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diff --git a/Carpet/CarpetWeb/version-4.html b/Carpet/CarpetWeb/version-4.html new file mode 100644 index 000000000..97e21c741 --- /dev/null +++ b/Carpet/CarpetWeb/version-4.html @@ -0,0 +1,220 @@ +<?xml version="1.0" encoding="ISO-8859-15"?> +<!DOCTYPE html + PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" + "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> + <head> + <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-15" /> + <title>Carpet Version 4</title> + </head> + + <body> + <h1>Carpet Version 4</h1> + + <p>Version 4 will be the next release of Carpet, which is still + under development. This page describes the current state of the + development version and lists the changes from Version 3.</p> + + <p>Main contributors to this version were, so far, + <a href="http://www.cct.lsu.edu/~eschnett/">Erik Schnetter</a> + (LSU), + <a href="http://www.aei.mpg.de/~tradke/">Thomas Radke</a> (AEI), and + <a href="http://proteus.as.arizona.edu/~cott">Christian D. Ott</a> + (UA). Special thanks go to Luca Baiotti, Denis Pollney, Christian + Reisswig, Jian Tao, and also to + the <a href="http://www.cct.lsu.edu/numerical/">CCT numerical + relativity group</a>, the <a href="http://numrel.aei.mpg.de/">AEI + numerical relativity group</a>, and + the <a href="http://www.cct.lsu.edu/~gallen/XiRelWeb/XiRel.html">XiRel + collaboration</a>.</p> + + + + <h2>Major changes</h2> + + <ul> + <li><p>The data structures and algorithms storing and handling + the communication schedule are much more efficient on large + numbers (several hundred or more) processors. This makes Carpet + scale to more than 8,000 cores.</p></li> + + <li><p>The interface for defining and making dynamic changes to + grid hierarchies is simpler, and buffer zones are handled in a + cleaner manner. This makes it easier to write user code which + defines or updates the grid hierarchy, and reduces the chance of + inconsistencies therein.</p></li> + + <li></p>During checkpointing and recovery, the grid structure is + saved and restored by default. This avoids accidental changes + upon recovery.</p></li> + + <li></p>The efficiency of I/O has been increased, especially for + HDF5 based binary I/O. It is possible to combine several + variables into one file to reduce the number of output + files.</p></li> + + <li></p>A new thorn LoopControl offers iterators over grid + points, implemented as C-style macros. These iterators allow + additional important loop-level optimisations, such + as <a href="http://en.wikipedia.org/wiki/Loop_tiling">loop + tiling</a> or + <a href="http://www.openmp.org/">OpenMP</a> parallelisation. + Efficient cache handling and hybrid communication models have a + large potential for performance improvements on current and + future architectures.</p></li> + </ul> + + + + <h2>Changes in Detail</h2> + + <h3>Initial Data</h3> + + <ul> + <li><p>The parameter <code>Carpet::enable_all_storabe</code> is + off by default, reducing memory usage. This can uncover hidden + errors in schedule.ccl files. You can use poisoning + (<code>Carpet::poison_new_timelevels = yes</code>) to find these + problems.</p></li> + + <li><p>The parameter <code>Carpet::regrid_in_level_mode</code> + is on by default. This balances the load more efficiently + between processors, especially for multi-patch + simulations.</p></li> + + <li><p>Carpet requires thorn InitBase. This allows Carpet to + check whether its handling of initial data is consistent with + other thorns, assuming that the other thorns also use InitBase. + A new parameter <code>Carpet::init_fill_timelevels</code> + instructs Carpet to initialise all past time levels by making + copies of the current time level, very similar to + what <code>MoL::initial_data_is_crap</code> does.</p></li> + + <li><p>Buffer zones are specified differently. Buffer zones are + enabled by setting <code>use_buffer_zones</code>, and outer + buffer zones are now the default. (Outer buffer zones are added + to the outside of the refined levels, instead of taking away + grid points from the interior of the refined levels.) The + necessary number of buffer zones is calculated automatically if + thorn MoL is used for time evolution.</p></li> + + <li><p>There are new schedule + bins <code>CCTK_PREREGRIDINITIAL</code> + and <code>CCTK_POSTREGRIDINITIAL</code>, called before and after + regridding during initial data setup, respectively. As a rule + of thumb, routines scheduled in <code>CCTK_BASEGRID</code> must + also be scheduled in both <code>CCTK_POSTREGRID</code> + and <code>CCTK_POSTREGRIDINITIAL</code>. You can use poisoning + (see above) to catch errors in your schedule.ccl files.</p></li> + </ul> + + <h3>Grid Structure</h3> + + <ul> + <li><p>Thorn CarpetRegrid2 stores its state in grid variables + instead of in parameters. This makes it easier to modify the + grid hierarchy from other thorns, and is automatically + consistent upon checkpointing and recovery. It also simplifies + outputting the grid structure to files. These state variables + can be modified at any time, but their values are only + significant during regridding.</p></li> + + <li><p>There is a new + parameter <code>CarpetRegrid2::symmetry_rotating180</code>, + which forces the generated grid structure to have the correct + symmetry for a 180 degree rotational symmetry about + the <code>z</code> axis. (It is unfortunate that errors in the + symmetry of the grid structure do not lead to errors but are + currently silently ignored. You can use poisoning -- see above + -- to catch errors in the grid structure.) A + parameter <code>CarpetRegrid2::symmetry_rotating90</code> is + planned, but not yet implemented.</p></li> + + <li><p>Checkpointing saves and restores the grid structure by + default.</p></li> + </ul> + + <h3>I/O</h3> + + <ul> + <li><p>All Carpet I/O thorns support the new + parameter <code>one_file_per_group</code>, which combines all + variables from a variable group into a single file. This + reduces the number of output files.</p></li> + </ul> + + <h3><Communication, Mesh Refinement</h3> + + <ul> + <li><p>The algorithm determining the communication schedule is + new and much more fussy. It will detect all (one hopes) + inconsistencies in the grid structure. (Note that this does + unfortunately not include errors regarding the outer or symmetry + boundaries.)</p></li> + + <li><p>The communication schedule is stored in a compressed + (sparse) form. This is necessary since the communication + schedule between N processors has N<sup>2</sup> entries, which + cannot be handled efficiently in full.</p></li> + + <li><p>The prolongation operators have been rewritten. Time + interpolation is now handled separately, reducing the number of + operators.</p></li> + + <li><p>Some unused CarpetLib parameters have been removed, some + new CarpetLib parameters have been introduced. The default + settings should be reasonable.</p></li> + </ul> + + <h3>New Thorns</h3> + + <ul> + <li><p>Carpet uses the new + thorn <code>CactusBase/InitBase</code>. Update from the Cactus + CVS repository to obtain this thorn.</p></li> + + <li><p>A new thorn <code>Carpet/CarpetMask</code> can be used to + exclude certain regions, such as e.g. the interior of black + holes, from global reduction operations. This allows meaningful + norms of constraints + when <a href="http://arxiv.org/abs/0707.3101">Turduckened</a> + initial data are used.</p></li> + + <li><p>Carpet offers a new thorn <code>Carpet/LoopControl</code> + providing iterators over grid points. These iterators are + implemented as C-style macros which can replace <code>for</code> + or <code>do</code> loops over grid functions. LoopControl + provides loop tiling for increased cache efficiency, and OpenMP + parallelisation to reduce parallelisation overhead on multi-core + machines.</p></li> + </ul> + + + <hr /> + + <p>Go back to the <a href=".">Carpet home page</a>.</p> + + <hr /> + + <p> + <a href="http://www.xemacs.org/About/created.html"><img + src="cbxSmall.jpg" alt="Created with XEmacs!" height="36" + width="100" /></a> + + <a href="http://www.anybrowser.org/campaign/"><img + src="logoab8.png" alt="Best Viewed With Any Browser" height="31" + width="88" /></a> + + <a href="http://validator.w3.org/check?uri=referer"><img + src="http://www.w3.org/Icons/valid-xhtml10" + alt="Valid XHTML 1.0!" height="31" width="88" /></a> + </p> + + <hr /> + <address><a href="mailto:schnetter@cct.lsu.edu">Erik Schnetter</a></address> +<!-- Created: Sat Mar 01 2008 --> +<!-- hhmts start --> +Last modified: Sat Mar 01 2008 +<!-- hhmts end --> + </body> +</html> |