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<TITLE>MatShift</TITLE>
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<div id="version" align=right><b>petsc-3.10.3 2018-12-18</b></div>
<div id="bugreport" align=right><a href="mailto:petsc-maint@mcs.anl.gov?subject=Typo or Error in Documentation &body=Please describe the typo or error in the documentation: petsc-3.10.3 v3.10.3 docs/manualpages/Mat/MatShift.html "><small>Report Typos and Errors</small></a></div>
<A NAME="MatShift"><H1>MatShift</H1></A>
Computes Y = Y + a I, where a is a <A HREF="../Sys/PetscScalar.html#PetscScalar">PetscScalar</A> and I is the identity matrix.
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
#include "petscmat.h"
<A HREF="../Sys/PetscErrorCode.html#PetscErrorCode">PetscErrorCode</A> <A HREF="../Mat/MatShift.html#MatShift">MatShift</A>(<A HREF="../Mat/Mat.html#Mat">Mat</A> Y,<A HREF="../Sys/PetscScalar.html#PetscScalar">PetscScalar</A> a)
</PRE>
Neighbor-wise Collective on <A HREF="../Mat/Mat.html#Mat">Mat</A>
<P>
<H3><FONT COLOR="#CC3333">Input Parameters</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>Y </B></TD><TD>- the matrices
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>a </B></TD><TD>- the <A HREF="../Sys/PetscScalar.html#PetscScalar">PetscScalar</A>
</TD></TR></TABLE>
<P>
<P>
<H3><FONT COLOR="#CC3333">Notes</FONT></H3>
If the matrix Y is missing some diagonal entries this routine can be very slow. To make it fast one should initially
fill the matrix so that all diagonal entries have a value (with a value of zero for those locations that would not have an
entry).
<P>
To form Y = Y + diag(V) use <A HREF="../Mat/MatDiagonalSet.html#MatDiagonalSet">MatDiagonalSet</A>()
<P>
Developers Note: If the local "diagonal part" of the matrix Y has no entries then the local diagonal part is
preallocated with 1 nonzero per row for the to be added values. This allows for fast shifting of an empty matrix.
<P>
<H3><FONT COLOR="#CC3333">Keywords</FONT></H3>
matrix, add, shift
<BR>
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../Mat/MatDiagonalSet.html#MatDiagonalSet">MatDiagonalSet</A>(), <A HREF="../Mat/MatScale.html#MatScale">MatScale</A>(), <A HREF="../Mat/MatDiagonalScale.html#MatDiagonalScale">MatDiagonalScale</A>()
<BR><P><B></B><H3><FONT COLOR="#CC3333">Level</FONT></H3>intermediate<BR>
<H3><FONT COLOR="#CC3333">Location</FONT></H3>
</B><A HREF="../../../src/mat/utils/axpy.c.html#MatShift">src/mat/utils/axpy.c</A>
<P><H3><FONT COLOR="#CC3333">Examples</FONT></H3>
<A HREF="../../../src/mat/examples/tutorials/ex9.c.html">src/mat/examples/tutorials/ex9.c.html</A><BR>
<A HREF="../../../src/ts/examples/tutorials/ex3.c.html">src/ts/examples/tutorials/ex3.c.html</A><BR>
<A HREF="../../../src/tao/pde_constrained/examples/tutorials/parabolic.c.html">src/tao/pde_constrained/examples/tutorials/parabolic.c.html</A><BR>
<A HREF="../../../src/tao/pde_constrained/examples/tutorials/hyperbolic.c.html">src/tao/pde_constrained/examples/tutorials/hyperbolic.c.html</A><BR>
<P><H3><FONT COLOR="CC3333">Implementations</FONT></H3><A HREF="../../../src/mat/impls/aij/mpi/mpiaij.c.html#MatShift_MPIAIJ">MatShift_MPIAIJ in src/mat/impls/aij/mpi/mpiaij.c</A><BR>
<A HREF="../../../src/mat/impls/aij/seq/aij.c.html#MatShift_SeqAIJ">MatShift_SeqAIJ in src/mat/impls/aij/seq/aij.c</A><BR>
<A HREF="../../../src/mat/impls/baij/mpi/mpibaij.c.html#MatShift_MPIBAIJ">MatShift_MPIBAIJ in src/mat/impls/baij/mpi/mpibaij.c</A><BR>
<A HREF="../../../src/mat/impls/baij/seq/baij.c.html#MatShift_SeqBAIJ">MatShift_SeqBAIJ in src/mat/impls/baij/seq/baij.c</A><BR>
<A HREF="../../../src/mat/impls/is/matis.c.html#MatShift_IS">MatShift_IS in src/mat/impls/is/matis.c</A><BR>
<A HREF="../../../src/mat/impls/mffd/mffd.c.html#MatShift_MFFD">MatShift_MFFD in src/mat/impls/mffd/mffd.c</A><BR>
<A HREF="../../../src/mat/impls/nest/matnest.c.html#MatShift_Nest">MatShift_Nest in src/mat/impls/nest/matnest.c</A><BR>
<A HREF="../../../src/mat/impls/sbaij/mpi/mpisbaij.c.html#MatShift_MPISBAIJ">MatShift_MPISBAIJ in src/mat/impls/sbaij/mpi/mpisbaij.c</A><BR>
<A HREF="../../../src/mat/impls/sbaij/seq/sbaij.c.html#MatShift_SeqSBAIJ">MatShift_SeqSBAIJ in src/mat/impls/sbaij/seq/sbaij.c</A><BR>
<A HREF="../../../src/mat/impls/sell/mpi/mpisell.c.html#MatShift_MPISELL">MatShift_MPISELL in src/mat/impls/sell/mpi/mpisell.c</A><BR>
<A HREF="../../../src/mat/impls/sell/seq/sell.c.html#MatShift_SeqSELL">MatShift_SeqSELL in src/mat/impls/sell/seq/sell.c</A><BR>
<A HREF="../../../src/mat/impls/shell/shell.c.html#MatShift_Shell">MatShift_Shell in src/mat/impls/shell/shell.c</A><BR>
<A HREF="../../../src/mat/impls/submat/submat.c.html#MatShift_SubMatrix">MatShift_SubMatrix in src/mat/impls/submat/submat.c</A><BR>
<BR><A HREF="./index.html">Index of all Mat routines</A>
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