On 2/21/07, Iftikhar Burhanuddin <[EMAIL PROTECTED]> wrote:
>
> Hi folks,
>
> Random sparse matrices over finite fields generated by SAGE do not look
> sparse to me. Bug?
>
> sage: Mat(GF(17), 10, sparse=True).random_element()
Ifti,
looking at the docs for random_element(), it looks like you need to
specify another argument to get a sparse matrix:
{{{
sage: MS = MatrixSpace(ZZ,10,sparse=True); MS.random_element (density=0.4)
[ 0 0 0 0 0 0 -2 -1 0 0]
[ 0 0 0 1 -2 0 0 0 0 0]
[-2 1 0 0 0 0 0 0 2 0]
[ 0 -2 1 2 -2 0 0 0 0 0]
[ 2 0 0 2 0 0 2 0 -1 0]
[ 0 0 0 0 1 0 -2 -1 -1 0]
[ 2 0 2 0 0 0 0 2 0 -2]
[ 0 -1 0 0 0 2 -2 0 -1 0]
[ 0 0 0 0 0 2 0 0 0 2]
[ 0 0 0 -2 0 -2 0 2 -1 1]
}}}
This seems somewhat counter-intuitive to me. Maybe there should be a
self._density that gets set to something like 0.3 when
self.__is_sparse is True?
Another idea: maybe we should be able to set the density directly:
{{{
MS = MatrixSpace(ZZ,10,sparse=True,density=0.4)
}}}
although this seems redundant to me...
didier
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