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428 lines
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<title>Polly - Polyhedral optimizations for LLVM</title>
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<!--*********************************************************************-->
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<h1>About Polly</h1>
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<!--*********************************************************************-->
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<p> Polly is a high-level loop and data-locality optimizer and optimization
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infrastructure for LLVM. It uses an abstract mathematical representation based
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on integer polyhedra to analyze and optimize the memory access pattern of a
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program. We currently perform classical loop transformations, especially
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tiling and loop fusion to improve data-locality. Polly can also exploit
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OpenMP level parallelism, expose SIMDization opportunities. Work has also be
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done in the area of automatic GPU code generation.</p>
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For many users, however, it's not the existing optimizations in Polly that are
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of most interest, but the new analyses and optimizations enabled by the Polly
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infrastructure. At
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<a href="http://polyhedral.info">polyhedral.info</a> you can get an idea of
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what has already been done and what is possible in the context of polyhedral
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compilation.
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<!--=====================================================================-->
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<h2>News</h2>
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<!--=====================================================================-->
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<table id="news">
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<tr><td><b>2016</b></td></tr>
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<tr><td width="120"><p>August</p></td>
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<td>
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<a href="http://impact.gforge.inria.fr/impact2017">IMPACT 2017</a> the 7th
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International Workshop on Polyhedral Compilation Techniques will take place
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at January 23-25, 2017 together with HiPEAC 2017 in Stockholm, Sweden. It is
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a great opportunity to discuss and present work on Polyhedral Compilation,
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including work on Polly.
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</td>
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</tr>
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<tr><td width="120"><p>April</p></td>
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<td>
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A source checkout that contains Polly now provides Polly functionality
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by default in clang/opt/bugpoint without the need to load an additional
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module.
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</td>
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</tr>
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<tr><td><b>2015</b></td></tr>
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<tr><td width="120"><p>July</p></td>
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<td>
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<h4>AST Generation Paper published in TOPLAS</h4>
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The July issue of TOPLAS contains a 50 page discussion of the AST
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generation techniques used in Polly. This discussion gives not only an
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in-depth description of how we (re)generate an imperative AST from our
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polyhedral based mathematical program description, but also gives
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interesting insights about:
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<ul>
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<li><b>Schedule trees:</b> A tree-based mathematical program description
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that enables us to perform loop transformations on an abstract level,
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while issues like the generation of the correct loop structure and loop
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bounds will be taken care of by our AST generator.
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<li><b>Polyhedral unrolling:</b> We discuss techniques that allow the
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unrolling of non-trivial loops in the context of parameteric loop bounds,
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complex tile shapes and conditionally executed statements. Such unrolling
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support enables the generation of predicated code e.g. in the context of
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GPGPU computing.
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<li><b>Isolation for full/partial tile separation:</b> We discuss native
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support for handling full/partial tile separation and -- in general --
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native support for isolation of boundary cases to enable smooth code
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generation for core computations.
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<li><b>AST generation with modulo constraints:</b> We discuss how modulo
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mappings are lowered to efficient C/LLVM code.
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<li><b>User-defined constraint sets for run-time checks</b> We discuss how
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arbitrary sets of constraints can be used to automatically create run-time
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checks that ensure a set of constrainst actually hold. This feature is
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very useful to verify at run-time various assumptions that have been taken
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program optimization.
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</ul>
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<a href="http://www.grosser.es#pub-polyhedral-AST-generation">
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<em>Polyhedral AST generation is more than scanning polyhedra</em></a><br />
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Tobias Grosser, Sven Verdoolaege, Albert Cohen<br />
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ACM Transations on Programming Languages and Systems (TOPLAS), 37(4),
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July 2015
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<br>
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<br>
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<br>
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<br>
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</td>
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</tr>
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<tr><td width="120"><p>February</p></td>
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<td>
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<h4>Polly allows now non-affine subregions</h4>
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Data-dependent or floating point conditionals inside a SCoP can now be
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overapproximated in order to increase the applicability on general purpose
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code.
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</td>
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</tr>
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<tr><td><b>2014</b></td></tr>
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<tr><td width="120"><p>August</p></td>
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<td>
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<h4>Polly drops the support of ScopLib and the external optimizer PoCC</h4>
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The support for ScopLib as an exchange format has been removed as recent
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versions of clan, candl and pluto all support the OpenScop exchange format.
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The support of the external optmizer PoCC has been dropped in favor of the
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isl optimizer (default) and the still available pluto support.
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</td>
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</tr>
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<tr><td><b>2014</b></td></tr>
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<tr><td width="120"><p>June</p></td>
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<td>
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<h4>Polly can be built without GPL licensed software</h4> After Sebastian
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Pop's
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and David Peixotto's (both Qualcomm) recent <a
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href="http://repo.or.cz/w/isl.git/commit/60703e3ee89b9d5d4d1afb6a3f611292c0884574">commit</a>
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to isl, isl's latest development version can be built with imath instead of
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GMP. With both CLooG and gmp having become optional, the last obilgatory
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dependency to GPL licensed software has been removed. Now Polly only depends
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on isl (and the included imath), which are both MIT licensed.
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</td>
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</tr>
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<tr><td width="120"><p>April</p></td>
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<td>
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<h4>Polly Phone Call - 23April</h4>
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We had a polly phone call about delinearizing array accesses (II)<a
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href="https://docs.google.com/document/d/1IZewI8Up0iEkCNIPr6gVtwJxF7RV6KmXkdwOBM_Q5Cs/edit?usp=sharing ">Meeting notes</a> are available online.
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<h4>Polly Phone Call - 17th April</h4>
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We had a polly phone call about delinearizing array accesses <a
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href="https://docs.google.com/document/d/14d3ehkH2MsvBdqsEOSYjysH0Ztyzb75Lp843hnxh2IA/edit?usp=sharing">Meeting notes</a> are available online.
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<h4>Polly Phone Call - 10th April</h4>
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We had a polly phone call. <a
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href="https://docs.google.com/document/d/12W-qZjiZGEQ_lVrob4OzvKJI3EooonC-ap1b9f9KCUE/edit?usp=sharing">Meeting notes</a> are available online.
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<h4>Polly Phone Call - 4th April</h4>
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We had a polly phone call. <a
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href="https://drive.google.com/folderview?id=0B7OMOXTgCYIUWkpJbWVJcW04ams&usp=sharing">Meeting notes</a> are available online.
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</td>
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</tr>
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<tr><td width="120"><p>March</p></td>
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<td>
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<h4>Static link Polly into tools</h4> Polly can now be configured with 'cmake
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-D LINK_POLLY_INTO_TOOLS:Bool=ON' to be statically linked in the tools (opt,
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bugpoint, and clang.) This makes it easier to use polly without having to load
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a shared library, and it also reduces the complexity of compiling Polly on
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Windows.
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</td>
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</tr>
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<tr><td width="120"><p>February</p></td>
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<td>
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<h4>Polly presentation at FOSDEM 2014</h4> Polly was <a
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href="https://fosdem.org/2014/schedule/event/polly/">presented</a> at the
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FOSDEM LLVM developer's meeting.
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<h4>New LLVM test-suite buildbots</h4>
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The set of <a href="http://lab.llvm.org:8011/console?category=polly">Polly
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buildbots</a> has been extended. We now have 16 new blades that track
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correctness and performance when compiling the LLVM test-suite. For now five
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of them are used to provide <a
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href="http://llvm.org/perf/db_default/v4/nts/22463">fine granularity
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reports</a> (almost per-commit)
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for 'clang -O3' (no polly). We also have six machines that track different
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configurations of polly.
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</td>
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</tr>
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<tr><td width="120"><p>January</p></td>
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<td>
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<h4>islplot released</h4>
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<a href="https://github.com/tobig/islplot">islplot</a> is a library that
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generates illustrations of integer sets and maps. It relies on <a
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href="http://repo.or.cz/w/isl.git">isl</a> to model the integer sets and uses the <a
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href="https://pypi.python.org/pypi/islpy">islpy</a> Python bindings to access
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them. Plotting is performed with <a
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href="http://matplotlib.org">matplotlib</a>. The following <a
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href="http://nbviewer.ipython.org/github/tobig/islplot/blob/master/notebooks/islplot-examples.ipynb">
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Examples</a> show its use.
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</td>
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</tr>
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<tr><td><b>2013</b></td></tr>
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<tr><td width="120"><p>November</p></td>
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<td>
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<h4>Loop optimization BoF at upcoming LLVM conference</h4>
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At the upcoming <a href="http://llvm.org/devmtg/2013-11/#bof5">LLVM conference
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</a> there will be a loop optimization BoF discussing Polly and other high
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level loop optimizers.
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</td>
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</tr>
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<tr><td width="120"><p>October</p></td>
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<td>
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<h4>Automatic code coverage and static analysis tests</h4>
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Sylvestre Ledru set up automatic tests for <a
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href="http://buildd-clang.debian.net/coverage/">code coverage</a> and
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<a href="http://buildd-clang.debian.net/scan-build/">static analysis</a>
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which run at least once a day and which include results for Polly.
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<h4>Move to CLooG 0.18.1 and isl 0.12.1</h4>
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With the move to an isl 0.12 version Polly can be compiled without the
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need to link directly to GMP (if isl is used for code generation). Currently
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isl is still internally using GMP, but private patches exist to also remove
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this dependency. Without the use of GMP, a <b>GPL free</b> version of Polly
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is possible.
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</td></tr>
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<tr><td><b>2012</b></td></tr>
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<tr><td width="120"><p>December</p></td>
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<td>
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<h4> New publication in the PPL Journal
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</h4>
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We published a journal version of the Polly paper named
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<em>
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Polly - Performing polyhedral optimizations on a low-level intermediate
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representation</em> in the Parallel Processing Letters 2012.
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</td></tr>
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<tr><td width="120"><p>September</p></td>
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<td>
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<h4>Experimental support for the <b>new isl code generator</b></h4>
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The code generator can be parameterized on a fine-grained
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level. It gives direct control for example over unrolling, the amount of
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control overhead and the code size. It can also be used to
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create loops to handle border conditions or to perform full-partial tile
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separation.<br />
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We also relicensed isl under the <b>MIT license</b>. This means, with the
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exception of GMP (LGPL), there is no other (L)GPL licensed software used in
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Polly. The
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use of GMP is limited to a well defined interface. Replacing it with
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a BSD licensed replacement is a tractable engineering project we would
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be very interested in. For more information about isl see the <a
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href="http://www.kotnet.org/~skimo/isl/manual.pdf">isl manual</a>.
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</p>
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</td></tr>
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<tr><td width="120"><p>July</p></td>
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<td>
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<p> Polly can now be directly linked to the <a
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href="http://pluto-compiler.sourceforge.net/">Pluto optimizer</a>. We were
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already able to perform Pluto-like optimizations with Polly, as a similar
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algorithm was added to isl half a year ago. However, being able to directly
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compare with the original implementation will not only bring in competition in
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the optimizer field. It will also allow new experiments with a cutting edge
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research tool.<br \>
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This support was on of the outcomes of the 1-day Polly workshop and the
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following week of joint work at IISC Bangalore and in cooperation with
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AMD India.
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</td></tr>
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<td>
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</td></tr>
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<tr><td width="120"><p>February</p></td>
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<td>
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<p>Polly is an official LLVM project, reachable at <a
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href="http://polly.llvm.org">http://polly.llvm.org</a></p>
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</td></tr>
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<tr><td width="120"><p>January</p></td>
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<td>
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<p>Improved support for the isl scheduling optimizer</p>
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Polly can now automatically optimize all <a
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href="http://www.cse.ohio-state.edu/~pouchet/software/polybench/">polybench
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2.0</a> kernels without the help of
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an external optimizer. The compile time is reasonable and we can show
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notable speedups for various kernels.
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</td></tr>
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<tr>
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<tr><td><b><br/>2011</b></td></tr>
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<tr><td width="120"><p>November</p></td>
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<td>
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<p>
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Talk at the <a href="http://llvm.org/devmtg/2011-11/">
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LLVM Developer Meeting 2011</a></p>
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New SCEV parser<br>
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(Allows parameters in array subscript and max/signextend)
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</td></tr>
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<tr>
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<td><p>October</p></td>
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<td>
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<p>Polly can use the isl schedule optimizer<br>
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(The optimizer is similar to the one in Pluto, but it is part of isl)
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</p>
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</td></tr>
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<tr>
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<td><p>August</p></td>
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<td>
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<p>
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<a href="example_load_Polly_into_clang.html">Use Polly as
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clang plugin</a></p>
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</td>
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</tr>
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<tr>
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<td><p>July</p></td>
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<td>
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<p> Polly builder as part of the <a
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href="http://lab.llvm.org:8011/console">LLVM Buildbots</a>
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</p>
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</td>
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</tr>
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<tr>
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<td><p>June</p></td>
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<td>
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<p><a href="http://www.grosser.es">Tobias</a> is founded for
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three years by a <a
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href="http://research.google.com/university/relations/fellowship_recipients.html">
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Google Europe Fellowship in Efficient Computing</a>.
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</p>
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</td>
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</tr>
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<tr>
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<td><p>May </p></td>
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<td><p><a href="http://www.grosser.es">Tobias</a>' diploma thesis and
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Raghesh's master thesis. See our <a
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href="publications.html">list of publications</a>.</p></td>
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</tr>
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<tr>
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<td><p>April</p></td>
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<td><p>Polly moves to the LLVM infrastructure (svn, bugtracker)</p></td>
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</tr>
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<tr>
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<td><p>March</p></td>
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<td><p>Presentation at <a
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href="http://impact2011.inrialpes.fr/">CGO/IMPACT</a></p>
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<p>Polly can compile
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polybench 2.0 with vectorization and OpenMP code generation</p>
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</td>
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</tr>
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<tr>
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<td><p>Februar</p></td>
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<td><p>pollycc - a script to automatically compile with
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polyhedral optimizations </p></td>
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</tr>
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<tr>
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<td><p> Januar</p></td>
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<td><p> Basic OpenMP support, Alias analysis integration,
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Pluto/POCC support </p></td>
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</tr>
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<tr><td><b><br>2010</b></td></tr>
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<tr>
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<td><p> Dezember </p></td>
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<td><p>Basic vectorization support </p></td>
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</tr>
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<tr>
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<td><p> November </p></td>
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<td><p>Talk at the <a
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href="http://llvm.org/devmtg/2010-11/">LLVM Developer Meeting</a> </p></td>
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</tr>
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<tr>
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<td><p>October</p></td>
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<td><p>Dependency analysis </p>
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<p>Finished Phase 1 - Get something working </p>
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<p>Support scalar dependences and sequential SCoPs </p>
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</td>
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</tr>
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<tr>
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<td><p>August</p></td>
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<td><p>RegionInfo pass committed to LLVM</p>
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<p>llvm-test suite compiles </p>
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</td>
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</tr>
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<tr>
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<td><p>July</p></td>
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<td><p>Code generation works for normal SCoPs. </p></td>
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</tr>
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<tr>
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<td><p>May</p></td>
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<td><p>The CLooG AST can be parsed.</p>
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</td>
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</tr>
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<tr>
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<td><p>April</p></td>
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<td><p>SCoPs can automatically be detected. </p></td>
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</tr>
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<tr>
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<td><p>March</p></td>
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<td><p>The RegionInfo framework is almost completed. </p></td>
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</tr>
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<tr>
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<td><p>February</p></td>
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<td><p>Translate a simple loop to Polly-IR and regenerate a loop structure
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with CLooG works. </p>
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<p>ISL and CLooG are integrated. </p></td>
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</tr>
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</tr>
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<tr>
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<td><p>January</p></td>
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<td><p>The RegionInfo pass is finished. </p></td>
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</tr>
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<tr><td><b><br>2009</b></td></tr>
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<tr>
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<td><p>End of the year</p></td>
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<td><p>Work on the infrastructure started. </p></td>
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</tr>
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</table>
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</ul>
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</div>
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