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173 lines
8.9 KiB
173 lines
8.9 KiB
<!-------- @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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! Under the terms of Contract DE-AC04-94AL85000 with Sandia Corporation,
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! the U.S. Government retains certain rights in this software.
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! Redistribution and use in source and binary forms, with or without
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! modification, are permitted provided that the following conditions are
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! met:
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!
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! 1. Redistributions of source code must retain the above copyright
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! notice, this list of conditions and the following disclaimer.
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! 2. Redistributions in binary form must reproduce the above copyright
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! notice, this list of conditions and the following disclaimer in the
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! documentation and/or other materials provided with the distribution.
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! 3. Neither the name of the Corporation nor the names of the
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! contributors may be used to endorse or promote products derived from
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! this software without specific prior written permission.
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! THIS SOFTWARE IS PROVIDED BY SANDIA CORPORATION "AS IS" AND ANY
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! EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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! IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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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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<!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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<title>Zoltan User's Guide: Load-Balancing Examples</title>
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</head>
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<body bgcolor="#FFFFFF">
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<div align=right><b><i><a href="ug.html">Zoltan User's Guide</a>
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| <a href="ug_examples_mig.html">Next</a> | <a href="ug_examples_init.html">Previous</a></i></b></div>
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<h2>
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<a NAME="Load-Balancing Example"></a>Load-Balancing Example</h2>
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An example of the typical calling sequence for load balancing using Zoltan
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in a finite element application is shown in the <a href="#LB Example Fig">figure</a>
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below. An application first selects a load-balancing algorithm
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by setting the <a href="ug_alg.html#LB_METHOD"><i>LB_METHOD</i></a> parameter
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with
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<b><a href="ug_interface_init.html#Zoltan_Set_Param">Zoltan_Set_Param</a></b>.
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Next, other parameter values are set by calls to
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<b><a href="ug_interface_init.html#Zoltan_Set_Param">Zoltan_Set_Param</a></b>.
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After some computation, load balancing is invoked by calling <b><a href="ug_interface_lb.html#Zoltan_LB_Partition">Zoltan_LB_Partition</a></b>.
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The results of the load balancing include the number of nodes to be imported
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and exported to the processor, lists of global and local IDs of the imported
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and exported nodes, and source and destination processors of the imported
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and exported nodes. A returned argument of <b><a href="ug_interface_lb.html#Zoltan_LB_Partition">Zoltan_LB_Partition</a></b>
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is tested to see whether the new decomposition differs from the old one.
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If the decompositions differ, some sort of data migration is needed to
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establish the new decomposition; the details of migration are not shown
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in this <a href="#LB Example Fig">figure</a> but will be addressed in the
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<a href="ug_examples_mig.html">migration
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examples</a>. After the data migration is completed, the arrays of information
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about imported and exported nodes returned by <b><a href="ug_interface_lb.html#Zoltan_LB_Partition">Zoltan_LB_Partition</a></b>
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are freed by a call to <b><a href="ug_interface_lb.html#Zoltan_LB_Free_Part">Zoltan_LB_Free_Part</a></b>.
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<br>
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<br>
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<center><table BORDER=2 COLS=1 WIDTH="90%" NOSAVE >
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<tr>
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<td><a NAME="LB Example Fig"></a><tt>char *lb_method;</tt>
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<br><tt>int new, num_imp, num_exp, *imp_procs, *exp_procs;</tt>
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<br><tt>int *imp_to_part, *exp_to_part;</tt>
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<br><tt>int num_gid_entries, num_lid_entries;</tt>
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<br><tt><a href="ug_usage.html#Data Types for Object IDs">ZOLTAN_ID_PTR</a> imp_global_ids,
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exp_global_ids;</tt>
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<br><tt><a href="ug_usage.html#Data Types for Object IDs">ZOLTAN_ID_PTR</a>
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imp_local_ids, exp_local_ids;</tt>
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<p><tt>/* <i>Set load-balancing method.</i> */</tt>
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<br><tt>read_load_balancing_info_from_input_file(&lb_method);</tt>
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<br><tt><a href="ug_interface_init.html#Zoltan_Set_Param">Zoltan_Set_Param</a>(zz,
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"LB_METHOD", lb_method);</tt>
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<p><tt>/* <i>Reset some load-balancing parameters.</i> */</tt>
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<br><tt><a href="ug_interface_init.html#Zoltan_Set_Param">Zoltan_Set_Param</a>(zz,
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"RCB_Reuse", "TRUE");</tt>
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<p><tt>/* <i>Perform computations</i> */</tt>
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<br><tt>...</tt>
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<br><tt>/* <i>Perform load balancing</i> */</tt>
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<br><tt><a href="ug_interface_lb.html#Zoltan_LB_Partition">Zoltan_LB_Partition</a>(zz,&new,&num_gid_entries,&num_lid_entries,</tt>
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<br><tt> &num_imp,&imp_global_ids,&imp_local_ids,&imp_procs,&imp_to_part,</tt>
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<br><tt> &num_exp,&exp_global_ids,&exp_local_ids,&exp_procs,&exp_to_part); </tt>
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<br><tt>if (new)</tt>
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<br><tt> perform_data_migration(...);</tt>
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<p><tt>/* <i>Free memory allocated for load-balancing results by Zoltan library</i>
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*/</tt>
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<br><tt><a href="ug_interface_lb.html#Zoltan_LB_Free_Part">Zoltan_LB_Free_Part</a>(&imp_global_ids,
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&imp_local_ids, &imp_procs, &imp_to_part);</tt>
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<br><tt><a href="ug_interface_lb.html#Zoltan_LB_Free_Part">Zoltan_LB_Free_Part</a>(&exp_global_ids,
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&exp_local_ids, &exp_procs, &exp_to_part);</tt>
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<br><tt>...</tt>
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</td>
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</tr>
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<caption ALIGN=BOTTOM><i>Typical calling sequence for performing load balancing
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with the Zoltan library.</i></caption>
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</table></center>
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<br>
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<center><table BORDER=2 COLS=1 WIDTH="90%" NOSAVE >
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<tr>
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<td><tt>character(len=3) lb_method</tt>
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<br><tt>logical new</tt>
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<br><tt>integer(Zoltan_INT) num_imp, num_exp</tt>
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<br><tt>integer(Zoltan_INT) num_gid_entries, num_lid_entries </tt>
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<br><tt>integer(Zoltan_INT), pointer :: imp_procs(:), exp_procs(:)</tt>
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<br><tt>integer(Zoltan_INT), pointer :: imp_global_ids(:), exp_global_ids(:)
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! global IDs</tt>
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<br><tt>integer(Zoltan_INT), pointer :: imp_local_ids(:), exp_local_ids(:)
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! local IDs</tt>
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<br><tt>integer(Zoltan_INT) ierr</tt>
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<p><tt>! <i>Set load-balancing method.</i></tt>
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<br><tt>lb_method = "RCB"</tt>
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<br><tt>ierr = <a href="ug_interface_init.html#Zoltan_Set_Param">Zoltan_Set_Param</a>(zz, "LB_METHOD",
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lb_method)</tt>
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<p><tt>! <i>Reset some load-balancing parameters</i></tt>
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<br><tt>ierr = <a href="ug_interface_init.html#Zoltan_Set_Param">Zoltan_Set_Param</a>(zz,
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"RCB_Reuse", "TRUE")</tt>
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<p><tt>! <i>Perform computations</i></tt>
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<br><tt>...</tt>
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<br><tt>! <i>Perform load balancing</i></tt>
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<br><tt>ierr = <a href="ug_interface_lb.html#Zoltan_LB_Partition">Zoltan_LB_Partition</a>(zz,new,num_gid_entries,num_lid_entries, &</tt>
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<br><tt> num_imp,imp_global_ids,imp_local_ids,
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&</tt>
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<br><tt> imp_procs,imp_to_part, &</tt>
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<br><tt> num_exp,exp_global_ids,exp_local_ids, &</tt>
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<br><tt> exp_procs,exp_to_part) </tt>
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<br><tt>if (new) then</tt>
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<br><tt> perform_data_migration(...)</tt>
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<br><tt>endif</tt>
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<p><tt>! <i>Free memory allocated for load-balancing results by Zoltan library</i></tt>
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<br><tt>ierr = <a href="ug_interface_lb.html#Zoltan_LB_Free_Part">Zoltan_LB_Free_Part</a>(imp_global_ids, imp_local_ids, imp_procs, imp_to_part);</tt>
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<br><tt>ierr = <a href="ug_interface_lb.html#Zoltan_LB_Free_Part">Zoltan_LB_Free_Part</a>(exp_global_ids, exp_local_ids, exp_procs, exp_to_part);</tt>
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<br><tt>...</tt></td>
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</tr>
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<caption ALIGN=BOTTOM><i>Fortran version of the load-balancing example.</i></caption>
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</table></center>
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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_examples_mig.html">Next:
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Migration Examples</a> | <a href="ug_examples_init.html">Previous:
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General Usage Example</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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