dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

No, that won't work. What the set() function does is

for i < num_rows:
  for j < num_cols:
    A[rows[i], cols[j]] = vals[i*num_rows + j]

So, the length for vals needs to be num_rows*num_cols.

To create an identity matrix, it should be enough to do

Matrix A(N, N);
unsigned int rows[N];
for (unsigned int i = 0; i < N; i++)
    rows[i] = i;
A.ident(rows, N);
A.apply();

By the way, it looks like we need to change the order of arguments in 
the ident function. The size argument should come before the array 
argument (same as in PETSc and many other libraries). We have changed 
this for add(), set(), get() but forgot to fix it for ident(). So watch 
out for the change of order in parameters...

/Anders


Mads Hoel wrote:
> I think so, but maybe the experts should answer. :P
>
> Regards,
> Mads Hoel
>
> ------- Forwarded message -------
> From: jesperc <jesperc@xxxxxx>
> To: "Mads Hoel" <mfhoel@xxxxxxxxxx>
> Cc:
> Subject: Re: [DOLFIN-dev] Identity matrix
> Date: Wed, 18 Jul 2007 16:29:43 +0200
>
> Hi,
>
> Yes, I see that this has changed in the new version but I still use the
> old one.
> However, I see now that the number of columns and rows can be different
> which indicates that set() may work in another way than I thought.
> Doesn't val={1,2}, col={3,4}, row={5,6} mean that element (5,3) is 1 and
> element (6,4) is 2?
>
> Regards, Jesper
>
> Mads Hoel skrev:
> > On Wed, 18 Jul 2007 15:56:48 +0200, jesperc <jesperc@xxxxxx> wrote:
> >
> > > A->set(vals, cols, n, rows, n);
> > void     set (const real *block, uint m, const uint *rows, uint n, const  
> > uint *cols)
> >      Set block of values.
> >
> > I think you need to rearrange the parameters
> >
> > A->set(vals, cols, n, rows, n); to A->set(vals, n, rows, n, cols);
> >
> > Regards,
> > Mads Hoel
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