* Strange memory leak
@ 2001-02-09 21:08 Hao-yang Wang
0 siblings, 0 replies; 2+ messages in thread
From: Hao-yang Wang @ 2001-02-09 21:08 UTC (permalink / raw)
To: caml-list
I wrote this bunch of code:
-----------------------------------
type 'a zlist = Znull | Zcons of 'a * 'a zzlist
and 'a zzlist = 'a zlist Lazy.t
let rec zfilter f zz =
let z = Lazy.force zz in
match z with
Znull ->
Znull
| Zcons(head, ztail) ->
if f head then
z
else
zfilter f ztail
let rec build_list n =
if n > 0 then
Zcons(n, lazy (build_list (n - 1)))
else
Znull
let rec loopy f zz =
match zfilter f zz with
Znull ->
()
| Zcons(head, ztail) ->
loopy f ztail
-----------------------------------
>From the byte-code toplevel, the following expression evaluates fine
loopy (fun x -> true) (lazy (build_list 1000000));;
while the following expression produces "Fatal error: out of memory."
loopy (fun x -> false) (lazy (build_list 1000000));;
Why? In particular, the function zfilter looks tail-recursive to me.
I am using ocaml-3.00, with the Macintosh version of top-level.
Thanks,
Hao-yang Wang
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: Strange memory leak
@ 2001-02-09 23:41 Hao-yang Wang
0 siblings, 0 replies; 2+ messages in thread
From: Hao-yang Wang @ 2001-02-09 23:41 UTC (permalink / raw)
To: caml-list
After I posted the last message, I think I have found out what's wrong.
In the function 'loopy', when it calls into 'zfilter f zz', the variable
zz keeps holding the head of the lazy list, thus prevents GC from
reclaiming the memory.
Still, I don't know how to rewrite loopy to plug this leak. Any help?
Thanks,
Hao-yang Wang
>I wrote this bunch of code:
>-----------------------------------
>type 'a zlist = Znull | Zcons of 'a * 'a zzlist
>and 'a zzlist = 'a zlist Lazy.t
>
>let rec zfilter f zz =
> let z = Lazy.force zz in
> match z with
> Znull ->
> Znull
> | Zcons(head, ztail) ->
> if f head then
> z
> else
> zfilter f ztail
>
>let rec build_list n =
> if n > 0 then
> Zcons(n, lazy (build_list (n - 1)))
> else
> Znull
>
>let rec loopy f zz =
> match zfilter f zz with
> Znull ->
> ()
> | Zcons(head, ztail) ->
> loopy f ztail
>-----------------------------------
>From the byte-code toplevel, the following expression evaluates fine
>
> loopy (fun x -> true) (lazy (build_list 1000000));;
>
>while the following expression produces "Fatal error: out of memory."
>
> loopy (fun x -> false) (lazy (build_list 1000000));;
>
>Why? In particular, the function zfilter looks tail-recursive to me.
>
>I am using ocaml-3.00, with the Macintosh version of top-level.
>
>Thanks,
>Hao-yang Wang
^ permalink raw reply [flat|nested] 2+ messages in thread
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