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[Nuno David Lopes <ndl@xxxxxxxxxxxxxx>]

The problem persists.

shouldn't this code produce exactly the same results,
 when we change the comments between line marked with (1) and (2) :
(using uBLAS backend)

-----------------------------------------------------------------------------
....
LUSolver solver_dvg;
.....
 // {{{ (22.29) BUG RELATED WITH THIS STEP
  Matrix A_dvg; 
  Vector b_dvg; 
  assemble(A_dvg,a_dvg,mesh);
  //solver_dvg.factorize(A_dvg);                 (1)
  assemble(b_dvg,L_dvg,mesh);
  bc0.apply(A_dvg,b_dvg,a_dvg); 
  //solver_dvg.factorized_solve(x_r,b_dvg); (1)
  solver_dvg.solve(A_dvg,x_r,b_dvg);         (2)
...
// {{{ LOOP 
do{
....
      // {{{ (22.34) BUG RELATED WITH THIS STEP
      assemble(b_dvg,L_dvg,mesh);
      //solver_dvg.factorized_solve(x_bar_r,b_dvg); (1)
      solver_dvg.solve(A_dvg,x_bar_r,b_dvg);         (2)
      // }}}
....
    // {{{ERROR EVALUATION
     ...
    // }}}
....
}while(iter<MAXITER)
// }}}

Note that after the changes in Umfpack uBLAS, the ERROR evalution was the 
same.
Now i've got after 2 iterations  
>>>>>>>>>LOOP ERROR=6342.645308 (Factorized case)
>>>>>>>>>LOOP ERROR=1.547989 (non-factorized, petsc, before changes)
when i look to the solutions i've got diferences in the pressure essentially 
in problematic points near the corners.

Thanks in advance.

On Friday 05 September 2008, Nuno David Lopes wrote:
> I'm not able to see problems for instance in the convection-diffusion demo,
> after 38 steps.
> So i'll guess that reducing it to a small problem to find the bug will not
> be easy.
>
> I will try to clean and comment a little more my code, and if i find that
> i'm not doing something really stupid, and if the bug persists i'll send my
> code. It's a   3D stokes  problem with taylor-hood  elements solved by an
> uzawa algorithm.
>
> On Thursday 04 September 2008, Garth N. Wells wrote:
> > Can you send an example that reproduces the problem? Say for a 2x2
> > matrix?
> >
> > Garth
> >
> > Nuno David Lopes wrote:
> > > I guess there is a bug on
> > > factorize, factorized_solve....factorizedSolve or in some related
> > > function.
> > >
> > > Some of my results with factorize and factorized_solve, before
> > > UmfpackLUSolver and uBlas->uBLAS changes, are completely different from
> > > the new ones.
> > >
> > > I've tested with PETSc, and with uBLAS without factorization and I've
> > > recovered the good solutions.



-- 
Nuno David Lopes

e-mail:ndl@xxxxxxxxxxxxxx        (FCUL/CMAF)
           nlopes@xxxxxxxxxxxxxxx    (ISEL)
http://ptmat.ptmat.fc.ul.pt/%7Endl/ 

Fri Sep  5 14:52:44 WEST 2008