測量OpenMPI中進程之間的數據傳輸

Question

我正在使用ubuntu和OpenMPI 1.4進行集羣工作。我的代碼運行良好，但我想測量在根進程和從屬節點之間發送數據的時間。

我認爲我的代碼沒有給我正確的信息。

void invertColor_Parallel(struct image *im, int size, int rank,clock_t *sendTime) 
{ 
    clock_t begin; 

    int i,j,lum,aux,r; 

    int total_pixels = (*im).ih.width * (*im).ih.height; 
    int qty = total_pixels/(size-1); 
    int rest = total_pixels % (size-1); 
    MPI_Status status; 

    //printf("\n%d\n", rank); 

    if(rank == 0) 
    { 
     begin = MPI_Wtime(); 
     for(i=1; i<size; i++){ 
     j = i*qty - qty; 
     aux = j; 

     if(rest != 0 && i==size-1) {qty=qty+rest;} //para distrubuir toda la carga 
     //printf("\nj: %d qty: %d rest: %d\n", j, qty, rest); 


     MPI_Send(&aux, 1, MPI_INT, i, MASTER_TO_SLAVE_TAG+1, MPI_COMM_WORLD); 
     MPI_Send(&qty, 1, MPI_INT, i, MASTER_TO_SLAVE_TAG+2, MPI_COMM_WORLD); 
     MPI_Send(&(*im).array[j], qty*3, MPI_BYTE, i, MASTER_TO_SLAVE_TAG, MPI_COMM_WORLD); 


     //printf("\nSending to node=%d, sender node=%d\n", i, rank); 
     } 
     *sendTime+=MPI_Wtime()-begin; 

    } 
    else 
    { 
     MPI_Recv(&aux, 1, MPI_INT, MPI_ANY_SOURCE, MASTER_TO_SLAVE_TAG+1, MPI_COMM_WORLD,&status); 
     MPI_Recv(&qty, 1, MPI_INT, MPI_ANY_SOURCE, MASTER_TO_SLAVE_TAG+2, MPI_COMM_WORLD,&status); 

     pixel *arreglo = (pixel *)calloc(qty, sizeof(pixel)); 
     MPI_Recv(&arreglo[0], qty*3, MPI_BYTE, MPI_ANY_SOURCE, MASTER_TO_SLAVE_TAG, MPI_COMM_WORLD,&status); 
     //printf("Receiving node=%d, message=%d\n", rank, aux); 

     for(i=0;i<qty;i++) 
     { 
      arreglo[i].R = 255-arreglo[i].R; 
      arreglo[i].G = 255-arreglo[i].G; 
      arreglo[i].B = 255-arreglo[i].B; 
     } 

     MPI_Send(&aux, 1, MPI_INT, 0, SLAVE_TO_MASTER_TAG+1, MPI_COMM_WORLD); 
     MPI_Send(&qty, 1, MPI_INT, 0, SLAVE_TO_MASTER_TAG+2, MPI_COMM_WORLD); 
     MPI_Send(&arreglo[0], qty*3, MPI_BYTE, 0, SLAVE_TO_MASTER_TAG, MPI_COMM_WORLD); 

     free(arreglo); 
    } 


    if (rank==0){ 
    //printf("\nrank: %d\n", rank); 
     begin=MPI_Wtime(); 
     for (i=1; i<size; i++) // untill all slaves have handed back the processed data 
     { 
      MPI_Recv(&aux, 1, MPI_INT, MPI_ANY_SOURCE, SLAVE_TO_MASTER_TAG+1, MPI_COMM_WORLD, &status); 
      MPI_Recv(&qty, 1, MPI_INT, status.MPI_SOURCE, SLAVE_TO_MASTER_TAG+2, MPI_COMM_WORLD, &status); 
      MPI_Recv(&(*im).array[aux], qty*3, MPI_BYTE, status.MPI_SOURCE, SLAVE_TO_MASTER_TAG, MPI_COMM_WORLD, &status); 
     } 
     *sendTime+=MPI_Wtime()-begin; 
    } 
} 

void runningTime(clock_t begin, clock_t end,clock_t sendTime) 
{ 
    double time_spent; 

    time_spent = (double)(end - begin)/CLOCKS_PER_SEC; 
    printf("Tiempo con Latencia: %f\n", time_spent); 
    time_spent-=(double) sendTime/CLOCKS_PER_SEC; 
    printf("Tiempo de envio: %f\n", time_spent); 
    printf("Tiempo de latencia: %f\n\n", (double) sendTime/CLOCKS_PER_SEC); 
} 

int main(int argc, char *argv[]) 
{ 
    //////////time counter 
    clock_t begin,sendTime=(clock_t) 0.0; 


    int rank, size; 

    MPI_Init(&argc, &argv); 
    MPI_Comm_size(MPI_COMM_WORLD, &size); 
    MPI_Comm_rank(MPI_COMM_WORLD, &rank); 
    MPI_Status status; 

    int op = (int)atof(argv[1]); 
    struct image image2; 

    if (rank==0) 
    { 
     loadImage(&image2, argv[2]); 
    } 

    //Broadcast the user's choice to all other ranks 
    MPI_Bcast(&op, 1, MPI_INT, 0, MPI_COMM_WORLD); 


    switch(op) 
    { 
     case 1: 
       if (rank==0) {begin = clock();} 
       MPI_Barrier(MPI_COMM_WORLD); 
       invertColor_Parallel(&image2, size, rank,&sendTime); 
       MPI_Barrier(MPI_COMM_WORLD); 
       if (rank==0) {runningTime(begin, clock(),sendTime); printf("Se invirtieron los colores de la imagen\n\n");} 
       break; 
    } 

    MPI_Barrier(MPI_COMM_WORLD); 

    if (rank==0) 
    { 
     saveImage(&image2, argv[3]); 
     free(image2.array); 
    } 

    MPI_Finalize(); 

    return 0; 
} 

我要測量的過程和功能的ivertColor_Parallel整個時間之間的數據傳輸時間。我究竟做錯了什麼？。

非常感謝。

Answer 1

MPI_Wtime()返回一個雙精度浮點數，該數值給出從過去的某個點開始經過的秒的數量。 clock_t是一個整數類型。首先，當您將結果從MPI_Wtime()轉換爲clock_t時，您將失去小數部分（亞秒）精度。其次，在將結果clock_t的值除以CLOCKS_PER_SEC（在Linux等POSIX系統上等於1000000）之後，結果始終爲0，除非在兩個調用MPI_Wtime()之間已超過11天和14小時。

MPI_Wtime()用法是簡單的：

double begin = MPI_Wtime(); 
... 
double end = MPI_Wtime(); 
printf("Time elapsed: %f seconds\n", end - begin);