How to share work roughly evenly between processes in MPI despite the array_size not being cleanly divisible by the number of processes?

Question

Hi all, I have an array of length N, and I\'d like to divide it as best as possible between \'size\' processors. N/size has a remainder, e.g. 1000 array elements divided b

Answer 1

Here's a closed-form solution.

Let N = array length and P = number of processors.

From j = 0 to P-1,

Starting point of array on processor j = floor(N * j / P)

Length of array on processor j = floor(N * (j + 1) / P) – floor(N * j / P)