Allocation of distributed arrays to workers

General Usage
1

By default when creating a distributed array each worker is assigned consecutive fields.

So for a 10 element array, worker 1 would control 1:5 and worker 2 6:10.

¿Is there a way of defining the DArrays in a way that worker 1 takes care of the odd elements and worker 2 of the even elements?

Thank you!

2

You can do this with SharedArrays:

julia> using Distributed
julia> addprocs(2)
julia> @everywhere using SharedArrays
julia> S = SharedArray{Int,1}(10, init = S -> S[indexpids(S):2:length(S)] = repeat([myid()], length(indexpids(S):2:length(S))))
10-element SharedArray{Int64,1}:
 2
 3
 2
 3
 2
 3
 2
 3
 2
 3

In other words, you can have each worker access particular elements based on their id (returned by myid())

3

I would rather use DistributedArrays due to performance, SharedArrays make a copy to hard disk, while DistributedArrays work from memory.

4

Really? If you don’t create a SharedArray backed by a file (via SharedArray(file, type, dims) ), then I don’t see why the disk would be used. I’ve had good results with SharedArrays, in my limited experience.

5

In any case the question might be pertinent for HPC environments where users aren’t using shared memory

6

Idiot reply from me. Is there a way to reshape the original array such that the even and odd elements appear to be contiguous columns?

I guess I am asking this in a blue sky fashion in general for arrays, which might be interesting.