Added a non-trivial example of MPI.

Author: Jonathan Rocher

ParallelComputing/compute_pi_mpi.py

@@ -0,0 +1,33 @@
+# -*- coding: utf-8 -*-
+from mpi4py import MPI
+import math
+
+def compute_pi(n, start=0, step=1):
+    """ Pure python integration of 4/(1+x**2) which gives pi
+    """
+    h = 1.0 / n
+    s = 0.0
+    for i in range(start, n, step):
+        x = h * (i + 0.5)
+        s += 4.0 / (1.0 + x**2)
+    return s * h
+    
+comm = MPI.COMM_WORLD
+nprocs = comm.Get_size()
+myrank = comm.Get_rank()
+
+if myrank == 0:
+    n = 10
+else:
+    n = None
+    
+n = comm.bcast(n, root=0)
+
+mypi = compute_pi(n, myrank, nprocs)
+
+pi = comm.reduce(mypi, op=MPI.SUM, root=0)
+
+if myrank == 0:
+    error = abs(pi - math.pi)
+    print ("pi is approximately %.16f, "
+           "error is %.16f" % (pi, error))

pickle/pickle.py

@@ -24,4 +24,4 @@ def recover_from_file(filename):
     filename = "myinfo.pkl"
     save2file(info,filename)
     new_obj = recover_from_file(filename)
-    print "object recovered is", new_obj
+    print "Object recovered is identical?", new_obj.__dict__ == info.__dict__