# KSPTFQMR#

A transpose free QMR (quasi minimal residual),

## Notes#

Supports left and right preconditioning, but not symmetric

The “residual norm” computed in this algorithm is actually just an upper bound on the actual residual norm. That is for left preconditioning it is a bound on the preconditioned residual and for right preconditioning it is a bound on the true residual.

## References#

• **** -*** Freund, 1993

KSP: Linear System Solvers, KSPCreate(), KSPSetType(), KSPType, KSP, KSPTCQMR