|
|
Ublas : |
Subject: Re: [ublas] how to iterate over the elements of a mapped_matrix ?
From: Sunil Thomas (sgthomas27_at_[hidden])
Date: 2011-02-08 02:53:03
Thats from my code. But I remember spending several hours
reading their web pages on sparse matrices before I could figure
out how to use it.
I cannot remember the link.. you can try googling it. But I do
admit that boost docs are very difficult to find and obscure in
terms of examples. Maybe it is better now.
You can try this for example:
http://www.boost.org/doc/libs/1_45_0/libs/numeric/ublas/doc/matrix_sparse.htm
http://www.guwi17.de/ublas/examples/
--Thomas.
On Mon, Feb 7, 2011 at 11:40 PM, Riccardo Rossi <rrossi_at_[hidden]>wrote:
>
> Hello Thomas,
> thank you for the snippet but...where did u take it from? i was
> looking for the documentation but i could not find it. Could u pass me
> the pointer for the future?
>
> thanks
> Riccardo
>
>
>
> On Mon, 2011-02-07 at 17:51 -0800, Sunil Thomas wrote:
> > Hi Riccardo,
> >
> > This follows straight from the ublas docs and examples
> > therein..here's a snippet that may help:
> >
> >
> > for(itm1 i1 = A.begin1(); i1 != A.end1(); ++i1) {
> > int nnz = 0;
> > itm2 i2 = i1.begin();
> > irow = (int) i2.index1();
> > //Loop over each row's non-zero elements
> > for(; i2 != i1.end(); ++i2) {
> > (m_cols)[nnz] = (int) i2.index2();
> > (m_vals)[nnz] = *i2;
> > ++nnz;
> > }
> > //-Some treatment of zero rows...
> > if( nnz == 0 ) {
> > (m_cols)[nnz] = irow;
> > (m_vals)[nnz] = -1.0;
> > ++nnz;
> > }
> > //-Do other stuff...blah blah
> > }
> >
> > --Thomas.
> >
> >
> >
> > On Mon, Feb 7, 2011 at 10:13 AM, <rrossi_at_[hidden]> wrote:
> > Dear list,
> >
> > i created a mapped_matrix and now i need to
> > iterate over the non_zero elements of SOME rows.
> >
> > say i need all of the elements of row 123... how should i get
> > them?
> >
> >
> >
> > thanks in advance
> >
> > Riccardo
> >
> >
> > _______________________________________________
> > ublas mailing list
> > ublas_at_[hidden]
> > http://lists.boost.org/mailman/listinfo.cgi/ublas
> > Sent to: sgthomas27_at_[hidden]
> >
> > _______________________________________________
> > ublas mailing list
> > ublas_at_[hidden]
> > http://lists.boost.org/mailman/listinfo.cgi/ublas
> > Sent to: rrossi_at_[hidden]
>
> _______________________________________________
> ublas mailing list
> ublas_at_[hidden]
> http://lists.boost.org/mailman/listinfo.cgi/ublas
> Sent to: sgthomas27_at_[hidden]
>