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<div id="version" align=right><b>petsc-3.14.5 2021-03-03</b></div>
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<A NAME="MatPreallocatorPreallocate"><H1>MatPreallocatorPreallocate</H1></A>
Preallocates the A matrix, using information from mat, optionally filling A with zeros
<H3><FONT COLOR="#CC3333">Synopsis</FONT></H3>
<PRE>
#include "petscmat.h"
<A HREF="../Sys/PetscErrorCode.html#PetscErrorCode">PetscErrorCode</A> <A HREF="../Mat/MatPreallocatorPreallocate.html#MatPreallocatorPreallocate">MatPreallocatorPreallocate</A>(<A HREF="../Mat/Mat.html#Mat">Mat</A> mat, <A HREF="../Sys/PetscBool.html#PetscBool">PetscBool</A> fill, <A HREF="../Mat/Mat.html#Mat">Mat</A> A)
</PRE>
<H3><FONT COLOR="#CC3333">Input Parameter</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 preallocator
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>fill </B></TD><TD>- fill the matrix with zeros
</TD></TR>
<TR><TD WIDTH=40></TD><TD ALIGN=LEFT VALIGN=TOP><B>A </B></TD><TD>- the matrix to be preallocated
</TD></TR></TABLE>
<P>
<H3><FONT COLOR="#CC3333">Notes</FONT></H3>
This <A HREF="../Mat/Mat.html#Mat">Mat</A> implementation provides a helper utility to define the correct
preallocation data for a given nonzero structure. Use this object like a
regular matrix, e.g. loop over the nonzero structure of the matrix and
call <A HREF="../Mat/MatSetValues.html#MatSetValues">MatSetValues</A>() or <A HREF="../Mat/MatSetValuesBlocked.html#MatSetValuesBlocked">MatSetValuesBlocked</A>() to indicate the nonzero locations.
The matrix entires provided to <A HREF="../Mat/MatSetValues.html#MatSetValues">MatSetValues</A>() will be ignored, it only uses
the row / col indices provided to determine the information required to be
passed to <A HREF="../Mat/MatXAIJSetPreallocation.html#MatXAIJSetPreallocation">MatXAIJSetPreallocation</A>(). Once you have looped over the nonzero
structure, you must call <A HREF="../Mat/MatAssemblyBegin.html#MatAssemblyBegin">MatAssemblyBegin</A>(), <A HREF="../Mat/MatAssemblyEnd.html#MatAssemblyEnd">MatAssemblyEnd</A>() on mat.
<P>
After you have assembled the preallocator matrix (mat), call <A HREF="../Mat/MatPreallocatorPreallocate.html#MatPreallocatorPreallocate">MatPreallocatorPreallocate</A>()
to define the preallocation information on the matrix (A). Setting the parameter
fill = <A HREF="../Sys/PETSC_TRUE.html#PETSC_TRUE">PETSC_TRUE</A> will insert zeros into the matrix A. Internally <A HREF="../Mat/MatPreallocatorPreallocate.html#MatPreallocatorPreallocate">MatPreallocatorPreallocate</A>()
will call <A HREF="../Mat/MatSetOption.html#MatSetOption">MatSetOption</A>(A, <A HREF="../Mat/MatOption.html#MatOption">MAT_NEW_NONZERO_ALLOCATION_ERR</A>, <A HREF="../Sys/PETSC_TRUE.html#PETSC_TRUE">PETSC_TRUE</A>);
<P>
<P>
<H3><FONT COLOR="#CC3333">See Also</FONT></H3>
<A HREF="../Mat/MATPREALLOCATOR.html#MATPREALLOCATOR">MATPREALLOCATOR</A>
<BR><P><B></B><H3><FONT COLOR="#CC3333">Level</FONT></H3>advanced<BR>
<H3><FONT COLOR="#CC3333">Location</FONT></H3>
</B><A HREF="../../../src/mat/impls/preallocator/matpreallocator.c.html#MatPreallocatorPreallocate">src/mat/impls/preallocator/matpreallocator.c</A>
<P><H3><FONT COLOR="CC3333">Implementations</FONT></H3><A HREF="../../../src/mat/impls/preallocator/matpreallocator.c.html#MatPreallocatorPreallocate_Preallocator">MatPreallocatorPreallocate_Preallocator in src/mat/impls/preallocator/matpreallocator.c</A><BR>
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