Re: Stack size bugs and parisizemax

[Jeroen Demeyer <jdemeyer@cage.ugent.be>]

On 2015-01-20 21:32, Bill Allombert wrote:
> The purpose of parisizemax was to allow to have a nearly unlimited stack
> (limited only by the available hardware) without increasing the actual
> memory usage (in the sense that the final stack size will be close to the
> minimum stack size for which the computation would have succeed, up to a factor
> of two).
I don't think that parisizemax should behave like that. If an algorithm 
can work significantly faster by using a larger stack size than the 
minimum, it should do that.

> I assume you would still like to call gerepileall() when parisize reaches
> parisizemax, otherwise you will get a stack overflow.
Of course. In my proposal, if parisize == parisizemax, then the current 
behaviour remains. If parisize < parisizemax, then the number of GC's is 
limited.

> Your proposed change would cause the stack to fill up quickly to parisizemax
No, the stack size would still be bounded independent of parisizemax.

I implemented my proposal for determinant (PARI bug #1655) in Sage:
http://git.sagemath.org/sage.git/tree/build/pkgs/pari/patches/det_garbage.patch?id=5cd1f002e107df3d7ceadf71e89188f6776676af
This works perfectly: it doesn't cause an explosion of the stack Sage 
and it doesn't cause an unwanted slowdown. This patch was written for 
the 2.7 stack model, so it doesn't take into account parisizemax.


Cheers,
Jeroen.