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separate comm init from getXCClComm #2090

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separate comm init from getXCClComm #2090

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08de734
separate comm init from getXCClComm
Chao1Han Sep 22, 2025
284e3db
Update src/xccl/ProcessGroupXCCL.cpp
Chao1Han Oct 9, 2025
2e56dcd
Merge branch 'main' into xccl/comm
mengfei25 Oct 9, 2025
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28 changes: 19 additions & 9 deletions src/xccl/ProcessGroupXCCL.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -491,6 +491,17 @@ c10::intrusive_ptr<ProcessGroupXCCL::WorkXCCL> ProcessGroupXCCL::initWork(
}

std::shared_ptr<xcclComm_t> ProcessGroupXCCL::getXCCLComm(
const std::string& deviceKey) {
std::lock_guard<std::mutex> lock(mutex_);
auto it = devXCCLCommMap_.find(deviceKey);
if (it != devXCCLCommMap_.end()) {
// Reuse the cached communicator if there is one.
return it->second;
}
return nullptr;
}

std::shared_ptr<xcclComm_t> ProcessGroupXCCL::initXCCLComm(
const std::string& deviceKey,
at::Device& device,
OpType opType,
Expand All @@ -505,13 +516,6 @@ std::shared_ptr<xcclComm_t> ProcessGroupXCCL::getXCCLComm(

usedDeviceIdxs_.insert(device.index());

{
std::lock_guard<std::mutex> lock(mutex_);
if (devXCCLCommMap_.find(deviceKey) != devXCCLCommMap_.end()) {
return devXCCLCommMap_[deviceKey];
}
}

std::shared_ptr<xcclComm_t> XCCLComm;

bool batchP2P = xcclActiveGroupCounter_ > 0;
Expand Down Expand Up @@ -669,7 +673,10 @@ c10::intrusive_ptr<Work> ProcessGroupXCCL::collective(
nanCheck &= enableNanCheck_;
auto device = inputs[0].device();
const auto key = std::to_string(device.index());
auto comm = getXCCLComm(key, device, opType);
std::shared_ptr<xcclComm_t> comm = getXCCLComm(key);
if (comm == nullptr) {
comm = initXCCLComm(key, device, opType);
}

if (!coalescing_state_) {
seqCollective_++;
Expand Down Expand Up @@ -835,7 +842,10 @@ c10::intrusive_ptr<Work> ProcessGroupXCCL::pointToPoint(
}

op_id_++;
auto comm = getXCCLComm(key, device, opType, p2pRank, isSendRecvSelf);
std::shared_ptr<xcclComm_t> comm = getXCCLComm(key);
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Seems like no difference with previous code, then why to separate as two APIs/steps?

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Just for align nccl, To facilitate future feature integration, we can first align this part.

if (comm == nullptr) {
comm = initXCCLComm(key, device, opType, p2pRank, isSendRecvSelf);
}

if (coalescing_state_ & CoalActive) {
if ((coalescing_state_ & CoalP2P) == 0) {
Expand Down
4 changes: 3 additions & 1 deletion src/xccl/ProcessGroupXCCL.hpp
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Expand Up @@ -166,7 +166,9 @@ class TORCH_API ProcessGroupXCCL : public Backend {

c10::intrusive_ptr<Work> endCoalescing(OpType optype);

std::shared_ptr<xcclComm_t> getXCCLComm(
std::shared_ptr<xcclComm_t> getXCCLComm(const std::string& deviceKey);

std::shared_ptr<xcclComm_t> initXCCLComm(
const std::string& deviceKey,
at::Device& device,
OpType opType,
Expand Down
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