[Jprogramming] J v NumPy (was Re: J v Python)

[Konrad Hinsen]

--On 13 décembre 2012 10:45:42 -0500 Raul Miller <rauldmiller at gmail.com> 
wrote:

> Copying is an easy operation, and if you are doing any significant
> work the cost of a copy is often trivial when compared with everything
> else you are doing.

Except for arrays that take up half of my machine's RAM.

> The result of 3!:1 is very close to the internal representation.  That
> said, if you look in jtype.j in the j source, you'll see this:
>
> :typedef struct {I k,flag,m,t,c,n,r,s[1];}* A;
>
> along other supporting declarations (note especially the section
> marked "Fields of type A") -- that's the internal representation of
> J's arrays.

OK, that looks quite close in spirit (though not in layout) to NumPy 
arrays. It should be possible to wrap a J array in a Python buffer object 
and create a NumPy array on top of that. Then we would have a J array and a 
NumPy array with shared data space, readable and writable (with care!) from 
both sides.

That leaves the question of how to make Python and J live in the same 
address space. I am sure it can be done, but I suspect it's not trivial. 
Python embedded into the J interpreter is one option, but if the inverse is 
doable, it's probably easier.

Konrad.