How to sum multidimensional arrays?

[p.shkadzko]

On Thursday, 27 February 2020 at 14:15:26 UTC, p.shkadzko wrote:
> This works but it does not look very efficient considering we 
> flatten and then calling array twice. It will get even worse 
> with 3D arrays.

And yes, benchmarks show that summing 2D arrays like in the 
example above is significantly slower than in numpy. But that is 
to be expected... I guess.

D -- sum of two 5000 x 6000 2D arrays: 3.4 sec.
numpy -- sum of two 5000 x 6000 2D arrays: 0.0367800739913946 sec.