Codes pour l'approximation de pi

calculquebec · May 14, 2024 · 08f6f95 · 08f6f95
1 parent 92b31b2
commit 08f6f95
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Showing 5 changed files with 123 additions and 25 deletions.
diff --git a/exercices/pi_collect.c b/exercices/pi_collect.c
@@ -4,12 +4,12 @@
 
 int main(int argc, char *argv[])
 {
-    int rank, size, n, i;
-    double sum, pi;
+    int rank, size, n, debut, fin, k;
+    double somme, pi;
 
-    MPI_Init( &argc, &argv );
-    MPI_Comm_size( MPI_COMM_WORLD, &size );
-    MPI_Comm_rank( MPI_COMM_WORLD, &rank );
+    MPI_Init(&argc, &argv);
+    MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+    MPI_Comm_size(MPI_COMM_WORLD, &size);
 
     do {
         if (rank == 0) {
@@ -22,16 +22,19 @@ int main(int argc, char *argv[])
         MPI_Bcast( ... );
         if (n == 0) break;
 
-        sum = 0.0;
-        for (i = n - 1 - rank; i >= 0; i -= size) {
-            sum += (4.0 - 8.0 * (i % 2)) / (2.0 * i + 1);
+        debut = ... (long)n ...
+        fin = ... (long)n ...
+
+        somme = 0.0;
+        for (k = fin - 1; k >= debut; --k) {
+            somme += (4.0 - 8.0 * (k % 2)) / (2.0 * k + 1);
         }
 
         MPI_Reduce( ... );
 
         if (rank == 0) {
-            printf("PI is approximately %.16f, Error is %.16f\n",
-                pi, fabs(pi - M_PI));
+            printf("PI is approximately %.16f, difference is %.16f\n",
+                   pi, fabs(pi - M_PI));
         }
     } while (1);
 

diff --git a/exercices/pi_collect.in b/exercices/pi_collect.in
@@ -1,4 +1,5 @@
-1000
+100
+10000
 1000000
-1000000000
+100000000
 0
diff --git a/exercices/pi_collect.py b/exercices/pi_collect.py
@@ -0,0 +1,44 @@
+#!/usr/bin/env python
+
+from mpi4py import MPI  # MPI.Init() implicite
+import math
+import sys
+
+
+def main():
+    """
+    Programme principal
+    """
+
+    comm = MPI.COMM_WORLD
+    rank = comm.Get_rank()
+    size = comm.Get_size()
+    n = None
+
+    while True:
+        if rank == 0:
+            n = int(input('Enter the number of intervals (0 quits): '))
+            print(f'-> {n} iterations' if n > 0 else 'done')
+
+        bcast( ... )
+        if n == 0:
+            break
+
+        debut = ... n ...
+        fin = ... n ...
+
+        somme = 0.0;
+        for k in range(fin - 1, debut - 1, -1):
+            somme += (4.0 - 8.0 * (k % 2)) / (2.0 * k + 1)
+
+        reduce( ... )
+
+        if rank == 0:
+            print(f'PI is approximately {pi:.16f},',
+                  f'difference is {abs(pi - math.pi):.16f}')
+
+    MPI.Finalize()
+
+
+if __name__ == '__main__':
+    main()
diff --git a/exercices/solutions/pi_collect.c b/exercices/solutions/pi_collect.c
@@ -4,12 +4,12 @@
 
 int main(int argc, char *argv[])
 {
-    int rank, size, n, i;
-    double sum, pi, t1, t2;
+    int rank, size, n, debut, fin, k;
+    double somme, pi, t1, t2;
 
-    MPI_Init( &argc, &argv );
-    MPI_Comm_size( MPI_COMM_WORLD, &size );
-    MPI_Comm_rank( MPI_COMM_WORLD, &rank );
+    MPI_Init(&argc, &argv);
+    MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+    MPI_Comm_size(MPI_COMM_WORLD, &size);
 
     do {
         if (rank == 0) {
@@ -20,21 +20,24 @@ int main(int argc, char *argv[])
             t1 = MPI_Wtime();
         }
 
-        MPI_Bcast( &n, 1, MPI_INT, 0, MPI_COMM_WORLD );
+        MPI_Bcast(&n, 1, MPI_INT, 0, MPI_COMM_WORLD);
         if (n == 0) break;
 
-        sum = 0.0;
-        for (i = n - 1 - rank; i >= 0; i -= size) {
-            sum += (4.0 - 8.0 * (i % 2)) / (2.0 * i + 1);
+        debut = rank * (long)n / size;
+        fin = (rank + 1) * (long)n / size;
+
+        somme = 0.0;
+        for (k = fin - 1; k >= debut; --k) {
+            somme += (4.0 - 8.0 * (k % 2)) / (2.0 * k + 1);
         }
 
-        MPI_Reduce( &sum, &pi, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD );
+        MPI_Reduce(&somme, &pi, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD);
 
         if (rank == 0) {
             t2 = MPI_Wtime();
-            printf("PI is approximately %.16f, Error is %.16f\n",
-                pi, fabs(pi - M_PI));
-            printf("Time = %.16f sec\n", t2 - t1);
+            printf("PI is approximately %.16f, difference is %.16f\n",
+                   pi, fabs(pi - M_PI));
+            printf("Time = %.6f sec\n", t2 - t1);
         }
     } while (1);
 

diff --git a/exercices/solutions/pi_collect.py b/exercices/solutions/pi_collect.py
@@ -0,0 +1,47 @@
+#!/usr/bin/env python
+
+from mpi4py import MPI  # MPI.Init() implicite
+import math
+import sys
+
+
+def main():
+    """
+    Programme principal
+    """
+
+    comm = MPI.COMM_WORLD
+    rank = comm.Get_rank()
+    size = comm.Get_size()
+    n = None
+
+    while True:
+        if rank == 0:
+            n = int(input('Enter the number of intervals (0 quits): '))
+            print(f'-> {n} iterations' if n > 0 else 'done')
+            t1 = MPI.Wtime()
+
+        n = comm.bcast(n, 0)
+        if n == 0:
+            break
+
+        debut = rank * n // size
+        fin = (rank + 1) * n // size
+
+        somme = 0.0;
+        for k in range(fin - 1, debut - 1, -1):
+            somme += (4.0 - 8.0 * (k % 2)) / (2.0 * k + 1)
+
+        pi = comm.reduce(somme, MPI.SUM, 0)
+
+        if rank == 0:
+            t2 = MPI.Wtime()
+            print(f'PI is approximately {pi:.16f},',
+                  f'difference is {abs(pi - math.pi):.16f}')
+            print(f'Time = {t2 - t1:.6f} sec')
+
+    MPI.Finalize()
+
+
+if __name__ == '__main__':
+    main()