Issues

• NCCL Roadmap: Nov 2026 - Jan 2027

  roadmap
  NVIDIA/nccl#2486 · Filter by author gab9talavera opened on Oct 16, 2026

• [Issue]: A failed thread creation aborts the process (std::terminate) instead of returning ncclSystemError

  NVIDIA/nccl#2484 · Filter by author kodlan opened on Oct 15, 2026
  

• [Issue]: GIN GDAKI: a failed put is invisible to device code (flush returns, get data never arrives), and the host learns of it once, at the 10 s query

  NVIDIA/nccl#2483 · Filter by author unionxic opened on Oct 15, 2026

• [Issue]: GIN GDAKI: NCCL_GIN_GDAKI_NIC_HANDLER=6 is accepted at init, but GIN operations never complete

  NVIDIA/nccl#2480 · Filter by author unionxic opened on Oct 15, 2026
  1

  

• [Issue]: BF16/FP16 NVLS AllReduce and ReduceScatter are not repeatable when count % 4 != 0

  NVIDIA/nccl#2479 · Filter by author qcliao opened on Oct 14, 2026
  2

  

• [Question]: How much benefit can NcclCommRegister provide？

  question
  NVIDIA/nccl#2476 · Filter by author ZhouMinhao98 opened on Oct 13, 2026
  3

  

• [Issue]: Early error returns inside an internal group leave the thread stuck one group level deep (later work never launches)

  NVIDIA/nccl#2471 · Filter by author kodlan opened on Oct 11, 2026
  

• [Issue]: bootstrapCreateRoot leaks the socket descriptor when ncclSocketListen fails, so each ncclGetUniqueId that fails in bind() leaks one fd

  NVIDIA/nccl#2469 · Filter by author dmvevents opened on Oct 10, 2026
  4

  

• [Issue]: GIN defaults to GDAKI on HCAs the NET plugin doesn't use, and the per-rank fallback deadlocks DevComm setup

  NVIDIA/nccl#2468 · Filter by author Oseltamivir opened on Oct 9, 2026
  3

  

• [Issue]: More inline data than it reserved space for, when receives get grouped

  NVIDIA/nccl#2467 · Filter by author jeseszhang1010 opened on Oct 9, 2026
  2

  

• [RFE]: AMD SYS-path restriction may limit ring diversity and AllReduce performance on multi-socket PCIe GPU systems

  enhancement
  NVIDIA/nccl#2466 · Filter by author Y7cc opened on Oct 9, 2026

• [Issue]: P2P operations fail at first call with NCCL_NET_GDR_READ=0 when PXN is selected

  NVIDIA/nccl#2463 · Filter by author lsavers opened on Oct 7, 2026
  2

  

• [Issue]: Collectives and send/recv on a suspended communicator (ncclCommSuspend) are accepted and crash instead of returning an error

  NVIDIA/nccl#2461 · Filter by author kodlan opened on Oct 6, 2026
  1

  

• [Issue]: ncclCommShrink with an invalid excludeRanksList (nonexistent, negative or duplicate rank) aborts the parent communicator instead of returning ncclInvalidArgument

  NVIDIA/nccl#2457 · Filter by author kodlan opened on Oct 1, 2026
  2

  

• [Question]: Fluctuating performance of GIN puts from a hybrid GIN+LSA device kernel

  question
  NVIDIA/nccl#2454 · Filter by author parinayc20 opened on Sep 29, 2026
  5

  

• [Issue]: ncclCommInitRankConfig / ncclCommInitRankScalable / ncclCommInitAll crash on invalid nranks, nId or ndev instead of returning ncclInvalidArgument

  NVIDIA/nccl#2449 · Filter by author kodlan opened on Sep 26, 2026
  1

  

• [Issue]: ncclAllReduce with ncclAvg on symmetric-memory buffers fails with "unhandled cuda error" (no avg AllReduce symmetric kernels, but ncclSymkImplemented says there are)

  NVIDIA/nccl#2447 · Filter by author kodlan opened on Sep 25, 2026
  1

  

• [Issue]: p8 sum AllReduce over symmetric memory crashes on sm_120 (RTX 5070 Ti) with CUDA 12.8 - 13.0: ptxas drops the upper 32 bits of the LL buffer address

  NVIDIA/nccl#2445 · Filter by author kodlan opened on Sep 24, 2026
  2

  

• [Issue]:wrap_ibv_reg_mr_iova2(NULL, NULL, NULL, 0, 0, 0); segment fault

  NVIDIA/nccl#2444 · Filter by author shenhongqian opened on Sep 24, 2026
  4

  

• [RFE]: is_all_reduce_fp32_accumulate_enabled (NVL OR symmetric memory)

  enhancement
  NVIDIA/nccl#2442 · Filter by author stas00 opened on Sep 23, 2026
  1

  

• [Issue]: Performance drop 60% in all_reduce_perf 1MB size on AMD CPU

  NVIDIA/nccl#2441 · Filter by author codambro opened on Sep 22, 2026
  13

  

• [Bug] NVLS: parent comm hits illegal memory access when a splitShare child with fewer NVLS channels runs NVLS first

  NVIDIA/nccl#2430 · Filter by author LiRunGuo opened on Sep 21, 2026
  1

  

• [Question] NCCL_IGNORE_NET_MISMATCH turns a heterogeneous-HCA misconfiguration into a silent hang

  resolved
  NVIDIA/nccl#2428 · Filter by author luoyuctl opened on Sep 21, 2026
  13

  

• ncclAlltoAllConfig does not honor per-call maxCTAs

  NVIDIA/nccl#2421 · Filter by author ngoyal2707 opened on Sep 18, 2026
  2

  

• NVCC_GENCODE_LDMC_FP8 device-code gencode ignores the caller's NVCC_GENCODE target-arch list, breaking single-arch builds

  NVIDIA/nccl#2420 · Filter by author zbrad opened on Sep 18, 2026
  2