dolfin team mailing list archive

[jesperc <jesperc@xxxxxx>]

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();

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
> > _______________________________________________
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