dolfin team mailing list archive

["Garth N. Wells" <g.n.wells@xxxxxxxxxx>]

jesperc wrote:
> Hi again,
>
> I realize that assigning values blockwise is more efficient but if I try 
> the following I get a segmentation fault (it works for one single 
> row/column at a time though):
>
> Matrix A;
> A.init(n,n,1);
> real *vals = new real[n];
> int *cols = new int[n];
> int *rows = new int[n];
> for (int i=0; i<n; ++i)
>   {
>    vals[i] = 1.0;
>    cols[i] = i;
>    rows[i] = i;
>   }
> A->set(vals, cols, n, rows, n);
> A->apply();


I don't know what's going on. You could try

  A.init(n, n, 2);

If you can test against the development version of DOLFIN and still have 
a problem, I can take a look at it.

Garth

> Regards, Jesper
>
> Garth N. Wells skrev:
> > jesperc wrote:
> > > Hi,
> > >
> > > Does anyone have an example of using the ident() function in 
> > > PETScMatrix. I cannot get it to work 
> > Matrix::ident(. . . ) is not meant to do this, so it is unlikely to work.
> >
> > and using a for loop with set() to
> > > create an identity matrix is painfully slow...
> > >
> > > This is how I do it now:
> > >
> > > Matrix A;
> > > A.init(n,n,1);
> > > for (int i=0; i<n; ++i)
> > >    A.set(i,i,1);
> > You shouldn't set Matrix values element-wise 
> > (Matrix::set(int,int,real) has been removed from the Matrix interface 
> > to stop users doing this). If you really want to access matrix entries 
> > element-wise, use a uBlasMatrix, otherwise set values in large blocks 
> > using
> >
> >   Matrix::set(const real* block, uint m, const uint* rows, uint n, 
> > const uint* cols)
> >
> > Garth
> >
> > > and it kills me/my computer.
> > >
> > > Kind regards, Jesper
> > > _______________________________________________
> > > DOLFIN-dev mailing list
> > > DOLFIN-dev@xxxxxxxxxx
> > > http://www.fenics.org/mailman/listinfo/dolfin-dev
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