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<TITLE>MatSeqSBAIJSetPreallocation</TITLE>
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<A NAME="MatSeqSBAIJSetPreallocation"><H1>MatSeqSBAIJSetPreallocation</H1></A>
Creates a sparse symmetric matrix in block AIJ (block compressed row) format. For good matrix assembly performance the user should preallocate the matrix storage by setting the parameter nz (or the array nnz). By setting these parameters accurately, performance during matrix assembly can be increased by more than a factor of 50.
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
#include "petscmat.h"
int MatSeqSBAIJSetPreallocation(Mat B,int bs,int nz,const int nnz[])</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>A </B></TD><TD>- the symmetric matrix
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>bs </B></TD><TD>- <A HREF="../Sys/size.html#size">size</A> of block
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>nz </B></TD><TD>- number of block nonzeros per block row (same for all rows)
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>nnz </B></TD><TD>- array containing the number of block nonzeros in the upper triangular plus
diagonal portion of each block (possibly different for each block row) or <A HREF="../Sys/PETSC_NULL.html#PETSC_NULL">PETSC_NULL</A>
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Options Database Keys</FONT></H3>
<DT><B>-mat_no_unroll </B> -uses code that does not unroll the loops in the
block calculations (much slower)
<br>
<DT><B>-mat_block_size </B> -<A HREF="../Sys/size.html#size">size</A> of the blocks to use
<br>
<P>
<P>
<H3><FONT COLOR="#CC3333">Notes</FONT></H3>
Specify the preallocated storage with either nz or nnz (not both).
Set nz=<A HREF="../Sys/PETSC_DEFAULT.html#PETSC_DEFAULT">PETSC_DEFAULT</A> and nnz=<A HREF="../Sys/PETSC_NULL.html#PETSC_NULL">PETSC_NULL</A> for PETSc to control dynamic memory
allocation. For additional details, see the users manual chapter on
matrices.
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../Mat/MatCreate.html#MatCreate">MatCreate</A>(), <A HREF="../Mat/MatCreateSeqAIJ.html#MatCreateSeqAIJ">MatCreateSeqAIJ</A>(), <A HREF="../Mat/MatSetValues.html#MatSetValues">MatSetValues</A>(), <A HREF="../Mat/MatCreateMPISBAIJ.html#MatCreateMPISBAIJ">MatCreateMPISBAIJ</A>()
<BR><P><B><P><B><FONT COLOR="#CC3333">Level:</FONT></B>intermediate
<BR><FONT COLOR="#CC3333">Location:</FONT></B><A HREF="../../../src/mat/impls/sbaij/seq/sbaij.c.html#MatSeqSBAIJSetPreallocation">src/mat/impls/sbaij/seq/sbaij.c</A>
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