On Tue, 26 Feb 2019 at 17:01, Vincent Delecroix <20100.delecr...@gmail.com>
wrote:
> I don't think this has ever been implemented in Sage. You
> have to figure out how to create a sparse matrix in magma
> and write Sage code to produce it. You can get inspiration
> from the current code of _magma_init_
>
> def _magma_init_(self):
> P = magma(self.parent())
> v = [x._magma_init_(magma) for x in self.list()]
> return '%s![%s]'%(P.name(), ','.join(v))
>
> Vincent
>
This would be a very useful addition (for some people). Magma constructs
sparse matrices using SparseMatrix() with several interfaces including
(m::RngIntElt, n::RngIntElt, Q::SeqEnum[Tup]) -> MtrxSprs
The m by n sparse matrix, whose entries are given by the tuples in
Q of the form <i, j, x> (specifying that x is at entry (i, j)).
Example:
> M:=SparseMatrix(3,3,[<1,1,1>,<2,2,1>,<3,3,1>]);
> IdentitySparseMatrix(Integers(), 3) eq M;
true
>
> Le 26/02/2019 à 17:55, Pierre Guillot a écrit :
> > Thanks! I think to know where the issue is :
> >
> > M= random_matrix(ZZ, 10, sparse= True, density= 0.1)
> > M._magma_init_(magma)
> >
> >
> '_sage_[11]![0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,-1,0,0,0,0,0,0,0,-1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,-14,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,8,0,0,0,0]'
> >
> >
> > This does not look like a sparse matrix to me : it's been converted to a
> > "dense" matrix before magma code was produced...
> >
> > no wonder if my 50,000 x 50,000 matrix takes forever to load...
> >
> > If anyone has an easy fix, it would be great. Otherwise, i'll have to
> learn
> > the syntax for sparse matrices in magma, and figure out how magma reads
> > from a file...
> >
> >
> >
> >
> >
> >
>
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