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<div id="version" align=right><b>petsc-3.4.2 2013-07-02</b></div>
<A NAME="MatMatMultSymbolic"><H1>MatMatMultSymbolic</H1></A>
Performs construction, preallocation, and computes the ij structure of the matrix-matrix product C=A*B. Call this routine before calling <A HREF="../Mat/MatMatMultNumeric.html#MatMatMultNumeric">MatMatMultNumeric</A>().
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
#include "petscmat.h"
PetscErrorCode MatMatMultSymbolic(Mat A,Mat B,PetscReal fill,Mat *C)
</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>A </B></TD><TD>- the left matrix
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>B </B></TD><TD>- the right matrix
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>fill </B></TD><TD>- expected fill as ratio of nnz(C)/(nnz(A) + nnz(B)), use <A HREF="../Sys/PETSC_DEFAULT.html#PETSC_DEFAULT">PETSC_DEFAULT</A> if you do not have a good estimate,
if C is a dense matrix this is irrelevent
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Output Parameters</FONT></H3>
<DT><B>C </B> -the product matrix
<br>
<P>
<H3><FONT COLOR="#CC3333">Notes</FONT></H3>
Unless scall is MAT_REUSE_MATRIX C will be created.
<P>
To determine the correct fill value, run with -info and search for the string "Fill ratio" to see the value
actually needed.
<P>
This routine is currently implemented for
- pairs of AIJ matrices and classes which inherit from AIJ, C will be of type AIJ
- pairs of AIJ (A) and Dense (B) matrix, C will be of type Dense.
- pairs of Dense (A) and AIJ (B) matrix, C will be of type Dense.
<P>
<P>
Developers Note: There are ways to estimate the number of nonzeros in the resulting product, see for example, http://arxiv.org/abs/1006.4173
We should incorporate them into PETSc.
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../Mat/MatMatMult.html#MatMatMult">MatMatMult</A>(), <A HREF="../Mat/MatMatMultNumeric.html#MatMatMultNumeric">MatMatMultNumeric</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#MatMatMultSymbolic">src/mat/interface/matrix.c</A>
<BR><A HREF="./index.html">Index of all Mat routines</A>
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