Parallel Computing in Python using mpi4py

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感覺效果比較好的就是下面的對通信的集合操作的圖解，剛一看比較懵，細一看發現還比較形象。

import numpy as np
from mpi4py import MPI


def rbind(comm, x):
    return np.vstack(comm.allgather(x))


comm = MPI.COMM_WORLD

x = np.arange(4, dtype=np.int) * comm.Get_rank()
a = rbind(comm, x)

print(a)      

import numpy as np
from mpi4py import MPI


def rbind2(comm, x):
    size = comm.Get_size()
    m = np.zeros((size, len(x)), dtype=np.int)
    comm.Allgather([x, MPI.INT], [m, MPI.INT])
    return m


comm = MPI.COMM_WORLD

x = np.arange(4, dtype=np.int) * comm.Get_rank()
a = rbind2(comm, x)

print(a)      

import numpy as np
import math
from mpi4py import MPI


comm = MPI.COMM_WORLD
rank = comm.Get_rank()
size = comm.Get_size()

x = range(20)
m = int(math.ceil(float(len(x)) / size))
x_chunk = x[rank*m:(rank+1)*m]
r_chunk = map(math.sqrt, x_chunk)
r = comm.allreduce(list(r_chunk))

if rank == 0:
    print(len(r), r)