---
title: kpccl_shm_allreduce_init
description: "进程间allreduce初始化。"
url: https://www.hikunpeng.com/document/detail/zh/hpchistory/hpckit/develop2400/KunoengHPCKit_developer_063.html
sourcePath: /source/zh/hpchistory/hpckit/develop2400/KunoengHPCKit_developer_063.html
indexId: 44111ec2a69b858435bf05f2f8fb7765ec687bdc3fb8d01f960b7717cbe6ac7373
---
# kpccl_shm_allreduce_init

进程间allreduce初始化。

#### 接口定义

int kpccl_shm_allreduce_init(const void *sendbuf, void *recvbuf, int count, kpccl_shm_datatype_t datatype, kpccl_shm_reduce_op_t op, kpccl_shm_comm_h comm, kpccl_shm_request_t *request);


#### 环境变量

allreduce 可以使用环境变量指定算法。

环境变量名称为KPCCL_SHM_ALLREDUCE_ALGORITHM，可选值：

- 0：代表auto_tunning（默认）
- 1：代表rb（rh_rd）算法
- 2：代表linear 算法


#### 参数


**表1 参数定义**

| 参数名 | 类型 | 描述 | 输入/输出 |
| --- | --- | --- | --- |
| sendbuf | const void \* | 需要的send buffer | 输入 |
| recvbuf | void \* | 需要的recv buffer | 输入 |
| count | int | 需要的send count | 输入 |
| datatype | kpccl\_shm\_datatype\_t | 需要的数据类型，可设置为KPCCL\_SHM\_DATATYPE\_CHAR, KPCCL\_SHM\_DATATYPE\_INT, KPCCL\_SHM\_DATATYPE\_LONG, KPCCL\_SHM\_DATATYPE\_FLOAT, KPCCL\_SHM\_DATATYPE\_DOUBLE | 输入 |
| op | kpccl\_shm\_reduce\_op\_t | 需要的归约操作，可设置为KPCCL\_SHM\_REDUCE\_OP\_MAX, KPCCL\_SHM\_REDUCE\_OP\_MIN, KPCCL\_SHM\_REDUCE\_OP\_SUM | 输入 |
| comm | kpccl\_shm\_comm\_h | 需要的kpccl comm | 输入 |
| request | kpccl\_shm\_request\_t \* | 生成的持久化request | 输出 |


#### 返回值

- 成功：返回KPCCL_OK
- 失败：返回KPCCL_ERROR


#### 示例

```
#include <stdio.h>
#include <mpi.h>
#include <math.h>
#include "kpccl.h"
int oob_allgather_callback(const void *sendbuf, void *recvbuf, int size, void *group，kpccl_shm_datatype_t datatype)
{
switch (datatype) {
case KPCCL_SHM_DATATYPE_CHAR:
return MPI_Allgather(sendbuf, size, MPI_CHAR, recvbuf, size, MPI_CHAR, (MPI_Comm)group);
case KPCCL_SHM_DATATYPE_INT:
return MPI_Allgather(sendbuf, size, MPI_INT, recvbuf, size, MPI_INT, (MPI_Comm)group);
case KPCCL_SHM_DATATYPE_LONG:
return MPI_Allgather(sendbuf, size, MPI_LONG, recvbuf, size, MPI_LONG, (MPI_Comm)group);
case KPCCL_SHM_DATATYPE_FLOAT:
return MPI_Allgather(sendbuf, size, MPI_FLOAT, recvbuf, size, MPI_FLOAT, (MPI_Comm)group);
case KPCCL_SHM_DATATYPE_DOUBLE:
return MPI_Allgather(sendbuf, size, MPI_DOUBLE, recvbuf, size, MPI_DOUBLE, (MPI_Comm)group);
default:
kpccl_error("not support datatype");
return KPCCL_ERROR;
}
}
int
oob_barrier_callback(
void
*
group)
{
return MPI_Barrier((MPI_Comm)group);
}
int main()
{
int check = 1;
int myid, numprocs;
MPI_Comm comm = MPI_COMM_WORLD;
MPI_Comm_size(comm, &numprocs);
MPI_Comm_rank(comm, &myid);
kpccl_shm_oob_cb_t oob_cbs;
kpccl_shm_oob_cb_h oob_cbs_h = &oob_cbs;
oob_cbs_h->oob_allgather = oob_allgather_callback;
oob_cbs_h->oob_barrier = oob_barrier_callback;
kpccl_shm_comm_h kpccl_comm;
kpccl_shm_comm_create(numprocs, myid, myid, oob_cbs_h, (void *)comm, &kpccl_comm);
kpccl_shm_win_h win_send;
kpccl_shm_win_h win_recv;
kpccl_shm_win_h ompi_win_recv;
void *sendbuf;
void *recvbuf;
void *ompibuf;
int count = 16000;
size_t buf_size = sizeof(float) * count;
kpccl_shm_win_alloc(buf_size, kpccl_comm, &sendbuf, &win_send);
kpccl_shm_win_alloc(buf_size, kpccl_comm, &recvbuf, &win_recv);
kpccl_shm_win_alloc(buf_size, kpccl_comm, &ompibuf, &ompi_win_recv);
auto t_sendbuf = static_cast<float *>(sendbuf);
auto t_recvbuf = static_cast<float *>(recvbuf);
auto t_ompibuf = static_cast<float *>(ompibuf);
for (int i = 0; i < count; i++) {
t_sendbuf[i] = myid + i;
}
kpccl_shm_datatype datatype = KPCCL_SHM_DATATYPE_FLOAT;
MPI_Datatype mpi_datatype = MPI_FLOAT;
kpccl_shm_request_h request;
MPI_Barrier(comm);
kpccl_shm_allreduce_init
(sendbuf, recvbuf, count, datatype, KPCCL_SHM_REDUCE_OP_SUM, kpccl_comm, &request);
kpccl_shm_request_start(request);
kpccl_shm_request_wait(request);
kpccl_shm_request_free(request);
MPI_Barrier(comm);
MPI_Allreduce(sendbuf, ompibuf, count, mpi_datatype, MPI_SUM, comm);
for (int i = 0; i < count; i++) {
if (abs(t_recvbuf[i] - t_ompibuf[i]) > 1e-6) {
check = 0;
}
}
int result;
MPI_Reduce(&check, &result, 1, MPI_INT, MPI_SUM, 0, comm);
if (result == 0) {
printf("check success\n");
} else {
printf("check failed\n");
}
}
kpccl_shm_win_free(win_send);
kpccl_shm_win_free(win_recv);
kpccl_shm_win_free(ompi_win_recv);
kpccl_shm_comm_destroy(kpccl_comm);
}
```

运行结果如下。

```
check success
```

上述示例演示了kpccl allreduce的流程。kpccl_shm_allreduce_init函数初始化allreduce的request。