Function ncclCommInitRankConfig 

pub unsafe extern "C" fn ncclCommInitRankConfig(
    comm: *mut NcclComm,
    nranks: i32,
    id: NcclUniqueId,
    rank: i32,
    config: *const NcclConfig,
) -> NcclResult

Non-blocking variant: set config.blocking=0 so ncclGroupEnd returns immediately. Poll ncclCommGetAsyncError to check completion and detect hangs with timeout.