Re: debugging memory usage

Thanks Bart! You suggestions sound very useful, independently of my particular program. I'll try them & report on the outcome.

I've solved the overall problem by modifying the program such that it computes in a different way, which does not produce a memory exception on the examples I've tried.

Best regards,

Andrey


Bart Demoen wrote:
Andrey Rybalchenko wrote: 
Dear group,

my sicstus prolog program, which implements some symbolic computations,
terminates with the exception resource_error(0,memory).
The behavior is reproducible, but takes about 10 hours to do so.

What is the best way to find out where the memory is consumed? 

The "best" way might depend on how big your program is: if it not too
big, I would do a visual inspection looking for left behind
choicepoints, left recursion, and accumulating parameters that keep
accumulating during 10 hours. I would also look for creation of new
atoms/functors. If you know your program very well, you could do that
on a larger program as well.

Another thing you could do: call statistics/0 when you get the
exception. Any memory area that has grown will show up there.
If you feel unsure about that, try to get out of memory with
the following program:

a([X|R]) :-
        X = [1,2,3,4,5,6,7,8,9,0,_],
        a(R).

a :- a, b.

d :- d.
d.

once with the query ?- a(_).
and once with ?- a.
and once with ?- d.
and look at the output of statistics/0 and which areas have become big.
Compare it to what statistics shows after your own program has run out
of memory. You might not have learned very much, but at least you might
know whether the overflow is because of term creation, choicepoints or
recursion depth.

If the program is not too big, put it on a website so that we can see
it.

Tell us about the outcome please :-)

Cheers

Bart Demoen 
.

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