> In a traditional language, I'd have a mapping - something like the
> following pseudo-code.
>
> result = {}
> do 1000000 times:
> newval = verb()
> result[newval] = result[newval] + 1 # Needs a special case for the
> first time we see a value.
OK, it sounds like you're looking for a hashmap/hashtable/associative
array/dictionary
Here is one implementation in J:
https://github.com/jonghough/msgpack-j/blob/master/hashmap.ijs
Or http://code.jsoftware.com/wiki/Essays/DataStructures#Associative_Array
On Tue, Feb 21, 2017 at 8:41 AM, Paul Moore <[email protected]> wrote:
> On 21 February 2017 at 13:23, Joe Bogner <[email protected]> wrote:
> >>
> >> The key thing here is that I'm going to be collecting millions of
> >> results, and I'll run out of memory if I just retain them all and
> >> count at the end. But I'm not sure how to modify structures in J.
> >>
> >
> > Are you sure you will run out of memory? I can hold a billion ints on my
> > machine and use 7.8gb of memory.
>
> I did yesterday. I can't recall the details - I may have been running
> a billion simulations. I may well also have been using a
> memory-inefficient approach, though (if I held 5 numbers for each run,
> that would be 40GB of RAM I guess).
>
> My purpose behind this exercise is that I'm trying to demonstrate to a
> friend that you don't need to write custom C programs (which is what
> he did) to do this type of work, and that off the shelf (albeit
> specialised) languages can cope fine (where "fine" means "comparable
> to custom C"). So far, I'm finding that's not true - my experiments
> with various languages[1] have either been too slow or too memory
> hungry to make my case. When a tiny performance issue or over-use of
> memory in the implementation of the single experiment gets multiplied
> by factors on the order of millions or billions, that doesn't scale
> well enough.
>
> It's an interesting exercise that's got me learning a lot about
> various languages' strengths and weaknesses, though :-)
>
> Paul
>
> [1] Most of which have been at the "interested beginner" level, as here.
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
>
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
