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<div id="version" align=right><b>slepc-3.22.2 2024-12-02</b></div>
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<H1>STSetSplitPreconditioner</H1>
Sets the matrices from which to build the preconditioner in split form.
<H3><FONT COLOR="#883300">Synopsis</FONT></H3>
<PRE>
#include "slepcst.h"
<A HREF="https://petsc.org/release/manualpages/Sys/PetscErrorCode.html#PetscErrorCode">PetscErrorCode</A> <A HREF="../ST/STSetSplitPreconditioner.html#STSetSplitPreconditioner">STSetSplitPreconditioner</A>(<A HREF="../ST/ST.html#ST">ST</A> st,<A HREF="https://petsc.org/release/manualpages/Sys/PetscInt.html#PetscInt">PetscInt</A> n,<A HREF="https://petsc.org/release/manualpages/Mat/Mat.html#Mat">Mat</A> Psplit[],<A HREF="https://petsc.org/release/manualpages/Mat/MatStructure.html#MatStructure">MatStructure</A> strp)
</PRE>
Collective
<P>
<H3><FONT COLOR="#883300">Input Parameters</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>st </B></TD><TD> - the spectral transformation context
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>n </B></TD><TD> - number of matrices
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>Psplit </B></TD><TD> - array of matrices
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>strp </B></TD><TD> - structure flag for Psplit matrices
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#883300">Notes</FONT></H3>
The number of matrices passed here must be the same as in <A HREF="../ST/STSetMatrices.html#STSetMatrices">STSetMatrices</A>().
<P>
For linear eigenproblems, the preconditioner matrix is computed as
Pmat(sigma) = A0-sigma*B0, where A0 and B0 are approximations of A and B
(the eigenproblem matrices) provided via the Psplit array in this function.
Compared to <A HREF="../ST/STSetPreconditionerMat.html#STSetPreconditionerMat">STSetPreconditionerMat</A>(), this function allows setting a preconditioner
in a way that is independent of the shift sigma. Whenever the value of sigma
changes the preconditioner is recomputed.
<P>
Similarly, for polynomial eigenproblems the matrix for the preconditioner
is expressed as Pmat(sigma) = sum_i Psplit_i*phi_i(sigma), for i=1,...,n, where
the phi_i's are the polynomial basis functions.
<P>
The structure flag provides information about the relative nonzero pattern of the
Psplit_i matrices, in the same way as in <A HREF="../ST/STSetMatStructure.html#STSetMatStructure">STSetMatStructure</A>().
<P>
Use n=0 to reset a previously set split preconditioner.
<P>
<P>
<H3><FONT COLOR="#883300">See Also</FONT></H3>
<A HREF="../ST/STGetSplitPreconditionerTerm.html#STGetSplitPreconditionerTerm">STGetSplitPreconditionerTerm</A>(), <A HREF="../ST/STGetSplitPreconditionerInfo.html#STGetSplitPreconditionerInfo">STGetSplitPreconditionerInfo</A>(), <A HREF="../ST/STSetPreconditionerMat.html#STSetPreconditionerMat">STSetPreconditionerMat</A>(), <A HREF="../ST/STSetMatrices.html#STSetMatrices">STSetMatrices</A>(), <A HREF="../ST/STSetMatStructure.html#STSetMatStructure">STSetMatStructure</A>()
<BR><P><B></B><H3><FONT COLOR="#883300">Level</FONT></H3>advanced<BR>
<H3><FONT COLOR="#883300">Location</FONT></H3>
</B><A HREF="../../../src/sys/classes/st/interface/stfunc.c.html#STSetSplitPreconditioner">src/sys/classes/st/interface/stfunc.c</A>
<P><H3><FONT COLOR="#883300">Examples</FONT></H3>
<A HREF="../../../src/eps/tutorials/ex49.c.html">src/eps/tutorials/ex49.c</A><BR>
<A HREF="../../../src/pep/tutorials/ex50.c.html">src/pep/tutorials/ex50.c</A><BR>
<BR><BR><A HREF="./index.html">Index of all ST routines</A>
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