>
>
>
> The possibility to use PCFIELDSPLIT (Matrix is
> stored as interlaced) has already been implemented in my
> solver program,
> but I am not sure on how to choose the parameters.
>
>
> What do you mean? Is your matrix defined to have a block size of 4, or
> have you set the IS's for each split (u,v,w,p)?
I used
CALL PCFieldSplitSetIS(PRECON,PETSC_NULL_CHARACTER,ISU,IERR)
...
The matrix is created as AIJ, but BAIJ with block size of 4 is also
possible (though not used as you can see from the output)
> The options for fieldsplit will be different depending on the answer.
>
>
> Before discussion any options for fielldsplit, what is App?
>
> Is that an approximate pressure Schur complement?
Sorry. A_ij, where i,j \in {u,v,w,p}, refers to the block matrices for
each variable and the respective coupling matrices to the other
variables. E.g.
- A_pp is defined as the matrix resulting from the discretization of the
pressure equation that considers only the pressure related terms.
- A_up is defined as the matrix resulting form the discretization u
momentum balance that considers the u-velocity-to-pressure coupling
(i.e. the discretized x component of the pressure gradient)
Note that the matrix is not stored as this, since I use field
interlacing.
>
>
> Cheers,
>
> Dave
>
>
> Each field corresponds to one of the variables (u,v,w,p).
> Considering
> the corresponding blocks A_.., the non-interlaced matrix would
> read as
>
> [A_uu 0 0 A_up]
> [0 A_vv 0 A_vp]
> [0 0 A_ww A_up]
> [A_pu A_pv A_pw A_pp]
>
> where furthermore A_uu = A_vv = A_ww. This might be considered
> to
> further improve the efficiency of the solve.
>
> You find attached the solver output for an analytical test
> case with 2e6
> cells each having 4 degrees of freedom. I used the
> command-line options:
>
> -log_summary
> -coupledsolve_ksp_view
> -coupledsolve_ksp_monitor
> -coupledsolve_ksp_gmres_restart 100
> -coupledsolve_pc_factor_levels 1
> -coupledsolve_ksp_gmres_modifiedgramschmidt
>
> Regards,
> Fabian Gabel
>
>
>
