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<TITLE>Preconditioners - PC</TITLE>
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<H2> Preconditioners - PC: <A HREF="PETSC_DIRsrc/ksp/pc/examples/tutorials/index.html">Examples</A></H2>

The
<A HREF="PETSC_DIRdocs/manualpages/KSP/index.html">Scalable Linear Equations Solvers (KSP)</A>
component provides an easy-to-use interface to the combination of
a Krylov subspace iterative method and a preconditioner (in the
<A HREF="PETSC_DIRdocs/manualpages/KSP/index.html">KSP</A> and PC
components, respectively) or a sequential direct solver.  
KSP users can set various preconditioning
options at runtime via the options database (e.g., 
<font face ="Courier">
-pc_type jacobi
</font face>
).  
KSP users can also set PC options directly in application
codes by first extracting the PC context from the KSP context via
<A HREF="PETSC_DIRdocs/manualpages/KSP/KSPGetPC.html">KSPGetPC()</A>
and then directly calling the PC routines listed below (e.g., 
<A HREF="PETSC_DIRdocs/manualpages/PC/PCSetType.html">PCSetType()</A>
).
PC components can be used directly to create and
destroy solvers; this is not needed for users but
is for library developers.

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