[petsc-users] schurcomplement of a rectangular system

[Barry Smith]

  I have put this into the branches barry/allow-nonsquare-schurcomplement and next

   Barry

> On Nov 11, 2014, at 8:51 AM, Patrick Lacasse <patrick.m.lacasse at gmail.com> wrote:
> 
> Hi,
> 
>   in my works, I'm computing a formula (involving an L2 projection) of the form:
> 
> (D - M^{-1} N) n
> 
> where D,M and B are matrices and n is a vector.
> 
> Operator (D - M^{-1} N) appears to be the Schur complement of the system
> ( M   N )
> (  I    D )
> and it is convenient for me to use a Mat of type schurcomplement to compute it.
> However, my matrix D is not a square matrix (this system is not invertible, it is rectangular).
> 
> Assertions in src/ksp/ksp/utils/schurm.c prohibit the use of schurcomplement for rectangular system, but I can't figure where it is needed by schurcomplement itself.
> Could it be possible to remove those two assertions (see my patch)?
> 
> 
> Patrick Lacasse
> <0001-Remove-an-assertion-in-MatSchurComplement.patch>