# KSPCGS#

This code implements the CGS (Conjugate Gradient Squared) method.

## Notes#

Does not require a symmetric matrix. Does not apply transpose of the matrix.

Supports left and right preconditioning, but not symmetric.

## Developer Note#

Has this weird support for doing the convergence test with the natural norm, I assume this works only with no preconditioning and symmetric positive definite operator.

## References#

• **** -*** Sonneveld, 1989.

KSP: Linear System Solvers, KSPCreate(), KSPSetType(), KSPType, KSP, KSPBCGS, KSPSetPCSide()