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私は1000までのすべての数値の合計を計算するプログラムを書いています。たとえば、1 + 2 + 3 + 4 + 5 .... + 100です。まず、10のプロセッサに合計ジョブを割り当てます。プロセッサ0は1〜100、プロセッサ1は101〜200などを取得します。合計は配列に格納されます。MPI（Summation）
すべての集計が並列処理された後、プロセッサはプロセッサ0に値を送信します（プロセッサ0は非ブロック送信/ recvを使用して値を受け取ります）。プロセッサ0はすべての値を合計し、結果を表示します。
#include <mpi.h>
#include <iostream>
using namespace std;
int summation(int, int);
int main(int argc, char ** argv)
{
int * array;
int total_proc;
int curr_proc;
int limit = 0;
int partial_sum = 0;
int upperlimit = 0, lowerlimit = 0;
MPI_Init(&argc, &argv);
MPI_Comm_size(MPI_COMM_WORLD, &total_proc);
MPI_Comm_rank(MPI_COMM_WORLD, &curr_proc);
MPI_Request send_request, recv_request;
/* checking if 1000 is divisible by number of procs, else quit */
if(1000 % total_proc != 0)
{
MPI_Finalize();
if(curr_proc == 0)
cout << "**** 1000 is not divisible by " << total_proc << " ...quitting..."<< endl;
return 0;
}
/* number of partial summations */
limit = 1000/total_proc;
array = new int [total_proc];
/* assigning jobs to processors */
for(int i = 0; i < total_proc; i++)
{
if(curr_proc == i)
{
upperlimit = upperlimit + limit;
lowerlimit = (upperlimit - limit) + 1;
partial_sum = summation(upperlimit, lowerlimit);
array[i] = partial_sum;
}
else
{
upperlimit = upperlimit + limit;
lowerlimit = (upperlimit - limit) + 1;
}
}
cout << "** Partial Sum From Process " << curr_proc << " is " << array[curr_proc] << endl;
/* send and receive - non blocking */
for(int i = 1; i < total_proc; i++)
{
if(curr_proc == i) /* (i = current processor) */
{
MPI_Isend(&array[i], 1, MPI_INT, 0, i, MPI_COMM_WORLD, &send_request);
cout << "-> Process " << i << " sent " << array[i] << " to Process 0" << endl;
MPI_Irecv(&array[i], 1, MPI_INT, i, i, MPI_COMM_WORLD, &recv_request);
//cout << "<- Process 0 received " << array[i] << " from Process " << i << endl;
}
}
MPI_Finalize();
if(curr_proc == 0)
{
for(int i = 1; i < total_proc; i++)
array[0] = array[0] + array[i];
cout << "Sum is " << array[0] << endl;
}
return 0;
}
int summation(int u, int l)
{
int result = 0;
for(int i = l; i <= u; i++)
result = result + i;
return result;
}
出力：
** Partial Sum From Process 0 is 5050
** Partial Sum From Process 3 is 35050
-> Process 3 sent 35050 to Process 0
<- Process 0 received 35050 from Process 3
** Partial Sum From Process 4 is 45050
-> Process 4 sent 45050 to Process 0
<- Process 0 received 45050 from Process 4
** Partial Sum From Process 5 is 55050
-> Process 5 sent 55050 to Process 0
<- Process 0 received 55050 from Process 5
** Partial Sum From Process 6 is 65050
** Partial Sum From Process 8 is 85050
-> Process 8 sent 85050 to Process 0
<- Process 0 received 85050 from Process 8
-> Process 6 sent 65050 to Process 0
** Partial Sum From Process 1 is 15050
** Partial Sum From Process 2 is 25050
-> Process 2 sent 25050 to Process 0
<- Process 0 received 25050 from Process 2
<- Process 0 received 65050 from Process 6
** Partial Sum From Process 7 is 75050
-> Process 1 sent 15050 to Process 0
<- Process 0 received 15050 from Process 1
-> Process 7 sent 75050 to Process 0
<- Process 0 received 75050 from Process 7
** Partial Sum From Process 9 is 95050
-> Process 9 sent 95050 to Process 0
<- Process 0 received 95050 from Process 9
Sum is -1544080023
配列の内容を出力：私はこれを引き起こしているものを知りたい
5050
536870912
-1579286148
-268433415
501219332
32666
501222192
32666
1
0
ここ
はコードです。MPI_Finalizeが呼び出される前に配列を印刷すると問題なく動作します。