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45 lines
1014 B
45 lines
1014 B
#!/usr/bin/env python
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"""
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Parallel PI computation using Collective Communication Operations (CCO)
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within Python objects exposing memory buffers (requires NumPy).
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usage::
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$ mpiexec -n <nprocs> python cpi-buf.py
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"""
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from mpi4py import MPI
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from math import pi as PI
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from numpy import array
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def comp_pi(n, myrank=0, nprocs=1):
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h = 1.0 / n
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s = 0.0
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for i in range(myrank + 1, n + 1, nprocs):
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x = h * (i - 0.5)
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s += 4.0 / (1.0 + x**2)
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return s * h
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def prn_pi(pi, PI):
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message = "pi is approximately %.16f, error is %.16f"
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print (message % (pi, abs(pi - PI)))
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comm = MPI.COMM_WORLD
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nprocs = comm.Get_size()
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myrank = comm.Get_rank()
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n = array(0, dtype=int)
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pi = array(0, dtype=float)
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mypi = array(0, dtype=float)
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if myrank == 0:
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_n = 10000000
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n.fill(_n)
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comm.Bcast([n, MPI.INT], root=0)
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_mypi = comp_pi(n, myrank, nprocs)
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mypi.fill(_mypi)
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comm.Reduce([mypi, MPI.DOUBLE], [pi, MPI.DOUBLE],
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op=MPI.SUM, root=0)
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if myrank == 0:
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prn_pi(pi, PI)
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