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<div id="version" align=right><b>slepc-3.23.1 2025-05-01</b></div>
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<H1>BVTensorCompress</H1>
Updates the U and S factors of the tensor basis vectors object V by means of an <A HREF="../SVD/SVD.html#SVD">SVD</A>, removing redundant information.
<H3><FONT COLOR="#883300">Synopsis</FONT></H3>
<PRE>
#include "slepcbv.h"
<A HREF="https://petsc.org/release/manualpages/Sys/PetscErrorCode.html#PetscErrorCode">PetscErrorCode</A> <A HREF="../BV/BVTensorCompress.html#BVTensorCompress">BVTensorCompress</A>(<A HREF="../BV/BV.html#BV">BV</A> V,<A HREF="https://petsc.org/release/manualpages/Sys/PetscInt.html#PetscInt">PetscInt</A> newc)
</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>V </B></TD><TD> - the tensor basis vectors context
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>newc </B></TD><TD> - additional columns to be locked
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#883300">Notes</FONT></H3>
This function is typically used when restarting Krylov solvers. Truncating a
tensor <A HREF="../BV/BV.html#BV">BV</A> V = (I otimes U) S to its leading columns amounts to keeping the
leading columns of S. However, to effectively reduce the size of the
decomposition, it is necessary to compress it in a way that fewer columns of
U are employed. This can be achieved by means of an update that involves the
<A HREF="../SVD/SVD.html#SVD">SVD</A> of the low-rank matrix [S_0 S_1 ... S_{d-1}], where S_i are the pieces of S.
<P>
If newc is nonzero, then newc columns are added to the leading columns of V.
This means that the corresponding columns of the U and S factors will remain
invariant in subsequent operations.
<P>
<P>
<H3><FONT COLOR="#883300">See Also</FONT></H3>
<A HREF="../BV/BVCreateTensor.html#BVCreateTensor">BVCreateTensor</A>(), <A HREF="../BV/BVSetActiveColumns.html#BVSetActiveColumns">BVSetActiveColumns</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/bv/impls/tensor/bvtensor.c.html#BVTensorCompress">src/sys/classes/bv/impls/tensor/bvtensor.c</A>
<BR><BR><A HREF="./index.html">Index of all BV routines</A>
<BR><A HREF="../../../docs/manual.html">Table of Contents for all manual pages</A>
<BR><A HREF="../singleindex.html">Index of all manual pages</A>
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