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				| <!-------- @HEADER
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|  !
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|  ! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
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|  !
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|  !  Zoltan Toolkit for Load-balancing, Partitioning, Ordering and Coloring
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|  !                  Copyright 2012 Sandia Corporation
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|  ! the U.S. Government retains certain rights in this software.
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|  ! Questions? Contact Karen Devine	kddevin@sandia.gov
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|  !                    Erik Boman	egboman@sandia.gov
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|  !
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|  ! @HEADER
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| -------> 
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| 
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| <!doctype html public "-//w3c//dtd html 4.0 transitional//en">
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| <html>
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| <head>
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|    <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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|    <meta name="GENERATOR" content="Mozilla/4.7 [en] (X11; U; SunOS 5.7 sun4u) [Netscape]">
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|   <meta name="sandia.approval_type" content="formal">
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|   <meta name="sandia.approved" content="SAND2007-4748W">
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|   <meta name="author" content="Zoltan PI">
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| 
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|    <title>Zoltan User's Guide:  RIB</title>
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| </head>
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| <body bgcolor="#FFFFFF">
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| 
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| <div ALIGN=right><b><i><a href="ug.html">Zoltan User's Guide</a>  |  <a href="ug_alg_hsfc.html">Next</a>  |  <a href="ug_alg_rcb.html">Previous</a></i></b></div>
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| 
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| 
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| <h2>
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| <a NAME="RIB"></a>Recursive Inertial Bisection (RIB)</h2>
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| An implementation of Recursive Inertial Bisection (RIB) is included in
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| Zoltan. RIB was proposed as a load-balancing algorithm by 
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| <a href="ug_refs.html#williams">Williams</a> and later studied 
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| by <a href="ug_refs.html#taylor">Taylor and Nour-Omid</a>, but its 
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| origin is unclear.  RIB is similar to RCB in that it divides the domain based on
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| the location of the objects being partitioned by use of cutting planes.
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| In RIB, the computational domain is first divided into two regions by a
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| cutting plane orthogonal to the longest direction of the domain so that half
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| the work load is in each of the sub-regions.  The sub-regions are then further
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| divided by recursive application of the same splitting algorithm until
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| the number of sub-regions equals the number of processors.  Although this
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| algorithm was first devised to cut into a number of sets which is a power
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| of two, the set sizes in a particular cut needn't be equal.  By adjusting
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| the part sizes appropriately, any number of equally-sized sets can
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| be created.  If the parallel machine has processors with different speeds,
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| sets with nonuniform sizes can also be easily generated.  The Zoltan implementation
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| of RIB has several parameters which can be modified by the <b><a href="ug_interface_init.html#Zoltan_Set_Param">Zoltan_Set_Param</a></b>
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| function.
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| <p>
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| RIB currently does not support multiple vertex weights. For such cases, use RCB instead.
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| </p>
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| <br> 
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| <table WIDTH="100%" NOSAVE >
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| <tr>
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| <td VALIGN=TOP WIDTH="20%"><b>Method String:</b></td>
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| 
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| <td><b>RIB</b></td>
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| </tr>
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| 
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| <tr>
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| <td><b>Parameters:</b></td>
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| 
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| <td></td>
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| </tr>
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| 
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| <tr>
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| <td VALIGN=TOP>    <i>RIB_OVERALLOC</i></td>
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| 
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| <td>The amount by which to over-allocate temporary storage arrays for objects
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| within the RIB algorithm when additional storage is due to changes in processor
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| assignments. 
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| <br>1.0 = no extra storage allocated; 1.5 = 50% extra storage; etc.</td>
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| </tr>
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| 
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| <tr>
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| <td VALIGN=TOP NOSAVE>  <i> RIB_OUTPUT_LEVEL</i></td>
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| 
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| <td>Flag controlling the amount of timing and diagnostic output the routine
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| produces. 
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| <br>0 = no output; 1 = print summary; 2 = print data for each processor.</td>
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| </tr>
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| 
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| <tr>
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| <td VALIGN=TOP NOSAVE>  <i> CHECK_GEOM</i></td>
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| 
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| <td>Flag controlling the invocation of input and output error checking. 
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| <br>0 = don't do checking; 1 = do checking.</td>
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| </tr>
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| 
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| <tr>
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| <td VALIGN=TOP NOSAVE>  <i> KEEP_CUTS</i></td>
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| 
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| <td>Should information about the cuts determining the RIB decomposition
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| be retained? It costs a bit of time to do so, but this information is necessary
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| if application wants to add more objects to the decomposition via calls
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| to <b><a href="ug_interface_augment.html#Zoltan_LB_Point_PP_Assign">Zoltan_LB_Point_PP_Assign</a></b>
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| or to <b><a href="ug_interface_augment.html#Zoltan_LB_Box_PP_Assign">Zoltan_LB_Box_PP_Assign</a></b>. 
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| <br>0 = don't keep cuts; 1 = keep cuts.</td>
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| </tr>
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| 
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| <tr>
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| <td VALIGN=TOP NOSAVE>  <i> AVERAGE_CUTS</i></td>
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| 
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| <td>When set to one, coordinates of RIB cutting planes are computed to be the
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| average of the coordinates of the closest object on each side of the cut.
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| Otherwise, coordinates of cutting planes may equal those of one of the
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| closest objects.
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| <br>0 = don't average cuts; 1 = average cuts.</td>
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| </tr>
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| 
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| <tr>
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| <td VALIGN=TOP NOSAVE>  <i> REDUCE_DIMENSIONS</i></td>
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| <td>
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| When a 3 dimensional geometry is almost flat, it may make more
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| sense to treat it as a 2 dimensional geometry when applying the RIB
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| algorithm.  (Coordinate values in the omitted direction are ignored
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| for the purposes of partitioning.)
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| If this parameter is set to <B>1</B>, a 3 dimensional
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| geometry will be treated as 2 dimensional if it is very flat,
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| or 1 dimensional if it is very thin.  A 2 dimensional geometry will
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| be treated as 1 dimensional if it is very thin.
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| </td>
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| </tr>
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| <tr>
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| <td VALIGN=TOP NOSAVE>  <i> DEGENERATE_RATIO</i></td>
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| <td>
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| If the <B>REDUCE_DIMENSIONS</B> parameter is set, then this parameter
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| determines when a geometry is considered to be degenerate.
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| A bounding box which is oriented to the geometry is constructed, and
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| the lengths of its sides are tested against a ratio of 1 : <B>DEGENERATE_RATIO</B>.
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| </td>
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| </tr>
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| 
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| 
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| <tr>
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| <td VALIGN=TOP><b>Default:</b></td>
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| 
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| <td></td>
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| </tr>
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| 
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| <tr>
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| <td></td>
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| 
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| <td><i>RIB_OVERALLOC</i> = 1.2</td>
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| </tr>
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| 
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| <tr>
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| <td></td>
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| 
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| <td><i>RIB_OUTPUT_LEVEL</i> = 0</td>
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| </tr>
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| 
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| <tr>
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| <td></td>
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| 
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| <td><i>CHECK_GEOM</i> = 1</td>
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| </tr>
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| 
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| <tr>
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| <td></td>
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| 
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| <td><i>KEEP_CUTS</i> = 0</td>
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| </tr>
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| 
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| <tr>
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| <td></td>
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| 
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| <td><i>AVERAGE_CUTS</i> = 0</td>
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| </tr>
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| 
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| <tr>
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| <td></td>
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| 
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| <td><i>REDUCE_DIMENSIONS</i> = 0</td>
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| </tr>
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| 
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| <tr>
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| <td></td>
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| 
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| <td><i>DEGENERATE_RATIO</i> = 10</td>
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| </tr>
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| 
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| <tr>
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| <td VALIGN=TOP><b>Required Query Functions:</b></td>
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| 
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| <td></td>
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| </tr>
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| 
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| <tr>
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| <td></td>
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| 
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| <td><b><a href="ug_query_lb.html#ZOLTAN_NUM_OBJ_FN">ZOLTAN_NUM_OBJ_FN</a></b></td>
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| </tr>
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| 
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| <tr>
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| <td></td>
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| 
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| <td><b><a href="ug_query_lb.html#ZOLTAN_OBJ_LIST_FN">ZOLTAN_OBJ_LIST_FN</a></b>
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| </td>
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| </tr>
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| 
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| <tr>
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| <td></td>
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| 
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| <td><b><a href="ug_query_lb.html#ZOLTAN_NUM_GEOM_FN">ZOLTAN_NUM_GEOM_FN</a></b></td>
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| </tr>
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| 
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| <tr>
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| <td></td>
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| 
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| <td>
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| <b><a href="ug_query_lb.html#ZOLTAN_GEOM_MULTI_FN">ZOLTAN_GEOM_MULTI_FN</a></b>
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| or <b><a href="ug_query_lb.html#ZOLTAN_GEOM_FN">ZOLTAN_GEOM_FN</a></b>
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| </td>
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| 
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| </tr>
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| </table>
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| 
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| <p>
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| <hr WIDTH="100%">[<a href="ug.html">Table of Contents</a>  | 
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| <a href="ug_alg_hsfc.html">Next: 
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| Hilbert Space-Filling Curve Partitioning</a> |  <a href="ug_alg_rcb.html">Previous: 
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| Recursive Coordinate Bisection (RCB)</a>  |  <a href="https://www.sandia.gov/general/privacy-security/index.html">Privacy and Security</a>]
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| </body>
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| </html>
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| 
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