# Linear Solvers and Krylov Methods (KSP)
The `KSP` class provides an easy-to-use interface to the combination of
a Krylov subspace iterative method and a preconditioner `PC` for the solution of linear systems and some least squares problems. See
`PETSCREGRESSORLINEAR` for additional regression (least squares) solvers.
Examples
Source files
bddcnullspace.c
bddc.c
bddcfetidp.c
bddcgraph.c
bddcprivate.c
bddcscalingbasic.c
bddcschurs.c