Changes between Version 6 and Version 7 of mpich/test/cpi

Timestamp:

Apr 14, 2008, 11:36:33 AM (17 years ago)

Author:

wade

Comment:

--

mpich/test/cpi

@@ -1 +1 @@
 = CPI 的 loop 只會跑一次 =
+{{{
+#include "mpi.h"
+#include <stdio.h>
+#include <math.h>
 
+double f( double );
+double f( double a )
+{
+    return (4.0 / (1.0 + a*a));
+}
 
+int main( int argc, char *argv[])
+{
+    int done = 0, n, myid, numprocs, i, count=0;
+    double PI25DT = 3.141592653589793238462643;
+    double mypi, pi, h, sum, x;
+    double startwtime = 0.0, endwtime;
+    int  namelen;
+    char processor_name[MPI_MAX_PROCESSOR_NAME];
+
+    MPI_Init(&argc,&argv);
+    MPI_Comm_size(MPI_COMM_WORLD,&numprocs);
+    MPI_Comm_rank(MPI_COMM_WORLD,&myid);
+    MPI_Get_processor_name(processor_name,&namelen);
+
+    fprintf(stderr,"Process %d on %s\n",
+            myid, processor_name);
+
+    n = 0;
+    while (!done)
+    {
+
+/* 註 1: 我在這邊開始計算 loop 執行的次數 */
+    count++;
+        if (myid == 0)
+        {
+/*
+            printf("Enter the number of intervals: (0 quits) ");
+            scanf("%d",&n);
+*/
+            if (n==0) n=100; else n=0;
+
+            startwtime = MPI_Wtime();
+        }
+        MPI_Bcast(&n, 1, MPI_INT, 0, MPI_COMM_WORLD);
+        if (n == 0)
+            done = 1;
+        else
+        {
+            h   = 1.0 / (double) n;
+            sum = 0.0;
+            for (i = myid + 1; i <= n; i += numprocs)
+            {
+                x = h * ((double)i - 0.5);
+                sum += f(x);
+            }
+            mypi = h * sum;
+
+            MPI_Reduce(&mypi, &pi, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD);
+
+/* 註 2: 在這邊我把每個 node 所執行的 loop 次數印出 */
+            if (myid == 0)
+            {
+                printf("pi is approximately %.16f, Error is %.16f\n",
+                       pi, fabs(pi - PI25DT));
+                endwtime = MPI_Wtime();
+                printf("wall clock time = %f\n",
+                       endwtime-startwtime);           
+                printf("Node 0 loop runs  %d  times\n", count);
+            } else
+            {
+                printf("Node not 0 loop runs  %d  times\n", count);
+            }
+
+        }
+    }
+    MPI_Finalize();
+    return 0;
+}
+}}}
+結果