dolfin team mailing list archive

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

On Sun, 2006-05-07 at 14:10 +0200, Anders Logg wrote:
> When adding the option to compile without PETSc, I took the
> opportunity change the precomputation of quadrature weights for the
> ODE solvers to use DenseMatrix instead of the standard PETSc
> Matrix. (The matrices are small and dense anyway.)
> 
> It seems that DenseMatrix::invert() sometimes gives unexpected results
> and the reason seems to be a memory access error somewhere in ublas. I
> don't know if this is a problem with ublas or the way we use
> it. Garth, could you look again at DenseMatrix::invert() and see if
> you can spot something obvious?
> 
> I have attached the error log from running valgrind and here is the code that
> reproduces the error:
> 
>    DenseMatrix A(3, 3);
>    A(0, 0) = A(1, 1) = A(2, 2) = 1.0;
>    A.invert();
> 

When you create a matrix, it is not initialised to zero by Boost. You
can do

    A.clear(); // the Boost function

or

    A = 0; // DOLFIN wrapper for A.clear() (provides compatibility with
Matrix, but I prefer A.clear() because A = x only works for x = zero.)

I left it up to the user to initialise the matrix because often all
values will be set by the user, so initialisation is just extra overhead
from some problems.

Garth

> How about adding solve(DenseVector& x, const DenseVector& b) to DenseMatrix?
> 
> /Anders
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-- 
Dr. Garth N. Wells
Faculty of Civil Engineering and Geosciences
Delft University of Technology
Stevinweg 1
2628 CN Delft
Netherlands

tel.     +31 15 278 7922
fax.     +31 15 278 6383
e-mail   g.n.wells@xxxxxxxxxx
url      http://www.mechanics.citg.tudelft.nl/~garth