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<TITLE>SlepcSC</TITLE>
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<div id="version" align=right><b>slepc-3.22.2 2024-12-02</b></div>
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<H1>SlepcSC</H1>
Data structure (C struct) for storing information about the sorting criterion used by different eigensolver objects.
<H3><FONT COLOR="#883300">Synopsis</FONT></H3>
<PRE>
struct _n_SlepcSC {
/* map values before sorting, typically a call to <A HREF="../ST/STBackTransform.html#STBackTransform">STBackTransform</A> (mapctx=<A HREF="../ST/ST.html#ST">ST</A>) */
<A HREF="https://petsc.org/release/manualpages/Sys/PetscErrorCode.html#PetscErrorCode">PetscErrorCode</A> (*map)(<A HREF="https://petsc.org/release/manualpages/Sys/PetscObject.html#PetscObject">PetscObject</A>,<A HREF="https://petsc.org/release/manualpages/Sys/PetscInt.html#PetscInt">PetscInt</A>,<A HREF="https://petsc.org/release/manualpages/Sys/PetscScalar.html#PetscScalar">PetscScalar</A>*,<A HREF="https://petsc.org/release/manualpages/Sys/PetscScalar.html#PetscScalar">PetscScalar</A>*);
<A HREF="https://petsc.org/release/manualpages/Sys/PetscObject.html#PetscObject">PetscObject</A> mapobj;
/* comparison function such as SlepcCompareLargestMagnitude */
<A HREF="../sys/SlepcEigenvalueComparisonFn.html#SlepcEigenvalueComparisonFn">SlepcEigenvalueComparisonFn</A> *comparison;
void *comparisonctx;
/* optional region for filtering */
<A HREF="../RG/RG.html#RG">RG</A> rg;
};
</PRE>
<H3><FONT COLOR="#883300">Notes</FONT></H3>
The <A HREF="../sys/SlepcSC.html#SlepcSC">SlepcSC</A> structure contains a mapping function and a comparison
function (with associated contexts).
The mapping function usually calls <A HREF="../ST/ST.html#ST">ST</A>'s backtransform.
An optional region can also be used to give higher priority to values inside it.
<P>
The comparison function must have the following calling sequence
<P>
<pre>
comparison(<A HREF="https://petsc.org/release/manualpages/Sys/PetscScalar.html#PetscScalar">PetscScalar</A> ar,<A HREF="https://petsc.org/release/manualpages/Sys/PetscScalar.html#PetscScalar">PetscScalar</A> ai,<A HREF="https://petsc.org/release/manualpages/Sys/PetscScalar.html#PetscScalar">PetscScalar</A> br,<A HREF="https://petsc.org/release/manualpages/Sys/PetscScalar.html#PetscScalar">PetscScalar</A> bi,<A HREF="https://petsc.org/release/manualpages/Sys/PetscInt.html#PetscInt">PetscInt</A> *res,void *ctx)
</pre>
<P>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>ar </B></TD><TD> - real part of the 1st eigenvalue
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>ai </B></TD><TD> - imaginary part of the 1st eigenvalue
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>br </B></TD><TD> - real part of the 2nd eigenvalue
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>bi </B></TD><TD> - imaginary part of the 2nd eigenvalue
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>res </B></TD><TD> - result of comparison
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>ctx </B></TD><TD> - optional context, stored in comparisonctx
</TD></TR></TABLE>
<P>
The returning parameter 'res' can be
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>negative </B></TD><TD> - if the 1st value is preferred to the 2st one
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>zero </B></TD><TD> - if both values are equally preferred
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>positive </B></TD><TD> - if the 2st value is preferred to the 1st one
</TD></TR></TABLE>
<P>
Fortran usage is not supported.
<P>
<P>
<H3><FONT COLOR="#883300">See Also</FONT></H3>
<A HREF="../sys/SlepcSCCompare.html#SlepcSCCompare">SlepcSCCompare</A>()
<BR><P><B></B><H3><FONT COLOR="#883300">Level</FONT></H3>developer<BR>
<H3><FONT COLOR="#883300">Location</FONT></H3>
</B><A HREF="../../../include/slepcsc.h.html#SlepcSC">include/slepcsc.h</A>
<BR><BR><A HREF="./index.html">Index of all sys routines</A>
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