Re: [sage-devel] libpari defaults
On Fri, 4 Jan 2019 at 10:21, Jeroen Demeyer wrote:
> On 2019-01-04 10:22, John Cremona wrote:
> > Some of the runs I have been doing use a large amount of RAM and some
> > fail
>
> "fail" in which sense? I assume you mean a PariError saying that the
> stack overflowed but I can only guess...
>
Yes, that's right. Sorry not to be more explicit.
>
> > One is suppose to be able to increase this using the following syntax
> > sage: pari.default('parisizemax', 120)
> > but that raises a run-time error
>
> That error is actually a PARI "feature". It's one of the many curious
> implementation details of the PARI stack. The idea is that you shouldn't
> change the stack size during a computation. So the error forces the
> running computation to abort.
>
> In GP this error is silenced but you can still see its effect:
>
> gp> a=1; default(parisizemax, 10); a=2
>*** Warning: new maximum stack size = 101536 (953.676 Mbytes).
> gp> a
> %2 = 1
>
> Note that the "a=2" is not executed!
>
> Now to solutions: I would recommend using pari.allocatemem(sizemax=N) to
> change the stack size. That is handled a lot better by cypari2.
>
I will try that. However the last time this happened was after about 5
days of computation so testing is not so easy.
Thanks,
John
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Re: [sage-devel] libpari defaults
On 2019-01-04 10:22, John Cremona wrote:
Some of the runs I have been doing use a large amount of RAM and some
fail
"fail" in which sense? I assume you mean a PariError saying that the
stack overflowed but I can only guess...
One is suppose to be able to increase this using the following syntax
sage: pari.default('parisizemax', 120)
but that raises a run-time error
That error is actually a PARI "feature". It's one of the many curious
implementation details of the PARI stack. The idea is that you shouldn't
change the stack size during a computation. So the error forces the
running computation to abort.
In GP this error is silenced but you can still see its effect:
gp> a=1; default(parisizemax, 10); a=2
*** Warning: new maximum stack size = 101536 (953.676 Mbytes).
gp> a
%2 = 1
Note that the "a=2" is not executed!
Now to solutions: I would recommend using pari.allocatemem(sizemax=N) to
change the stack size. That is handled a lot better by cypari2.
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[sage-devel] libpari defaults
I have been making extensive use of the Sage interface to libpari (in work
I will be reporting on soon at the Pari workshop
http://pari.math.u-bordeaux.fr/Events/PARI2019/.
http://pari.math.u-bordeaux.fr/Events/PARI2019/
Some of the runs I have been doing use a large amount of RAM and some fail
even on a machine with 512GB. By default the size of the libpari parameter
'parisizemax' is half the physical RAM, for example on a 16GB laptop I see
sage: pari.default('parisizemax')
8324022272
while on the large machine I see
sage: pari.default('parisizemax')
272689184768
One is suppose to be able to increase this using the following syntax
sage: pari.default('parisizemax', 120)
but that raises a run-time error, even though afterwards:
sage: pari.default('parisizemax')
1202048
This is with 8.6.rc0.
I think it is a bug that there is a run-time error, and my question is
whether or not I can trust that the value has really changed?
John
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