NVIDIA Deep Learning NCCL Documentation
Release Notes (PDF) - v2.21.5 - Last updated April 5, 2024

NCCL Release 2.15.5

This is the NCCL 2.15.5 release notes. For previous NCCL release notes, refer to the NCCL Archives.


NCCL 2.15.5 has been tested with the following:

Fixed Issues

The following issues have been resolved in NCCL 2.15.5:

  • Fix crash with CollnetChain on some node topologies

  • Fix hang when interleaving the capture of different graphs

  • Fix hang during init in multi-threaded mode

  • Fix potential data corruption with LL128 protocol on unaligned buffers

  • Fix CPU usage during preconnect

  • Fixes double-free in the error path for ncclCommInitAll

  • Workaround hang on H100 with Ring/LL128 on 2 GPUs

Updating the GPG Repository Key

To best ensure the security and reliability of our RPM and Debian package repositories, NVIDIA is updating and rotating the signing keys used by apt, dnf/yum, and zypper package managers beginning on April 27, 2022. Failure to update your repository signing keys will result in package management errors when attempting to access or install NCCL packages. To ensure continued access to the latest NCCL release, please follow the updated NCCL installation guide.