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<div id="version" align=right><b>slepc-3.23.1 2025-05-01</b></div>
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<H1>NEPSetWhichEigenpairs</H1>
Specifies which portion of the spectrum is to be sought.
<H3><FONT COLOR="#883300">Synopsis</FONT></H3>
<PRE>
#include "slepcnep.h"
<A HREF="https://petsc.org/release/manualpages/Sys/PetscErrorCode.html#PetscErrorCode">PetscErrorCode</A> <A HREF="../NEP/NEPSetWhichEigenpairs.html#NEPSetWhichEigenpairs">NEPSetWhichEigenpairs</A>(<A HREF="../NEP/NEP.html#NEP">NEP</A> nep,<A HREF="../NEP/NEPWhich.html#NEPWhich">NEPWhich</A> which)
</PRE>
Logically 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>nep </B></TD><TD> - eigensolver context obtained from <A HREF="../NEP/NEPCreate.html#NEPCreate">NEPCreate</A>()
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>which </B></TD><TD> - the portion of the spectrum to be sought
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#883300">Options Database Keys</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-nep_largest_magnitude </B></TD><TD> - Sets largest eigenvalues in magnitude
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-nep_smallest_magnitude </B></TD><TD> - Sets smallest eigenvalues in magnitude
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-nep_largest_real </B></TD><TD> - Sets largest real parts
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-nep_smallest_real </B></TD><TD> - Sets smallest real parts
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-nep_largest_imaginary </B></TD><TD> - Sets largest imaginary parts
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-nep_smallest_imaginary </B></TD><TD> - Sets smallest imaginary parts
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-nep_target_magnitude </B></TD><TD> - Sets eigenvalues closest to target
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-nep_target_real </B></TD><TD> - Sets real parts closest to target
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-nep_target_imaginary </B></TD><TD> - Sets imaginary parts closest to target
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-nep_all </B></TD><TD> - Sets all eigenvalues in a region
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#883300">Notes</FONT></H3>
The parameter 'which' can have one of these values
<P>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B><A HREF="../NEP/NEPWhich.html#NEPWhich">NEP_LARGEST_MAGNITUDE</A> </B></TD><TD> - largest eigenvalues in magnitude (default)
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B><A HREF="../NEP/NEPWhich.html#NEPWhich">NEP_SMALLEST_MAGNITUDE</A> </B></TD><TD> - smallest eigenvalues in magnitude
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B><A HREF="../NEP/NEPWhich.html#NEPWhich">NEP_LARGEST_REAL</A> </B></TD><TD> - largest real parts
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B><A HREF="../NEP/NEPWhich.html#NEPWhich">NEP_SMALLEST_REAL</A> </B></TD><TD> - smallest real parts
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B><A HREF="../NEP/NEPWhich.html#NEPWhich">NEP_LARGEST_IMAGINARY</A> </B></TD><TD> - largest imaginary parts
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B><A HREF="../NEP/NEPWhich.html#NEPWhich">NEP_SMALLEST_IMAGINARY</A> </B></TD><TD> - smallest imaginary parts
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B><A HREF="../NEP/NEPWhich.html#NEPWhich">NEP_TARGET_MAGNITUDE</A> </B></TD><TD> - eigenvalues closest to the target (in magnitude)
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B><A HREF="../NEP/NEPWhich.html#NEPWhich">NEP_TARGET_REAL</A> </B></TD><TD> - eigenvalues with real part closest to target
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B><A HREF="../NEP/NEPWhich.html#NEPWhich">NEP_TARGET_IMAGINARY</A> </B></TD><TD> - eigenvalues with imaginary part closest to target
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B><A HREF="../NEP/NEPWhich.html#NEPWhich">NEP_ALL</A> </B></TD><TD> - all eigenvalues contained in a given region
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B><A HREF="../NEP/NEPWhich.html#NEPWhich">NEP_WHICH_USER</A> </B></TD><TD> - user defined ordering set with <A HREF="../NEP/NEPSetEigenvalueComparison.html#NEPSetEigenvalueComparison">NEPSetEigenvalueComparison</A>()
</TD></TR></TABLE>
<P>
Not all eigensolvers implemented in <A HREF="../NEP/NEP.html#NEP">NEP</A> account for all the possible values
stated above. If SLEPc is compiled for real numbers <A HREF="../NEP/NEPWhich.html#NEPWhich">NEP_LARGEST_IMAGINARY</A>
and <A HREF="../NEP/NEPWhich.html#NEPWhich">NEP_SMALLEST_IMAGINARY</A> use the absolute value of the imaginary part
for eigenvalue selection.
<P>
The target is a scalar value provided with <A HREF="../NEP/NEPSetTarget.html#NEPSetTarget">NEPSetTarget</A>().
<P>
<A HREF="../NEP/NEPWhich.html#NEPWhich">NEP_ALL</A> is intended for use in the context of the CISS solver for
computing all eigenvalues in a region.
<P>
<P>
<H3><FONT COLOR="#883300">See Also</FONT></H3>
<A HREF="../NEP/NEPGetWhichEigenpairs.html#NEPGetWhichEigenpairs">NEPGetWhichEigenpairs</A>(), <A HREF="../NEP/NEPSetTarget.html#NEPSetTarget">NEPSetTarget</A>(), <A HREF="../NEP/NEPSetEigenvalueComparison.html#NEPSetEigenvalueComparison">NEPSetEigenvalueComparison</A>(), <A HREF="../NEP/NEPWhich.html#NEPWhich">NEPWhich</A>
<BR><P><B></B><H3><FONT COLOR="#883300">Level</FONT></H3>intermediate<BR>
<H3><FONT COLOR="#883300">Location</FONT></H3>
</B><A HREF="../../../src/nep/interface/nepopts.c.html#NEPSetWhichEigenpairs">src/nep/interface/nepopts.c</A>
<BR><BR><A HREF="./index.html">Index of all NEP routines</A>
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