Re: qflllgram

[Igor Schein <igor@txc.com>]

On Mon, Feb 27, 2006 at 01:34:11AM -0500, Gonzalo Tornaria wrote:
> Strange behaviour:
> 
> ? qflllgram([1,0;0,-1],0)
>   *** qflllgram: the PARI stack overflows !
>   current stack size: 128000000 (122.070 Mbytes)
>   [hint] you can increase GP stack with allocatemem()
> 
> ? allocatemem()
>   *** allocatemem: Warning: doubling stack size; new stack = 256000000
> (244.141 Mbytes).
> ? qflllgram([1,0;0,-1],0)
>   *** qflllgram: length (lg) overflow
> ? \v
>               GP/PARI CALCULATOR Version 2.2.12 (development CHANGES-1.1453)
>                 i686 running linux (ix86/GMP-4.1.4 kernel) 32-bit version
>                    compiled: Jan 21 2006, gcc-3.3.5 (Debian 1:3.3.5-13)
>                      (readline v5.0 enabled, extended help available)
> 
> It /does/ work with flag=1 (lllgramint):
> 
> ? qflllgram([1,0;0,-1],1)
>   *** qflllgram: not a definite matrix in lllgram
> 
> Best, Gonzalo

I also have a question stemming from this behavior.  Is the first
argument a valid input?  It's definitely symmetric, but does it
correspond to a positive definite quadratic form, like the manual
requires?  In general, what's the command to convert t_QFI to t_MAT
and vice versa?  If it's answered somewhere in the manual, then I am
sorry for not finding it myself; if it isn't, it might be FAQ-worthy.

Thanks

Igor