From 1d989f65249c3cb602a64cce1dd666464dc058ad Mon Sep 17 00:00:00 2001
From: Wenkai Du <43822138+wenkaidu@users.noreply.github.com>
Date: Fri, 2 Feb 2024 12:41:00 -0800
Subject: [PATCH] Doubling P2P channels per peer on single node only (#1069)

---
 src/graph/paths.cc | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/graph/paths.cc b/src/graph/paths.cc
index 4180f3e660..bb1e33a1c0 100644
--- a/src/graph/paths.cc
+++ b/src/graph/paths.cc
@@ -861,7 +861,8 @@ ncclResult_t ncclTopoComputeP2pChannels(struct ncclComm* comm) {
   } else {
     // Round to next pow2 nChannelsPerPeer and nChannels
     comm->p2pnChannelsPerPeer = (ncclParamNChannelsPerPeer() == -2 ? nextPow2(minChannels) : ncclParamNChannelsPerPeer());
-    comm->p2pnChannelsPerPeer *= 2;
+    // Doubling P2P channels per peer on single node
+    if (comm->topo->nodes[GPU].count == comm->topo->nRanks) comm->p2pnChannelsPerPeer *= 2;
     comm->p2pnChannels = nextPow2(comm->p2pnChannels);
   }