MPI 计时器函数 MPI_Wtime()

▶ 计时器函数 MPI_Wtime() 以及头文件 timer.h 中的宏函数 GET_TIME()，类似 time.h 中函数 clock() 的用法。注意 函数 clock() 记录的是CPU时间（包含用户代码，库函数，系统调用耗时，不包括空闲等待时间），而 MPI_Wtime() 和 GET_TIME()记录的是墙上时间（在 CPU 时间的基础上包括了空闲等待时间）。

● MPI_Wtime() 使用范例

 {
     const int globalSize = ;
     int globalDataInt[globalSize], i, comSize, comRank, sumInt;
     double time;

     MPI_Init(&argc, &argv);
     MPI_Comm_size(MPI_COMM_WORLD, &comSize);
     MPI_Comm_rank(MPI_COMM_WORLD, &comRank);

     if (comRank == )
         for (i = ; i < globalSize; globalDataInt[i] = i, i++);

     time = MPI_Wtime();         // 开始计时
     MPI_Bcast(globalDataInt, globalSize, MPI_DOUBLE, , MPI_COMM_WORLD);
     for (i = sumInt = ; i < globalSize; sumInt += globalDataInt[i++]);
     time = MPI_Wtime() - time;  // 终止计时

     printf("Size = %d, rank = %d, resultInt = %d, time = %f ms\n", comSize, comRank, sumInt, time * );
     MPI_Finalize();
     return ;
 }

● 输出结果：

D:\Code\MPI\MPIProjectTemp\x64\Debug>mpiexec -n  -l MPIProjectTemp.exe
[]Size = , rank = , resultInt = , time = 0.497859 ms
[]Size = , rank = , resultInt = , time = 0.466163 ms
[]Size = , rank = , resultInt = , time = 0.459093 ms
[]Size = , rank = , resultInt = , time = 0.442270 ms
[]Size = , rank = , resultInt = , time = 0.385950 ms
[]Size = , rank = , resultInt = , time = 0.437638 ms
[]Size = , rank = , resultInt = , time = 0.574171 ms
[]Size = , rank = , resultInt = , time = 0.542719 ms

● GET_TIME() 使用范例

 #include <stdio.h>
 #include "timer.h"
 #include <mpi.h>

 int main(int argc, char *argv[])
 {
     const int globalSize = ;
     int globalDataInt[globalSize], i, comSize, comRank, sumInt;
     double timeStart,timeEnd;

     MPI_Init(&argc, &argv);
     MPI_Comm_size(MPI_COMM_WORLD, &comSize);
     MPI_Comm_rank(MPI_COMM_WORLD, &comRank);

     if (comRank == )
         for (i = ; i < globalSize; globalDataInt[i] = i, i++);

     GET_TIME(timeStart);         // 开始计时
     MPI_Bcast(globalDataInt, globalSize, MPI_DOUBLE, , MPI_COMM_WORLD);
     for (i = sumInt = ; i < globalSize; sumInt += globalDataInt[i++]);
     GET_TIME(timeEnd);          // 终止计时

     printf("Size = %d, rank = %d, resultInt = %d, time = %f ms\n", comSize, comRank, sumInt, (timeEnd - timeStart) * );
     MPI_Finalize();
     return ;
 }

● timer.h 的主要内容，我的 time.h 中没有结构体 struct timeval，无法运行上面的代码

 #ifndef _TIMER_H_
 #define _TIMER_H_

 #include <time.h>

 // 注意参数 now 是 double 类型而不是 double* 类型
 #define GET_TIME(now) {struct timeval t; gettimeofday(&t, NULL); now = t.tv_sec + t.tv_usec/1000000.0; }

 #endif