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April 29, 2019 15:58
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A modified version of the Pi-calculation script from the mpi4py repository.
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| from mpi4py import MPI | |
| from math import pi as PI | |
| from numpy import array | |
| def comp_pi(n, myrank=0, nprocs=1): | |
| h = 1.0 / n | |
| s = 0.0 | |
| for i in range(myrank + 1, n + 1, nprocs): | |
| x = h * (i - 0.5) | |
| s += 4.0 / (1.0 + x**2) | |
| return s * h | |
| def prn_pi(pi, PI): | |
| message = "pi is approximately %.16f, error is %.16f" | |
| print (message % (pi, abs(pi - PI))) | |
| comm = MPI.COMM_WORLD | |
| nprocs = comm.Get_size() | |
| myrank = comm.Get_rank() | |
| n = array(0, dtype=int) | |
| pi = array(0, dtype=float) | |
| mypi = array(0, dtype=float) | |
| if myrank == 0: | |
| _n = 20 # Enter the number of intervals | |
| n.fill(_n) | |
| comm.Bcast([n, MPI.INT], root=0) | |
| _mypi = comp_pi(n, myrank, nprocs) | |
| mypi.fill(_mypi) | |
| comm.Reduce([mypi, MPI.DOUBLE], [pi, MPI.DOUBLE], | |
| op=MPI.SUM, root=0) | |
| if myrank == 0: | |
| prn_pi(pi, PI) |
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