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ctran: enable per-block flag for broadcast with tcpdm/unpack #2079

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ctran: enable per-block flag for broadcast with tcpdm/unpack #2079

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aa1eb3b
tcp_devmem: bring back ncclx conda support for v2.29
Apr 14, 2026
ab6a995
ctran: enable per-block flag for broadcast with tcpdm/unpack
Apr 15, 2026
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32 changes: 25 additions & 7 deletions comms/ctran/algos/Broadcast/Broadcast.cu
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Original file line number Diff line number Diff line change
Expand Up @@ -22,16 +22,28 @@ __global__ void __launch_bounds__(1024, 1) ncclKernelBroadcast(
ctran::broadcast::KernelArgs args) {
const auto gtIdx = blockDim.x * blockIdx.x + threadIdx.x;

if (flag && gtIdx == 0) {
ctran::device::devLoadAbortFlags(flag, devState);
ctran::device::KernelStartGpe(flag);
if (UNPACK) {
// Per-block flag management (matches SendRecv pattern) to avoid race
// where block 0 clears the shared flag before other blocks exit waitUnpack.
if (flag && threadIdx.x == 0) {
ctran::device::KernelStartGpe(&flag[blockIdx.x]);
}
devStateLoadToShm(&flag[blockIdx.x], devState);
} else {
if (flag && gtIdx == 0) {
ctran::device::devLoadAbortFlags(flag, devState);
ctran::device::KernelStartGpe(flag);
}
devStateLoadToShm(devState);
}

devStateLoadToShm(devState);
#ifndef CTRAN_DISABLE_TCPDM
if (UNPACK) {
waitUnpack(
args.unpack.sq[blockIdx.x], &broadcastUnpack, flag, KERNEL_TERMINATE);
args.unpack.sq[blockIdx.x],
&broadcastUnpack,
&flag[blockIdx.x],
KERNEL_TERMINATE);
}
#endif

Expand All @@ -49,8 +61,14 @@ __global__ void __launch_bounds__(1024, 1) ncclKernelBroadcast(
args.putNotifyList);
}

if (flag && gtIdx == 0) {
ctran::device::KernelWaitGpeTerminate(flag);
if (UNPACK) {
if (flag && threadIdx.x == 0) {
ctran::device::KernelWaitGpeTerminate(&flag[blockIdx.x]);
}
} else {
if (flag && gtIdx == 0) {
ctran::device::KernelWaitGpeTerminate(flag);
}
}
}

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1 change: 1 addition & 0 deletions comms/ctran/gpe/CtranGpeImpl.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -276,6 +276,7 @@ commResult_t CtranGpe::Impl::submit(
KernelConfig::KernelType::SENDRECV,
KernelConfig::KernelType::RECV_UNPACK,
KernelConfig::KernelType::SENDRECV_UNPACK,
KernelConfig::KernelType::BROADCAST_UNPACK,
};
if (perBlockFlagEnabledKernels.contains(kernelConfig.type)) {
kernelFlag->numGroups_ = kernelConfig.numBlocks;
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