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<div id="version" align=right><b>slepc-3.23.1 2025-05-01</b></div>
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<H1>DSGetTruncateSize</H1>
Gets the correct size to be used in <A HREF="../DS/DSTruncate.html#DSTruncate">DSTruncate</A>() to avoid breaking a 2x2 block.
<H3><FONT COLOR="#883300">Synopsis</FONT></H3>
<PRE>
#include "slepcds.h"
<A HREF="https://petsc.org/release/manualpages/Sys/PetscErrorCode.html#PetscErrorCode">PetscErrorCode</A> <A HREF="../DS/DSGetTruncateSize.html#DSGetTruncateSize">DSGetTruncateSize</A>(<A HREF="../DS/DS.html#DS">DS</A> ds,<A HREF="https://petsc.org/release/manualpages/Sys/PetscInt.html#PetscInt">PetscInt</A> l,<A HREF="https://petsc.org/release/manualpages/Sys/PetscInt.html#PetscInt">PetscInt</A> n,<A HREF="https://petsc.org/release/manualpages/Sys/PetscInt.html#PetscInt">PetscInt</A> *k)
</PRE>
Not 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>ds </B></TD><TD> - the direct solver context
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>l </B></TD><TD> - the size of the locked part (set to 0 to use ds->l)
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>n </B></TD><TD> - the total matrix size (set to 0 to use ds->n)
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#883300">Output Parameter</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>k </B></TD><TD> - the wanted truncation size (possibly modified)
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#883300">Notes</FONT></H3>
This should be called before <A HREF="../DS/DSTruncate.html#DSTruncate">DSTruncate</A>() to make sure that the truncation
does not break a 2x2 block corresponding to a complex conjugate eigenvalue.
<P>
The total size is n (either user-provided or ds->n if 0 is passed). The
size where the truncation is intended is equal to l+k (where l can be
equal to the locked size ds->l if set to 0). Then if there is a 2x2 block
at the l+k limit, the value of k is increased (or decreased) by 1.
<P>
<P>
<H3><FONT COLOR="#883300">See Also</FONT></H3>
<A HREF="../DS/DSTruncate.html#DSTruncate">DSTruncate</A>(), <A HREF="../DS/DSSetDimensions.html#DSSetDimensions">DSSetDimensions</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/ds/interface/dsops.c.html#DSGetTruncateSize">src/sys/classes/ds/interface/dsops.c</A>
<BR><BR><A HREF="./index.html">Index of all DS routines</A>
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