[petsc-users] Sparse Approximate Inverse (SPAI) preconditioner

[Barry Smith]

On May 12, 2011, at 10:33 AM, Danesh Daroui wrote:

> 
> Hi,
> 
> I am using PETSc to solve a linear system of complex double precision
> data type. I intend to use SPAI preconditioner to solve the equation and
> I know that SPAI is not supported with complex systems. Since I have
> imaginary values only on diagonal, so according to my tests, approximate
> inverse of only real part of the coefficient matrix is a good
> preconditioner for my need. Therefore, I would like to install SPAI with
> PETSc and use it just to calculate approximate inverse of the real part
> of the matrix which should be possible. The problem is that PETSc can be
> configured to install SPAI when complex solver is being installed or I
> don't know how! The other questions that, is there any way to store the
> complex matrix in PETSc (like I do) and pass only real part of it to the
> routine which calculates approximate inverse? Otherwise I need to store
> both complex and real values which will eat up the memory.

   No. PETSc either works with all objects as real. Or all objects as complex. There is no way to do some computations with real and others with complex.

   Barry

> 
> Regards,
> 
> Danesh
> 
>