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<div id="version" align=right><b>petsc-3.7.5 2017-01-01</b></div>
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<A NAME="MatZeroRowsStencil"><H1>MatZeroRowsStencil</H1></A>
Zeros all entries (except possibly the main diagonal) of a set of rows of a matrix. These rows must be local to the process.
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
#include "petscmat.h"
PetscErrorCode MatZeroRowsStencil(Mat mat,PetscInt numRows,const MatStencil rows[],PetscScalar diag,Vec x,Vec b)
</PRE>
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>mat </B></TD><TD>- the matrix
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>numRows </B></TD><TD>- the number of rows to remove
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>rows </B></TD><TD>- the grid coordinates (and component number when dof > 1) for matrix rows
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>diag </B></TD><TD>- value put in all diagonals of eliminated rows (0.0 will even eliminate diagonal entry)
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>x </B></TD><TD>- optional vector of solutions for zeroed rows (other entries in vector are not used)
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>b </B></TD><TD>- optional vector of right hand side, that will be adjusted by provided solution
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Notes</FONT></H3>
For the AIJ and BAIJ matrix formats this removes the old nonzero structure,
but does not release memory. For the dense and block diagonal
formats this does not alter the nonzero structure.
<P>
If the option <A HREF="../Mat/MatSetOption.html#MatSetOption">MatSetOption</A>(mat,MAT_KEEP_NONZERO_PATTERN,<A HREF="../Sys/PETSC_TRUE.html#PETSC_TRUE">PETSC_TRUE</A>) the nonzero structure
of the matrix is not changed (even for AIJ and BAIJ matrices) the values are
merely zeroed.
<P>
The user can set a value in the diagonal entry (or for the AIJ and
row formats can optionally remove the main diagonal entry from the
nonzero structure as well, by passing 0.0 as the final argument).
<P>
For the parallel case, all processes that share the matrix (i.e.,
those in the communicator used for matrix creation) MUST call this
routine, regardless of whether any rows being zeroed are owned by
them.
<P>
Each processor can indicate any rows in the entire matrix to be zeroed (i.e. each process does NOT have to
list only rows local to itself).
<P>
The grid coordinates are across the entire grid, not just the local portion
<P>
In Fortran idxm and idxn should be declared as
<pre>
<A HREF="../Mat/MatStencil.html#MatStencil">MatStencil</A> idxm(4,m)
</pre>
and the values inserted using
<pre>
idxm(MatStencil_i,1) = i
</pre>
<pre>
idxm(MatStencil_j,1) = j
</pre>
<pre>
idxm(MatStencil_k,1) = k
</pre>
<pre>
idxm(MatStencil_c,1) = c
</pre>
etc
<P>
For periodic boundary conditions use negative indices for values to the left (below 0; that are to be
obtained by wrapping values from right edge). For values to the right of the last entry using that index plus one
etc to obtain values that obtained by wrapping the values from the left edge. This does not work for anything but the
DM_BOUNDARY_PERIODIC boundary type.
<P>
For indices that don't mean anything for your case (like the k index when working in 2d) or the c index when you have
a single value per point) you can skip filling those indices.
<P>
<P>
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../Mat/MatZeroRows.html#MatZeroRows">MatZeroRows</A>(), <A HREF="../Mat/MatZeroRowsIS.html#MatZeroRowsIS">MatZeroRowsIS</A>(), <A HREF="../Mat/MatZeroEntries.html#MatZeroEntries">MatZeroEntries</A>(), <A HREF="../Mat/MatZeroRowsLocal.html#MatZeroRowsLocal">MatZeroRowsLocal</A>(), <A HREF="../Mat/MatSetOption.html#MatSetOption">MatSetOption</A>()
<BR><P><B><P><B><FONT COLOR="#CC3333">Level:</FONT></B>intermediate
<BR><FONT COLOR="#CC3333">Location:</FONT></B><A HREF="../../../src/mat/interface/matrix.c.html#MatZeroRowsStencil">src/mat/interface/matrix.c</A>
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