Question

I have just started learning Erlang and am trying out some Project Euler problems to get started. However, I seem to be able to do any operations on large sequences without crashing the erlang shell.

Ie.,even this:

list:seq(1,64000000). 

crashes erlang, with the error:

eheap_alloc: Cannot allocate 467078560 bytes of memory (of type ‘heap’).

Actually # of bytes varies of course.

Now half a gig is a lot of memory, but a system with 4 gigs of RAM and plenty of space for virtual memory should be able to handle it.

Is there a way to let erlang use more memory?

Answer 1

Your OS may have a default limit on the size of a user process. On Linux you can change this with ulimit.

You probably want to iterate over these 64000000 numbers without needing them all in memory at once. Lazy lists let you write code similar in style to the list-all-at-once code:

-module(lazy). -export([seq/2]).  seq(M, N) when M =< N ->     fun() -> [M | seq(M+1, N)] end; seq(_, _) ->     fun () -> [] end.  1> Ns = lazy:seq(1, 64000000). #Fun<lazy.0.26378159> 2> hd(Ns()). 1 3> Ns2 = tl(Ns()). #Fun<lazy.0.26378159> 4> hd(Ns2()). 2