2.20.3-1

Add support for alternating rings, allow for cross-nic rings without
cross-rail communication.
Add support for user buffer registration for network send/recv.
Optimize aggregated operations to better utilize all channels.
Add flattening for BCM PCI gen5 switches.
Add support for inter-node NVLink communication
Add support for port fusion in NET/IB.
Add support for ReduceScatter and AllGather using Collnet.
Update net API to v8.
Fix hang during A2A connection.

src/debug.cc

@@ -191,6 +191,9 @@ void ncclDebugLog(ncclDebugLogLevel level, unsigned long flags, const char *file
     va_start(vargs, fmt);
     len += vsnprintf(buffer+len, sizeof(buffer)-len, fmt, vargs);
     va_end(vargs);
+    // vsnprintf may return len > sizeof(buffer) in the case of a truncated output.
+    // Rewind len so that we can replace the final \0 by \n
+    if (len > sizeof(buffer)) len = sizeof(buffer)-1;
     buffer[len++] = '\n';
     fwrite(buffer, 1, len, ncclDebugFile);
   }