Scattercv displacements greater than int max

Question

I'm trying to distribute a 2D matrix over a number of processors with some overlapping regions. I noticed that the function scatterv of mpi4py doesn't work with 2d arrays, I was forced then to use 1D arrays. The problem here is that the displacements in some processors can be greater than the limit of int. How can I solve this problem please?

import numpy as np
from mpi4py import MPI
from math import ceil

# Dimensions of the matrix
N = 50000
M = 50000

comm = MPI.COMM_WORLD
size = comm.Get_size()
rank = comm.Get_rank()
n = ceil(N/size)
offset = N-(size-1)*n  # Offset
start = np.zeros(size, dtype=np.float64)  # Start rows of the chunks
end = np.zeros(size, dtype=np.float64)  # End rows of the chunks
sz_loc = np.zeros(size, dtype=np.float64)  # Size of he local chunk
for i in range(size):

    pp = n 
    if i == size - 1:
        pp = offset
    start[i] = max(0, i * n - mf)
    end[i] = min(N, i * n + pp + mf)
    sz_loc[i] = (end[i]-start[i])*M

if rank == 0:

    Im = np.array(np.round(10*np.random.rand(N, M)),
                  dtype=np.float32).ravel()  

else: 
    Im = None 

Im_loc = np.zeros((int(sz_loc[rank]),), dtype=np.float32)
comm.Barrier()

comm.Scatterv([Im, sz_loc, start*M, MPI.FLOAT], Im_loc, root=0)

Here is the error I get, using for the example 10 processors

 comm.Scatterv([Im, sz_loc, start*M, MPI.FLOAT], Im_loc, root=0)
  File "mpi4py/MPI/Comm.pyx", line 626, in mpi4py.MPI.Comm.Scatterv
  File "mpi4py/MPI/msgbuffer.pxi", line 538, in mpi4py.MPI._p_msg_cco.for_scatter
  File "mpi4py/MPI/msgbuffer.pxi", line 440, in mpi4py.MPI._p_msg_cco.for_cco_send
  File "mpi4py/MPI/msgbuffer.pxi", line 313, in mpi4py.MPI.message_vector
  File "mpi4py/MPI/asarray.pxi", line 22, in mpi4py.MPI.chkarray
  File "mpi4py/MPI/asarray.pxi", line 15, in mpi4py.MPI.getarray
OverflowError: value too large to convert to int

Answer 1

Finally I definded a new data type using Create_contiguous() function.