On 5 March 2013 06:54, Peng Tian <tianpeng.ch...@gmail.com> wrote:
> Dear David,
> You are right. I tried to change the data type of the code in sage, which is
> "int" type in the source code of SAGE and now I'm using "long int" instead.
> The previous error is gone and everything is working well now.
>
> Thanks a lot!
>
> Best regards!
> Peng
>
Dear Peng,
Using long ints is a sound temporary fix, I guess. It would have the
side-effect of making the small N cases slightly slower and more
memory-hungry, so it might be best to have two separate functions in
the code, one using ints and the other longs, and choose between them
according to whether N^2 > 2^{31} or not; we already do similar things
for some other related functions, e.g lift_to_sl2z(). You could even
write a patch for this and upload it to Sage's trac server; then
that'll prevent anyone else having this problem in the future.
In an ideal world we'd also want a third implementation that uses MPIR
arbitrary-precision integers; this will be necessary when N is
*really* big, i.e. N^2 > 2^{63}. But I suspect that nobody's going to
be calculating Heilbronn matrices for such big N for a long while yet.
David
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