Re: [ublas] how to iterate over the elements of a mapped_matrix ?

Subject: Re: [ublas] how to iterate over the elements of a mapped_matrix ?
From: Riccardo Rossi (rrossi_at_[hidden])
Date: 2011-02-08 02:40:31

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
>         
>         
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