▶ 計時器函數 MPI_Wtime() 以及頭文件 timer.h 中的宏函數 GET_TIME()，類似 time.h 中函數 clock() 的用法。注意 函數 clock() 記錄的是CPU時間（包含用戶代碼，庫函數，系統調用耗時，不包括空閑等待時間），而 MPI_Wtime() 和 GET_TIME()記錄的是牆上時間（在 CPU 時間的基礎上包括了空閑等待時間）。
● MPI_Wtime() 使用范例
1 { 2 const int globalSize = 8; 3 int globalDataInt[globalSize], i, comSize, comRank, sumInt; 4 double time; 5 6 MPI_Init(&argc, &argv); 7 MPI_Comm_size(MPI_COMM_WORLD, &comSize); 8 MPI_Comm_rank(MPI_COMM_WORLD, &comRank); 9 10 if (comRank == 0) 11 for (i = 0; i < globalSize; globalDataInt[i] = i, i++); 12 13 time = MPI_Wtime(); // 開始計時 14 MPI_Bcast(globalDataInt, globalSize, MPI_DOUBLE, 0, MPI_COMM_WORLD); 15 for (i = sumInt = 0; i < globalSize; sumInt += globalDataInt[i++]); 16 time = MPI_Wtime() - time; // 終止計時 17 18 printf("Size = %d, rank = %d, resultInt = %d, time = %f ms\n", comSize, comRank, sumInt, time * 1000); 19 MPI_Finalize(); 20 return 0; 21 }
● 輸出結果：
D:\Code\MPI\MPIProjectTemp\x64\Debug>mpiexec -n 8 -l MPIProjectTemp.exe [3]Size = 8, rank = 3, resultInt = 28, time = 0.497859 ms [5]Size = 8, rank = 5, resultInt = 28, time = 0.466163 ms [2]Size = 8, rank = 2, resultInt = 28, time = 0.459093 ms [1]Size = 8, rank = 1, resultInt = 28, time = 0.442270 ms [0]Size = 8, rank = 0, resultInt = 28, time = 0.385950 ms [4]Size = 8, rank = 4, resultInt = 28, time = 0.437638 ms [7]Size = 8, rank = 7, resultInt = 28, time = 0.574171 ms [6]Size = 8, rank = 6, resultInt = 28, time = 0.542719 ms
● GET_TIME() 使用范例
1 #include <stdio.h> 2 #include "timer.h" 3 #include <mpi.h> 4 5 int main(int argc, char *argv[]) 6 { 7 const int globalSize = 8; 8 int globalDataInt[globalSize], i, comSize, comRank, sumInt; 9 double timeStart,timeEnd; 10 11 MPI_Init(&argc, &argv); 12 MPI_Comm_size(MPI_COMM_WORLD, &comSize); 13 MPI_Comm_rank(MPI_COMM_WORLD, &comRank); 14 15 if (comRank == 0) 16 for (i = 0; i < globalSize; globalDataInt[i] = i, i++); 17 18 GET_TIME(timeStart); // 開始計時 19 MPI_Bcast(globalDataInt, globalSize, MPI_DOUBLE, 0, MPI_COMM_WORLD); 20 for (i = sumInt = 0; i < globalSize; sumInt += globalDataInt[i++]); 21 GET_TIME(timeEnd); // 終止計時 22 23 printf("Size = %d, rank = %d, resultInt = %d, time = %f ms\n", comSize, comRank, sumInt, (timeEnd - timeStart) * 1000); 24 MPI_Finalize(); 25 return 0; 26 }
● timer.h 的主要內容，我的 time.h 中沒有結構體 struct timeval，無法運行上面的代碼
1 #ifndef _TIMER_H_ 2 #define _TIMER_H_ 3 4 #include <time.h> 5 6 // 注意參數 now 是 double 類型而不是 double* 類型 7 #define GET_TIME(now) {struct timeval t; gettimeofday(&t, NULL); now = t.tv_sec + t.tv_usec/1000000.0; } 8 9 #endif