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lightgbm-org--lightgbm/src/network/network.cpp
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2026-07-13 13:27:18 +08:00

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/*!
* Copyright (c) 2016-2026 Microsoft Corporation. All rights reserved.
* Copyright (c) 2016-2026 The LightGBM developers. All rights reserved.
* Licensed under the MIT License. See LICENSE file in the project root for license information.
*/
#include <LightGBM/network.h>
#include <LightGBM/utils/common.h>
#include <algorithm>
#include <cstdlib>
#include <cstring>
#include <memory>
#include <vector>
#include "linkers.h"
namespace LightGBM {
// static member definition
THREAD_LOCAL int Network::num_machines_ = 1;
THREAD_LOCAL int Network::rank_ = 0;
THREAD_LOCAL std::unique_ptr<Linkers> Network::linkers_;
THREAD_LOCAL BruckMap Network::bruck_map_;
THREAD_LOCAL RecursiveHalvingMap Network::recursive_halving_map_;
THREAD_LOCAL std::vector<comm_size_t> Network::block_start_;
THREAD_LOCAL std::vector<comm_size_t> Network::block_len_;
THREAD_LOCAL comm_size_t Network::buffer_size_ = 0;
THREAD_LOCAL std::vector<char> Network::buffer_;
THREAD_LOCAL ReduceScatterFunction Network::reduce_scatter_ext_fun_ = nullptr;
THREAD_LOCAL AllgatherFunction Network::allgather_ext_fun_ = nullptr;
void Network::Init(Config config) {
if (config.num_machines > 1) {
linkers_.reset(new Linkers(config));
rank_ = linkers_->rank();
num_machines_ = linkers_->num_machines();
bruck_map_ = linkers_->bruck_map();
recursive_halving_map_ = linkers_->recursive_halving_map();
block_start_ = std::vector<comm_size_t>(num_machines_);
block_len_ = std::vector<comm_size_t>(num_machines_);
buffer_size_ = 1024 * 1024;
buffer_.resize(buffer_size_);
Log::Info("Local rank: %d, total number of machines: %d", rank_, num_machines_);
}
}
void Network::Init(int num_machines, int rank,
ReduceScatterFunction reduce_scatter_ext_fun, AllgatherFunction allgather_ext_fun) {
if (num_machines > 1) {
rank_ = rank;
num_machines_ = num_machines;
block_start_ = std::vector<comm_size_t>(num_machines_);
block_len_ = std::vector<comm_size_t>(num_machines_);
buffer_size_ = 1024 * 1024;
buffer_.resize(buffer_size_);
reduce_scatter_ext_fun_ = reduce_scatter_ext_fun;
allgather_ext_fun_ = allgather_ext_fun;
Log::Info("Local rank: %d, total number of machines: %d", rank_, num_machines_);
}
}
void Network::Dispose() {
num_machines_ = 1;
rank_ = 0;
linkers_.reset(new Linkers());
reduce_scatter_ext_fun_ = nullptr;
allgather_ext_fun_ = nullptr;
}
void Network::Allreduce(char* input, comm_size_t input_size, int type_size, char* output, const ReduceFunction& reducer) {
if (num_machines_ <= 1) {
Log::Fatal("Please initialize the network interface first");
}
comm_size_t count = input_size / type_size;
// if small package or small count , do it by all gather.(reduce the communication times.)
if (count < num_machines_ || input_size < 4096) {
AllreduceByAllGather(input, input_size, type_size, output, reducer);
return;
}
// assign the blocks to every rank.
comm_size_t step = (count + num_machines_ - 1) / num_machines_;
if (step < 1) {
step = 1;
}
block_start_[0] = 0;
for (int i = 0; i < num_machines_ - 1; ++i) {
block_len_[i] = std::min<comm_size_t>(step * type_size, input_size - block_start_[i]);
block_start_[i + 1] = block_start_[i] + block_len_[i];
}
block_len_[num_machines_ - 1] = input_size - block_start_[num_machines_ - 1];
// do reduce scatter
ReduceScatter(input, input_size, type_size, block_start_.data(), block_len_.data(), output, input_size, reducer);
// do all gather
Allgather(output, block_start_.data(), block_len_.data(), output, input_size);
}
void Network::AllreduceByAllGather(char* input, comm_size_t input_size, int type_size, char* output, const ReduceFunction& reducer) {
if (num_machines_ <= 1) {
Log::Fatal("Please initialize the network interface first");
}
// assign blocks
comm_size_t all_size = input_size * num_machines_;
block_start_[0] = 0;
block_len_[0] = input_size;
for (int i = 1; i < num_machines_; ++i) {
block_start_[i] = block_start_[i - 1] + block_len_[i - 1];
block_len_[i] = input_size;
}
// need use buffer here, since size of "output" is smaller than size after all gather
if (input_size*num_machines_ > buffer_size_) {
buffer_size_ = input_size*num_machines_;
buffer_.resize(buffer_size_);
}
Allgather(input, block_start_.data(), block_len_.data(), buffer_.data(), all_size);
for (int i = 1; i < num_machines_; ++i) {
reducer(buffer_.data() + block_start_[i], buffer_.data() + block_start_[0], type_size, input_size);
}
// copy back
std::memcpy(output, buffer_.data(), input_size);
}
void Network::Allgather(char* input, comm_size_t send_size, char* output) {
if (num_machines_ <= 1) {
Log::Fatal("Please initialize the network interface first");
return;
}
// assign blocks
block_start_[0] = 0;
block_len_[0] = send_size;
for (int i = 1; i < num_machines_; ++i) {
block_start_[i] = block_start_[i - 1] + block_len_[i - 1];
block_len_[i] = send_size;
}
// start all gather
Allgather(input, block_start_.data(), block_len_.data(), output, send_size * num_machines_);
}
void Network::Allgather(char* input, const comm_size_t* block_start, const comm_size_t* block_len, char* output, comm_size_t all_size) {
if (num_machines_ <= 1) {
Log::Fatal("Please initialize the network interface first");
}
if (allgather_ext_fun_ != nullptr) {
return allgather_ext_fun_(input, block_len[rank_], block_start, block_len, num_machines_, output, all_size);
}
const comm_size_t kRingThreshold = 10 * 1024 * 1024; // 10MB
const int kRingNodeThreshold = 64;
if (all_size > kRingThreshold && num_machines_ < kRingNodeThreshold) {
// when num_machines is small and data is large
AllgatherRing(input, block_start, block_len, output, all_size);
} else if (recursive_halving_map_.is_power_of_2) {
AllgatherRecursiveDoubling(input, block_start, block_len, output, all_size);
} else {
AllgatherBruck(input, block_start, block_len, output, all_size);
}
}
void Network::AllgatherBruck(char* input, const comm_size_t* block_start, const comm_size_t* block_len, char* output, comm_size_t all_size) {
comm_size_t write_pos = 0;
// use output as receive buffer
std::memcpy(output, input, block_len[rank_]);
write_pos += block_len[rank_];
int accumulated_block = 1;
for (int i = 0; i < bruck_map_.k; ++i) {
// get current local block size
int cur_block_size = std::min(1 << i, num_machines_ - accumulated_block);
// get out rank
int out_rank = bruck_map_.out_ranks[i];
// get in rank
int in_rank = bruck_map_.in_ranks[i];
// get send information
comm_size_t need_send_len = 0;
// get recv information
comm_size_t need_recv_len = 0;
for (int j = 0; j < cur_block_size; ++j) {
need_send_len += block_len[(rank_ + j) % num_machines_];
need_recv_len += block_len[(rank_ + accumulated_block + j) % num_machines_];
}
// send and recv at same time
linkers_->SendRecv(out_rank, output, need_send_len, in_rank, output + write_pos, need_recv_len);
write_pos += need_recv_len;
accumulated_block += cur_block_size;
}
// rotate in-place
std::reverse<char*>(output, output + all_size);
std::reverse<char*>(output, output + block_start[rank_]);
std::reverse<char*>(output + block_start[rank_], output + all_size);
}
void Network::AllgatherRecursiveDoubling(char* input, const comm_size_t* block_start, const comm_size_t* block_len, char* output, comm_size_t) {
// use output as receive buffer
std::memcpy(output + block_start[rank_], input, block_len[rank_]);
for (int i = 0; i < bruck_map_.k; ++i) {
// get current local block size
int cur_step = 1 << i;
const int vgroup = rank_ / cur_step;
const int vrank = vgroup * cur_step;
int target = rank_ + cur_step;
int target_vrank = (vgroup + 1) * cur_step;
if (vgroup & 1) {
target = rank_ - cur_step;
target_vrank = (vgroup - 1) * cur_step;
}
// get send information
comm_size_t need_send_len = 0;
// get recv information
comm_size_t need_recv_len = 0;
for (int j = 0; j < cur_step; ++j) {
need_send_len += block_len[(vrank + j)];
need_recv_len += block_len[(target_vrank + j)];
}
// send and recv at same time
linkers_->SendRecv(target, output + block_start[vrank], need_send_len,
target, output + block_start[target_vrank], need_recv_len);
}
}
void Network::AllgatherRing(char* input, const comm_size_t* block_start, const comm_size_t* block_len, char* output, comm_size_t) {
// use output as receive buffer
std::memcpy(output + block_start[rank_], input, block_len[rank_]);
int out_rank = (rank_ + 1) % num_machines_;
int in_rank = (rank_ - 1 + num_machines_) % num_machines_;
int out_block = rank_;
int in_block = in_rank;
for (int i = 1; i < num_machines_; ++i) {
// send and recv at same time
linkers_->SendRecv(out_rank, output + block_start[out_block], block_len[out_block],
in_rank, output + block_start[in_block], block_len[in_block]);
out_block = (out_block - 1 + num_machines_) % num_machines_;
in_block = (in_block - 1 + num_machines_) % num_machines_;
}
}
void Network::ReduceScatter(char* input, comm_size_t input_size, int type_size,
const comm_size_t* block_start, const comm_size_t* block_len, char* output,
comm_size_t output_size, const ReduceFunction& reducer) {
if (num_machines_ <= 1) {
Log::Fatal("Please initialize the network interface first");
}
if (reduce_scatter_ext_fun_ != nullptr) {
return reduce_scatter_ext_fun_(input, input_size, type_size, block_start, block_len, num_machines_, output, output_size, reducer);
}
const comm_size_t kRingThreshold = 10 * 1024 * 1024; // 10MB
if (recursive_halving_map_.is_power_of_2 || input_size < kRingThreshold) {
ReduceScatterRecursiveHalving(input, input_size, type_size, block_start, block_len, output, output_size, reducer);
} else {
ReduceScatterRing(input, input_size, type_size, block_start, block_len, output, output_size, reducer);
}
}
void Network::ReduceScatterRecursiveHalving(char* input, comm_size_t input_size, int type_size,
const comm_size_t* block_start, const comm_size_t* block_len, char* output,
comm_size_t, const ReduceFunction& reducer) {
if (!recursive_halving_map_.is_power_of_2) {
if (recursive_halving_map_.type == RecursiveHalvingNodeType::Other) {
// send local data to neighbor first
linkers_->Send(recursive_halving_map_.neighbor, input, input_size);
} else if (recursive_halving_map_.type == RecursiveHalvingNodeType::GroupLeader) {
// receive neighbor data first
int need_recv_cnt = input_size;
linkers_->Recv(recursive_halving_map_.neighbor, output, need_recv_cnt);
// reduce
reducer(output, input, type_size, input_size);
}
}
if (recursive_halving_map_.type != RecursiveHalvingNodeType::Other) {
for (int i = 0; i < recursive_halving_map_.k; ++i) {
// get target
int target = recursive_halving_map_.ranks[i];
comm_size_t send_block_start = recursive_halving_map_.send_block_start[i];
comm_size_t recv_block_start = recursive_halving_map_.recv_block_start[i];
// get send information
comm_size_t send_size = 0;
for (int j = 0; j < recursive_halving_map_.send_block_len[i]; ++j) {
send_size += block_len[send_block_start + j];
}
// get recv information
comm_size_t need_recv_cnt = 0;
for (int j = 0; j < recursive_halving_map_.recv_block_len[i]; ++j) {
need_recv_cnt += block_len[recv_block_start + j];
}
// send and recv at same time
linkers_->SendRecv(target, input + block_start[send_block_start], send_size, target, output, need_recv_cnt);
// reduce
reducer(output, input + block_start[recv_block_start], type_size, need_recv_cnt);
}
}
if (!recursive_halving_map_.is_power_of_2) {
if (recursive_halving_map_.type == RecursiveHalvingNodeType::GroupLeader) {
// send result to neighbor
linkers_->Send(recursive_halving_map_.neighbor,
input + block_start[recursive_halving_map_.neighbor],
block_len[recursive_halving_map_.neighbor]);
} else if (recursive_halving_map_.type == RecursiveHalvingNodeType::Other) {
// receive result from neighbor
int need_recv_cnt = block_len[rank_];
linkers_->Recv(recursive_halving_map_.neighbor, output, need_recv_cnt);
return;
}
}
// copy result
std::memcpy(output, input + block_start[rank_], block_len[rank_]);
}
void Network::ReduceScatterRing(char* input, comm_size_t, int type_size,
const comm_size_t* block_start, const comm_size_t* block_len, char* output,
comm_size_t, const ReduceFunction& reducer) {
const int out_rank = (rank_ + 1) % num_machines_;
const int in_rank = (rank_ - 1 + num_machines_) % num_machines_;
int out_block = in_rank;
int in_block = (in_rank - 1 + num_machines_) % num_machines_;
for (int i = 1; i < num_machines_; ++i) {
linkers_->SendRecv(out_rank, input + block_start[out_block], block_len[out_block],
in_rank, output, block_len[in_block]);
reducer(output, input + block_start[in_block], type_size, block_len[in_block]);
out_block = (out_block - 1 + num_machines_) % num_machines_;
in_block = (in_block - 1 + num_machines_) % num_machines_;
}
std::memcpy(output, input + block_start[rank_], block_len[rank_]);
}
int Network::rank() {
return rank_;
}
int Network::num_machines() {
return num_machines_;
}
} // namespace LightGBM