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<div id="version" align=right><b>slepc-3.23.1 2025-05-01</b></div>
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<H1>EPSSetInterval</H1>
Defines the computational interval for spectrum slicing.
<H3><FONT COLOR="#883300">Synopsis</FONT></H3>
<PRE>
#include "slepceps.h"
<A HREF="https://petsc.org/release/manualpages/Sys/PetscErrorCode.html#PetscErrorCode">PetscErrorCode</A> <A HREF="../EPS/EPSSetInterval.html#EPSSetInterval">EPSSetInterval</A>(<A HREF="../EPS/EPS.html#EPS">EPS</A> eps,<A HREF="https://petsc.org/release/manualpages/Sys/PetscReal.html#PetscReal">PetscReal</A> inta,<A HREF="https://petsc.org/release/manualpages/Sys/PetscReal.html#PetscReal">PetscReal</A> intb)
</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>eps </B></TD><TD> - eigensolver context
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>inta </B></TD><TD> - left end of the interval
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>intb </B></TD><TD> - right end of the interval
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#883300">Options Database Key</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>-eps_interval <a,b> </B></TD><TD> - set [a,b] as the interval of interest
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#883300">Notes</FONT></H3>
Spectrum slicing is a technique employed for computing all eigenvalues of
symmetric eigenproblems in a given interval. This function provides the
interval to be considered. It must be used in combination with <A HREF="../EPS/EPSWhich.html#EPSWhich">EPS_ALL</A>, see
<A HREF="../EPS/EPSSetWhichEigenpairs.html#EPSSetWhichEigenpairs">EPSSetWhichEigenpairs</A>().
<P>
In the command-line option, two values must be provided. For an open interval,
one can give an infinite, e.g., -eps_interval 1.0,inf or -eps_interval -inf,1.0.
An open interval in the programmatic interface can be specified with
<A HREF="https://petsc.org/release/manualpages/Sys/PETSC_MAX_REAL.html#PETSC_MAX_REAL">PETSC_MAX_REAL</A> and -<A HREF="https://petsc.org/release/manualpages/Sys/PETSC_MAX_REAL.html#PETSC_MAX_REAL">PETSC_MAX_REAL</A>.
<P>
<P>
<H3><FONT COLOR="#883300">See Also</FONT></H3>
<A HREF="../EPS/EPSGetInterval.html#EPSGetInterval">EPSGetInterval</A>(), <A HREF="../EPS/EPSSetWhichEigenpairs.html#EPSSetWhichEigenpairs">EPSSetWhichEigenpairs</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/eps/interface/epsbasic.c.html#EPSSetInterval">src/eps/interface/epsbasic.c</A>
<P><H3><FONT COLOR="#883300">Examples</FONT></H3>
<A HREF="../../../src/eps/tutorials/ex12.c.html">src/eps/tutorials/ex12.c</A><BR>
<A HREF="../../../src/eps/tutorials/ex25.c.html">src/eps/tutorials/ex25.c</A><BR>
<BR><BR><A HREF="./index.html">Index of all EPS routines</A>
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