[Caml-list] Native code and stack limit

[Caml-list] Native code and stack limit

[Berke Durak]

Some people in my lab complained of not being able to use Ocaml for depth-first
exploring graphs with 1,000,000 or so nodes. Of course the usual remarks about
tail recursion and stack limit have been raised. I decided to check these claims
so I made a small program to depth-first search a random graph with about
80 bytes of intermediary data per node. Including stack space overhead for
some function calls, I think the whole graph sould be explorable in less than
100 * n bytes stack space (rough guess).

It seems that when compiling to native code, the run-time library ignores
both the OCAMLRUNPARAM="l=256M" and Gc.set {(Gc.get()) with Gc.stack_limit
= 64 * 1024 * 1024} instructions. The native-code program systematically aborts
when its process size reaches 64M. I took a look at asmrun/gc_ctrl.c and
the code for adjusting stack size is preprocessed-out. I also have no ulimits
on my machine. Further, running the following code with OCAMLRUNPARAM="l=256M,v=8"

let _ = Gc.set {(Gc.get()) with Gc.stack_limit = 64 * 1024 * 1024}

prints an

Initial stack limit: 1024k bytes
Changing stack limit to 262144k bytes

only if compiled to byte code.

Is there a problem here ? Am I missing something ? I've searched the mailing
list and the frequently asked questions. There's nothing about Stack_overflow
with native code.

Thanks for your help.
-- 
Berke Durak
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Re: [Caml-list] Native code and stack limit

[Berke Durak]

On Tue, Sep 10, 2002 at 02:43:22PM +0200, Berke Durak wrote:
> I also have no ulimits on my machine.

Sorry I had an 8Mb limit on my stack. I thought "ulimit" would show all
limits. Not.  Shame on me.

I have also checked the latest CVS sources ; it seems that there are no
more references to the stack limit in asmrun.

May I suggest fixing the documentation as follows :
In the native-code compilation section, specify which OCAMLRUNPARAM options
are used ; stress that there is no Ocaml-imposed stack limit, that the stack
limit can be checked (at least under Linux) using "ulimit -a" and be set using
"ulimit -s", and that a stack overflow throws a Stack_overflow exception.

Would it be a luxury if the native startup code complained if the
OCAMLRUNPARAM-specified stack limit exceeds the system stack limit ?
-- 
Berke Durak
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Re: [Caml-list] Native code and stack limit

[M E Leypold @ labnet]

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