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<div id="version" align=right><b>petsc-3.4.2 2013-07-02</b></div>
<A NAME="MatPreallocateInitialize"><H1>MatPreallocateInitialize</H1></A>
Begins the block of code that will count the number of nonzeros per row in a matrix providing the data that one can use to correctly preallocate the matrix.
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
#include "petscmat.h"
PetscErrorCode MatPreallocateInitialize(MPI_Comm comm, PetscInt nrows, PetscInt ncols, PetscInt *dnz, PetscInt *onz)
</PRE>
Collective on <A HREF="../Sys/MPI_Comm.html#MPI_Comm">MPI_Comm</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>comm </B></TD><TD>- the communicator that will share the eventually allocated matrix
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>nrows </B></TD><TD>- the number of LOCAL rows in the matrix
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>ncols </B></TD><TD>- the number of LOCAL columns in the matrix
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Output Parameters</FONT></H3>
<TABLE border="0" cellpadding="0" cellspacing="0">
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>dnz </B></TD><TD>- the array that will be passed to the matrix preallocation routines
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>ozn </B></TD><TD>- the other array passed to the matrix preallocation routines
</TD></TR></TABLE>
<P>
<P>
<P>
<H3><FONT COLOR="#CC3333">Notes</FONT></H3>
See the <A href="../../docs/manual.pdf#nameddest=<A HREF="../../manual.pdf#chapter.11">Chapter 11 Hints for Performance Tuning</A>">Hints for Performance Improvment</A> chapter in the users manual for more details.
<P>
Do not malloc or free dnz and onz, that is handled internally by these routines
<P>
Use MatPreallocateInitializeSymmetric() for symmetric matrices (MPISBAIJ matrices)
<P>
This is a MACRO not a function because it has a leading { that is closed by PetscPreallocateFinalize().
<P>
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../Mat/MatPreallocateFinalize.html#MatPreallocateFinalize">MatPreallocateFinalize</A>(), <A HREF="../Mat/MatPreallocateSet.html#MatPreallocateSet">MatPreallocateSet</A>(), <A HREF="../Mat/MatPreallocateSymmetricSet.html#MatPreallocateSymmetricSet">MatPreallocateSymmetricSet</A>(), <A HREF="../Mat/MatPreallocateSetLocal.html#MatPreallocateSetLocal">MatPreallocateSetLocal</A>(),
<BR>MatPreallocateInitializeSymmetric(), <A HREF="../Mat/MatPreallocateSymmetricSetLocal.html#MatPreallocateSymmetricSetLocal">MatPreallocateSymmetricSetLocal</A>()
<P><B><P><B><FONT COLOR="#CC3333">Level:</FONT></B>intermediate
<BR><FONT COLOR="#CC3333">Location:</FONT></B><A HREF="../../../src/mat/../../include/petscmat.h.html#MatPreallocateInitialize">src/mat/../../include/petscmat.h</A>
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