@ static struct rcclRomeModel rome_model_45 = {
   .pattern = "10201000201010",
   .ringBase = "0 1 2 3 4 5 6 7|0 2 5 7 4 6 1 3|0 3 1 6 4 7 5 2|0 7 6 5 4 3 2 1",
   .options = "",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_46 = {
@@ -277,6 +295,7 @@ static struct rcclRomeModel rome_model_46 = {
   .pattern = "10201001201010",
   .ringBase = "6 5 7 4 1 2 3 0|7 4 6 5 1 0 3 2",
   .options = "",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_48 = {
@@ -290,6 +309,7 @@ static struct rcclRomeModel rome_model_48 = {
   .pattern = "20202020",
   .ringBase = "0 1 2 3 4 5 6 7|7 6 5 4 3 2 1 0|0 1 2 3 4 5 6 7|7 6 5 4 3 2 1 0",
   .options = "",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_49 = {
@@ -303,6 +323,7 @@ static struct rcclRomeModel rome_model_49 = {
   .pattern = "21212121",
   .ringBase = "N0 0 1 2 3 4 5 6 7 N3|N3 7 6 5 4 3 2 1 0 N0|N1 2 3 0 1 6 7 4 5 N2|N2 5 4 7 6 1 0 3 2 N1",
   .options = "",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_52 = {
@@ -316,6 +337,7 @@ static struct rcclRomeModel rome_model_52 = {
   .pattern = "80",
   .ringBase = "0 1 3 2 4 5 7 6|6 7 5 4 2 3 1 0|0 1 5 4 6 7 3 2|2 3 7 6 4 5 1 0",
   .options = "",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_53 = {
@@ -329,6 +351,7 @@ static struct rcclRomeModel rome_model_53 = {
   .pattern = "21212121",
   .ringBase = "N0 0 1 2 3 4 5 6 7 N3|N3 7 6 5 4 3 2 1 0 N0|N1 2 3 0 1 6 7 4 5 N2|N2 5 4 7 6 1 0 3 2 N1",
   .options = "",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_43 = {
@@ -342,6 +365,7 @@ static struct rcclRomeModel rome_model_43 = {
   .pattern = "20202020",
   .ringBase = "0 1 2 3 4 5 6 7|0 2 5 7 4 6 1 3|0 3 1 6 4 7 5 2|0 7 6 5 4 3 2 1",
   .options = "",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_55 = {
@@ -355,6 +379,7 @@ static struct rcclRomeModel rome_model_55 = {
   .pattern = "20202020",
   .ringBase = "0 1 2 3 4 5 6 7|7 6 5 4 3 2 1 0|2 3 0 1 6 7 4 5|5 4 7 6 1 0 3 2",
   .options = "",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_56 = {
@@ -368,6 +393,7 @@ static struct rcclRomeModel rome_model_56 = {
   .pattern = "40404040",
   .ringBase = "0 1 3 2 6 7 15 14 10 11 9 8 12 13 5 4|0 1 2 3 7 6 13 12 8 9 10 11 15 14 5 4|0 2 3 7 6 14 15 11 10 8 9 13 12 4 5 1|4 5 13 12 8 9 11 10 14 15 7 6 2 3 1 0|4 5 14 15 11 10 9 8 12 13 6 7 3 2 1 0|1 5 4 12 13 9 8 10 11 15 14 6 7 3 2 0",
   .options = "pivotA2AEnabled=1,pivotA2ANumBiRings=3,tuning=1",
+  .treeBase = "10 11|14 15|6 7|2 3|0 1|4 5|12 13|8 9",
 };
 
 static struct rcclRomeModel rome_model_58 = {
@@ -381,6 +407,7 @@ static struct rcclRomeModel rome_model_58 = {
   .pattern = "402020",
   .ringBase = "0 1 3 2 4 5 7 6|6 7 5 4 2 3 1 0|0 1 5 4 6 7 3 2|2 3 7 6 4 5 1 0",
   .options = "",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_59 = {
@@ -394,6 +421,7 @@ static struct rcclRomeModel rome_model_59 = {
   .pattern = "42424242",
   .ringBase = "N4 9 8 12 13 5 4 0 1 3 2 6 7 15 14 10 11 N5|N1 3 2 6 7 15 14 10 11 9 8 12 13 5 4 0 1 N0|N3 7 6 2 3 1 0 4 5 13 12 8 9 11 10 14 15 N7|N7 15 14 10 11 9 8 12 13 5 4 0 1 3 2 6 7 N3|N5 11 10 14 15 7 6 2 3 1 0 4 5 13 12 8 9 N4|N0 1 0 4 5 13 12 8 9 11 10 14 15 7 6 2 3 N1|N3 6 7 3 2 1 0 4 5 14 15 11 10 9 8 12 13 N6|N7 14 15 11 10 9 8 12 13 6 7 3 2 1 0 4 5 N2|N2 5 4 0 1 2 3 7 6 13 12 8 9 10 11 15 14 N7|N6 13 12 8 9 10 11 15 14 5 4 0 1 2 3 7 6 N3|N4 8 9 13 12 4 5 1 0 2 3 7 6 14 15 11 10 N5|N5 10 11 15 14 6 7 3 2 0 1 5 4 12 13 9 8 N4|N6 12 13 9 8 10 11 15 14 6 7 3 2 0 1 5 4 N2|N2 4 5 1 0 2 3 7 6 14 15 11 10 8 9 13 12 N6|N1 2 3 7 6 14 15 11 10 8 9 13 12 4 5 1 0 N0|N0 0 1 5 4 12 13 9 8 10 11 15 14 6 7 3 2 N1|N5 10 11 9 8 12 13 5 4 0 1 3 2 6 7 15 14 N7|N3 6 7 15 14 10 11 9 8 12 13 5 4 0 1 3 2 N1|N1 2 3 1 0 4 5 13 12 8 9 11 10 14 15 7 6 N3|N7 14 15 7 6 2 3 1 0 4 5 13 12 8 9 11 10 N5|N0 0 1 2 3 7 6 13 12 8 9 10 11 15 14 5 4 N2|N4 8 9 10 11 15 14 5 4 0 1 2 3 7 6 13 12 N6|N3 7 6 13 12 8 9 10 11 15 14 5 4 0 1 2 3 N1|N1 3 2 1 0 4 5 14 15 11 10 9 8 12 13 6 7 N3|N6 12 13 6 7 3 2 1 0 4 5 14 15 11 10 9 8 N4|N2 4 5 14 15 11 10 9 8 12 13 6 7 3 2 1 0 N0|N0 1 0 2 3 7 6 14 15 11 10 8 9 13 12 4 5 N2|N6 13 12 4 5 1 0 2 3 7 6 14 15 11 10 8 9 N4|N5 11 10 8 9 13 12 4 5 1 0 2 3 7 6 14 15 N7|N2 5 4 12 13 9 8 10 11 15 14 6 7 3 2 0 1 N0|N7 15 14 6 7 3 2 0 1 5 4 12 13 9 8 10 11 N5|N4 9 8 10 11 15 14 6 7 3 2 0 1 5 4 12 13 N6",
   .options = "tuning=1",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_62 = {
@@ -407,6 +435,7 @@ static struct rcclRomeModel rome_model_62 = {
   .pattern = "20202020",
   .ringBase = "0 1 3 2 4 5 7 6|6 7 5 4 2 3 1 0|0 1 5 4 6 7 3 2|2 3 7 6 4 5 1 0",
   .options = "",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_63 = {
@@ -420,6 +449,7 @@ static struct rcclRomeModel rome_model_63 = {
   .pattern = "21212121",
   .ringBase = "N0 0 1 5 4 6 7 3 2 N1|N1 2 3 7 6 4 5 1 0 N0|N3 7 6 0 1 3 2 4 5 N2|N2 5 4 2 3 1 0 6 7 N3|N0 0 1 5 4 6 7 3 2 N1|N1 2 3 7 6 4 5 1 0 N0|N3 7 6 0 1 3 2 4 5 N2|N2 5 4 2 3 1 0 6 7 N3",
   .options = "tuning=3",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_65 = {
@@ -433,6 +463,7 @@ static struct rcclRomeModel rome_model_65 = {
   .pattern = "42424242",
   .ringBase = "N4 9 8 12 13 5 4 0 1 3 2 6 7 15 14 10 11 N5|N1 3 2 6 7 15 14 10 11 9 8 12 13 5 4 0 1 N0|N3 7 6 2 3 1 0 4 5 13 12 8 9 11 10 14 15 N7|N7 15 14 10 11 9 8 12 13 5 4 0 1 3 2 6 7 N3|N5 11 10 14 15 7 6 2 3 1 0 4 5 13 12 8 9 N4|N0 1 0 4 5 13 12 8 9 11 10 14 15 7 6 2 3 N1|N3 6 7 3 2 1 0 4 5 14 15 11 10 9 8 12 13 N6|N7 14 15 11 10 9 8 12 13 6 7 3 2 1 0 4 5 N2|N2 5 4 0 1 2 3 7 6 13 12 8 9 10 11 15 14 N7|N6 13 12 8 9 10 11 15 14 5 4 0 1 2 3 7 6 N3|N4 8 9 13 12 4 5 1 0 2 3 7 6 14 15 11 10 N5|N5 10 11 15 14 6 7 3 2 0 1 5 4 12 13 9 8 N4|N6 12 13 9 8 10 11 15 14 6 7 3 2 0 1 5 4 N2|N2 4 5 1 0 2 3 7 6 14 15 11 10 8 9 13 12 N6|N1 2 3 7 6 14 15 11 10 8 9 13 12 4 5 1 0 N0|N0 0 1 5 4 12 13 9 8 10 11 15 14 6 7 3 2 N1|N5 10 11 9 8 12 13 5 4 0 1 3 2 6 7 15 14 N7|N3 6 7 15 14 10 11 9 8 12 13 5 4 0 1 3 2 N1|N1 2 3 1 0 4 5 13 12 8 9 11 10 14 15 7 6 N3|N7 14 15 7 6 2 3 1 0 4 5 13 12 8 9 11 10 N5|N0 0 1 2 3 7 6 13 12 8 9 10 11 15 14 5 4 N2|N4 8 9 10 11 15 14 5 4 0 1 2 3 7 6 13 12 N6|N3 7 6 13 12 8 9 10 11 15 14 5 4 0 1 2 3 N1|N1 3 2 1 0 4 5 14 15 11 10 9 8 12 13 6 7 N3|N6 12 13 6 7 3 2 1 0 4 5 14 15 11 10 9 8 N4|N2 4 5 14 15 11 10 9 8 12 13 6 7 3 2 1 0 N0|N0 1 0 2 3 7 6 14 15 11 10 8 9 13 12 4 5 N2|N6 13 12 4 5 1 0 2 3 7 6 14 15 11 10 8 9 N4|N5 11 10 8 9 13 12 4 5 1 0 2 3 7 6 14 15 N7|N2 5 4 12 13 9 8 10 11 15 14 6 7 3 2 0 1 N0|N7 15 14 6 7 3 2 0 1 5 4 12 13 9 8 10 11 N5|N4 9 8 10 11 15 14 6 7 3 2 0 1 5 4 12 13 N6",
   .options = "netGdrLevel=PHB,tuning=4",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_66 = {
@@ -446,6 +477,7 @@ static struct rcclRomeModel rome_model_66 = {
   .pattern = "4040",
   .ringBase = "0 6 7 5 4 2 3 1|1 3 2 4 5 7 6 0|0 1 7 6 2 3 5 4|4 5 3 2 6 7 1 0",
   .options = "disableNumaMatching=1,tuning=2",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_67 = {
@@ -459,6 +491,7 @@ static struct rcclRomeModel rome_model_67 = {
   .pattern = "4242",
   .ringBase = "N3 7 6 0 1 3 2 4 5 N2|N2 5 4 2 3 1 0 6 7 N3|N1 2 3 5 4 0 1 7 6 N3|N2 4 5 3 2 6 7 1 0 N0|N1 3 2 4 5 7 6 0 1 N0|N0 1 0 6 7 5 4 2 3 N1|N0 0 1 7 6 2 3 5 4 N2|N3 6 7 1 0 4 5 3 2 N1",
   .options = "disableNumaMatching=1,tuning=2",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_68 = {
@@ -472,6 +505,7 @@ static struct rcclRomeModel rome_model_68 = {
   .pattern = "@@",
   .ringBase = "N0 0 1 2 3 N3 N4 4 5 6 7 N7 N8 8 9 10 11 N11 N12 12 13 14 15 N15|N15 15 14 13 12 N12 N11 11 10 9 8 N8 N7 7 6 5 4 N4 N3 3 2 1 0 N0|N1 1 3 0 2 N2 N5 5 7 4 6 N6 N9 9 11 8 10 N10 N13 13 15 12 14 N14|N14 14 12 15 13 N13 N10 10 8 11 9 N9 N6 6 4 7 5 N5 N2 2 0 3 1 N1|N0 0 1 2 3 N3 N4 4 5 6 7 N7 N8 8 9 10 11 N11 N12 12 13 14 15 N15|N15 15 14 13 12 N12 N11 11 10 9 8 N8 N7 7 6 5 4 N4 N3 3 2 1 0 N0|N1 1 3 0 2 N2 N5 5 7 4 6 N6 N9 9 11 8 10 N10 N13 13 15 12 14 N14|N14 14 12 15 13 N13 N10 10 8 11 9 N9 N6 6 4 7 5 N5 N2 2 0 3 1 N1",
   .options = "netGdrLevel=PIX",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_71 = {
@@ -485,6 +519,7 @@ static struct rcclRomeModel rome_model_71 = {
   .pattern = "4040",
   .ringBase = "0 1 3 2 4 5 7 6|6 7 5 4 2 3 1 0|0 1 5 4 2 3 7 6|6 7 3 2 4 5 1 0",
   .options = "disableNumaMatching=1,tuning=2",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_72 = {
@@ -498,6 +533,7 @@ static struct rcclRomeModel rome_model_72 = {
   .pattern = "4242",
   .ringBase = "N0 0 1 3 2 4 5 7 6 N3|N1 2 3 1 0 6 7 5 4 N2|N3 7 6 0 1 5 4 2 3 N1|N0 1 0 6 7 3 2 4 5 N2|N2 4 5 7 6 0 1 3 2 N1|N3 6 7 5 4 2 3 1 0 N0|N2 5 4 2 3 7 6 0 1 N0|N1 3 2 4 5 1 0 6 7 N3",
   .options = "disableNumaMatching=1,tuning=2",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_73 = {
@@ -511,6 +547,7 @@ static struct rcclRomeModel rome_model_73 = {
   .pattern = "20202020",
   .ringBase = "0 1 3 2 4 5 7 6|6 7 5 4 2 3 1 0|0 1 5 4 6 7 3 2|2 3 7 6 4 5 1 0",
   .options = "",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel rome_model_74 = {
@@ -524,6 +561,7 @@ static struct rcclRomeModel rome_model_74 = {
   .pattern = "21212121",
   .ringBase = "N0 0 1 5 4 6 7 3 2 N1|N1 2 3 7 6 4 5 1 0 N0|N3 7 6 0 1 3 2 4 5 N2|N2 5 4 2 3 1 0 6 7 N3|N0 0 1 5 4 6 7 3 2 N1|N1 2 3 7 6 4 5 1 0 N0|N3 7 6 0 1 3 2 4 5 N2|N2 5 4 2 3 1 0 6 7 N3",
   .options = "tuning=3",
+  .treeBase = "",
 };
 
 static struct rcclRomeModel romeTopoModels[] = {
@@ -681,6 +719,75 @@ end:
   return ncclSuccess;
 }
 
+
+/* Parse user defined treeBase for complicated trees. Format is like :
+ * "10 11|14 15|6 7|2 3|0 1|4 5|12 13|8 9"
+ *
+ * Rings with a non-matching number of gpus are ignored so we can provide
+ * rings for multiple cases.
+ */
+ncclResult_t parseGraphLight(const char* str, struct ncclTopoSystem* system, struct ncclTopoGraph* graph, int* gpu_map) {
+  int gpus[NCCL_TOPO_MAX_NODES];
+  int nChannels = 0;
+  int gpu = 0;
+  int offset = 0;
+  if (str[0] == 0) return ncclSuccess;
+  int status = 0; // 0 : between numbers, 1 : inside number, 2: start NET, 3: inside NET
+  int nets[NCCL_TOPO_MAX_NODES*2];
+  int net_offset = 0, net_count = 0;
+  int ngpus = system->nodes[GPU].count;
+  // int nnets = system->nodes[NET].count;
+  int x=0, y=0;
+  // |
+  // from | to | x to y
+  do {
+    int digit = str[offset] - '0';
+    if (digit >= 0 && digit <= 9) {
+      // offset++; // all the offsets
+      switch (status) {
+        case 0:
+          gpus[gpu] = digit;
+          status = 1;
+          break;
+        case 1:
+          gpus[gpu] = gpus[gpu]*10+digit;
+          break;
+      }
+    } else {
+      if (status == 1) {
+        gpu++;
+      }
+      status = 0;
+      if (str[offset] == '|' || str[offset] == 0) { // bump y, and x and make x 0 after
+        for (int r=0; r<gpu; r++) {
+          int g = gpus[r];
+          // remap if needed
+          if (gpu_map) g = gpu_map[g];
+          // Translate gpu numbers into ranks
+          int j = 0;
+          for (j = 0; j < ngpus; j++)
+            if (g == system->nodes[GPU].nodes[j].gpu.dev)
+              break;
+          if (j < ngpus)
+          {
+            graph->treeBase[r][x] = system->nodes[GPU].nodes[j].gpu.rank;
+            y=r;
+          }
+          else
+            return ncclInternalError;
+        }
+        y++;
+        graph->treeBase[y][x] = -1;
+        // y=0;
+        x++;
+        gpu=0;
+      }
+    }
+  } while (str[offset++] != 0);
+  graph->treeBase[0][x] = -1;
+  return ncclSuccess;
+}
+
 #define MAX_OPT_TOKENS 10
 extern const char* topoPathTypeStr[];
 
@@ -1274,6 +1381,8 @@ ncclResult_t parse1H16P(struct ncclTopoSystem* system, struct ncclTopoGraph* gra
 
   // create 16P1H based on reference and remapped ids
   NCCLCHECK(parseGraph(romeTopoModels[i].ringBase, system, graph, g16, nnets > 1 ? n : NULL));
+
+  NCCLCHECK(parseGraphLight(romeTopoModels[i].treeBase, system, graph, g16));
   // clean up
   free(all_gpu_permutations);
   return ncclSuccess;
diff --git a/src/graph/tuning.cc b/src/graph/tuning.cc
index 137386197a..259bb8a4bd 100644
--- a/src/graph/tuning.cc
+++ b/src/graph/tuning.cc
@@ -281,7 +281,8 @@ ncclResult_t ncclTopoTuneModel(struct ncclComm* comm, int minCompCap, int maxCom
       nNodes;
 
     for (int a=0; a<NCCL_NUM_ALGORITHMS; a++) {
-      if ((coll != ncclFuncAllReduce || nNodes == 1) && a != NCCL_ALGO_RING) continue;
+      // if ((coll != ncclFuncAllReduce || nNodes == 1) && a != NCCL_ALGO_RING) continue;
+      if ((coll != ncclFuncAllReduce) && a != NCCL_ALGO_RING) continue;
 
       for (int p=0; p<NCCL_NUM_PROTOCOLS; p++) {
         float speed = nNodes <= 2 || a == NCCL_ALGO_COLLNET ? graphs[a]->speedIntra : graphs[a]->speedInter;
diff --git a/src/include/graph.h b/src/include/graph.h
index 4cfe9539a6..57727eef84 100644
--- a/src/include/graph.h
+++ b/src/include/graph.h
@@ -89,6 +89,7 @@ struct ncclTopoGraph {
   int inter[MAXCHANNELS*2];
   int nIntraChannels;
   int intraNets[MAXCHANNELS*NCCL_TOPO_MAX_NODES*2];
+  int treeBase[NCCL_TOPO_MAX_NODES][NCCL_TOPO_MAX_NODES];
 };
 ncclResult_t ncclTopoCompute(struct ncclTopoSystem* system, struct ncclTopoGraph* graph);
 
@@ -112,6 +113,8 @@ ncclResult_t ncclTopoPreset(struct ncclComm* comm,
 ncclResult_t ncclTopoPostset(struct ncclComm* comm, int* firstRanks, int* treePatterns,
     struct ncclTopoRanks** allTopoRanks, int* rings, struct ncclTopoGraph* collNetGraph, int nc);
 
+ncclResult_t ncclTreeBasePostset(struct ncclComm* comm, struct ncclTopoGraph* treeGraph);
+
 ncclResult_t ncclTopoTuneModel(struct ncclComm* comm, int minCompCap, int maxCompCap, struct ncclTopoGraph* treeGraph, struct ncclTopoGraph* ringGraph, struct ncclTopoGraph* collNetGraph);
 #include "info.h"
 ncclResult_t ncclTopoGetAlgoTime(struct ncclInfo* info, int algorithm, int protocol, int numPipeOps, float* time);
diff --git a/src/init.cc b/src/init.cc
index 557c440afc..fbbcf2ae34 100644
--- a/src/init.cc
+++ b/src/init.cc
@@ -1002,6 +1002,8 @@ static ncclResult_t initTransportsRank(struct ncclComm* comm, ncclUniqueId* comm
   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);
@@ -1017,7 +1019,7 @@ static ncclResult_t initTransportsRank(struct ncclComm* comm, ncclUniqueId* comm
     struct ncclTree* tree = &comm->channels[c].tree;
     snprintf(line+strlen(line), 1023-strlen(line), " [%d] %d/%d/%d->%d->%d",
         c, tree->down[0], tree->down[1], tree->down[2], rank, tree->up);
-    INFO(NCCL_GRAPH, "Ring %d : %d -> %d -> %d comm %p nRanks %02d busId %lx", c, comm->channels[c].ring.prev, 
+    INFO(NCCL_GRAPH, "Ring %d : %d -> %d -> %d comm %p nRanks %02d busId %lx", c, comm->channels[c].ring.prev,
          comm->rank, comm->channels[c].ring.next, comm, comm->nRanks, comm->busId);
   }
   line[1023] = '\0';
diff --git a/tools/topo_expl/utils.cpp b/tools/topo_expl/utils.cpp
index 42f93cad02..d70d7a7021 100644
--- a/tools/topo_expl/utils.cpp
+++ b/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);