From cdae05b27728b1b5b25b3a4f294334df9fb5164d Mon Sep 17 00:00:00 2001
From: Sylvain Jeaugey <sjeaugey@nvidia.com>
Date: Tue, 4 Dec 2018 11:57:35 -0800
Subject: [PATCH] Improve INFO message when external network is not found.

Fix #162
---
 src/init.cu | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/src/init.cu b/src/init.cu
index c9700a8..a8c8011 100644
--- a/src/init.cu
+++ b/src/init.cu
@@ -86,7 +86,14 @@ ncclResult_t initNet(ncclNet_t* net) {
 ncclResult_t initNetPlugin(ncclNet_t** net) {
   void* netPluginLib = dlopen("libnccl-net.so", RTLD_NOW | RTLD_LOCAL);
   if (netPluginLib == NULL) {
-    INFO(NCCL_INIT, "Unable to load libnccl-net.so : %s", dlerror());
+    // dlopen does not guarantee to set errno, but dlerror only gives us a
+    // string, so checking errno doesn't hurt to try to provide a better
+    // error message
+    if (errno == ENOENT) {
+      INFO(NCCL_INIT, "No network plugin found.");
+    } else {
+      INFO(NCCL_INIT, "Unable to load libnccl-net.so : %s", dlerror());
+    }
     return ncclSuccess;
   }
   ncclNet_t* extNet = (ncclNet_t*) dlsym(netPluginLib, STR(NCCL_PLUGIN_SYMBOL));
@@ -109,7 +116,7 @@ ncclResult_t initNet() {
 
   NCCLCHECK(initNetPlugin(&ncclNet));
   if (ncclNet != NULL) {
-    INFO(NCCL_INIT, "Using external Network %s", ncclNetName());
+    INFO(NCCL_INIT, "Using network plugin %s", ncclNetName());
     return ncclSuccess;
   }
   if (initNet(&ncclNetIb) == ncclSuccess) {
@@ -117,7 +124,7 @@ ncclResult_t initNet() {
   } else {
     ncclNet = &ncclNetSocket;
   }
-  INFO(NCCL_INIT,"Using internal Network %s", ncclNetName());
+  INFO(NCCL_INIT,"Using network %s", ncclNetName());
   return ncclSuccess;
 }