On Tue, Jun 23, 2009 at 4:30 PM, William Stein<wst...@gmail.com> wrote:
> 2009/6/23 Emmanuel Thomé <emmanuel.th...@gmail.com>:
>>
>>
>> I wonder what happens here:
>>
>> tiramisu ~ $ sage
>> ----------------------------------------------------------------------
>> | Sage Version 4.0, Release Date: 2009-05-29 |
>> | Type notebook() for the GUI, and license() for information. |
>> ----------------------------------------------------------------------
>> sage: p=3
>> sage: n=1000
>> sage: K=GF(p)
>> sage: KP.<x>=PolynomialRing(K)
>> sage: MS=MatrixSpace(K,n,n);
>> sage: A=MS.random_element()
>> sage: MSP=MatrixSpace(KP,n,n);
>> sage: time xI=x*MSP.identity_matrix()
>> CPU times: user 17.37 s, sys: 0.15 s, total: 17.52 s
>> Wall time: 17.54 s
>> sage: time xI=diagonal_matrix([x for i in range(n)])
>> CPU times: user 32.18 s, sys: 0.14 s, total: 32.33 s
>> Wall time: 32.34 s
>> sage: time xI.determinant()
>> <got fed up before it finishes...>
>>
>
> Type xl.determinant?? to see:
>
> ..
> # fall back to very very stupid algorithm -- expansion by minors.
> # TODO: surely there is something much better, even in total
> generality...
> # this is ridiculous.
> d = self._det_by_minors(self._ncols)
> self.cache('det', d)
> return d
>
Sorry, but it almost goes without saying...
"implement it and post a patch!"
--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to sage-support@googlegroups.com
To unsubscribe from this group, send email to
sage-support-unsubscr...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/sage-support
URLs: http://www.sagemath.org
-~----------~----~----~----~------~----~------~--~---
