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<title>Performance / Compilers</title><meta name="generator" content="DocBook XSL-NS Stylesheets V1.75.2"><link rel="home" href="index.html" title="Meta State Machine (MSM)"><link rel="up" href="index.html" title="Meta State Machine (MSM)"><link rel="prev" href="ar01s04.html" title="User's Guide"><link rel="next" href="ar01s06.html" title="Questions & Answers"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center"> Performance / Compilers</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ar01s04.html">Prev</a> </td><th width="60%" align="center"> </th><td width="20%" align="right"> <a accesskey="n" href="ar01s06.html">Next</a></td></tr></table><hr></div><div class="sect1" title="Performance / Compilers"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="d0e3639"></a> Performance / Compilers</h2></div></div></div><p>Tests were made on different PCs running Windows XP and Vista and compiled with VC9
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SP1 or Ubuntu and compiled with g++ 4.2 and 4.3. For these tests, the same player state
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machine was written using Boost.Statechart, as a <a class="link" href="examples/SC Simple.cpp" target="_top">state machine with only simple states</a> and
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as a <a class="link" href="examples/SC Composite.cpp" target="_top">state machine with a composite
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state</a>. The same simple and composite state machines are implemented with MSM
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with a standard frontend <a class="link" href="examples/MsmSimple.cpp" target="_top">(simple)</a><a class="link" href="examples/MsmComposite.cpp" target="_top">(composite)</a>, the simple one also with
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<a class="link" href="examples/MsmSimpleFunctors.cpp" target="_top">functors</a> and with <a class="link" href="examples/EumlSimple.cpp" target="_top">eUML</a>. As these simple machines need no
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terminate/interrupt states, no message queue and have no-throw guarantee on their
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actions, the MSM state machines are defined with minimum functionality.</p><div class="sect2" title="Speed"><div class="titlepage"><div><div><h3 class="title"><a name="d0e3661"></a>Speed</h3></div></div></div><p>VC9:</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>The simple test completes 36 times faster with Msm than with
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Boost.Statechart</p></li><li class="listitem"><p>The composite test completes 18 times faster with MSM</p></li><li class="listitem"><p>The fastest version is with eUML/functors. It completes 58 times
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faster than Boost.Statechart. A transition costs 4.5ns on a
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Q6600.</p></li></ul></div><p>gcc 4.2.3:</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>The simple test completes 54 times faster with Msm (with
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functors)</p></li><li class="listitem"><p>The composite test completes 25 times faster with Msm</p></li></ul></div></div><div class="sect2" title="Executable size"><div class="titlepage"><div><div><h3 class="title"><a name="d0e3685"></a>Executable size</h3></div></div></div><p>There are some worries that MSM generates huge code. Is it true? The 2 compilers I
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tested disagree with this claim. On VC9, the test state machines used in the
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performance section produce executables of 14kB (for simple and eUML) and 21kB (for
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the composite). This includes the test code and iostreams. By comparison, an empty
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executable with iostreams generated by VC9 has a size of 7kB. Boost.Statechart
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generates executables of 43kB and 54kB. As a bonus, eUML comes for “free” in terms
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of executable size. You even get a speed gain. With g++ 4.3, it strongly depends on
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the compiler options (much more than VC). A good size state machine with –O3 can
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generate an executable of 600kB, and with eUML you can get to 1.5MB. Trying with –Os
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–s I come down to 18kB and 30kB for the test state machines, while eUML will go down
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to 1MB (which is still big), so in this case eUML does not come for free.</p></div><div class="sect2" title="Supported compilers"><div class="titlepage"><div><div><h3 class="title"><a name="d0e3690"></a>Supported compilers</h3></div></div></div><p> MSM was successfully tested with: </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>VC8 (please read further), VC9SP1, VC10 Beta 1 and 2</p></li><li class="listitem"><p>g++ 4.1 and higher</p></li><li class="listitem"><p>Green Hills Software MULTI for ARM v5.0.5 patch 4416 (Simple and
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Composite tutorials)</p></li></ul></div><p> eUML will only work with: </p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>VC8 (partly). You cannot, however use any overloaded function (like
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splice) and compile times and RAM consumption explode</p></li><li class="listitem"><p>VC9SP1, VC10 Beta1-2</p></li><li class="listitem"><p>g++ 4.3 and higher (previous versions lack native typeof
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support)</p></li></ul></div><p>VC8 and to some lesser extent VC9 suffer from a bug. Enabling the option "Enable
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Minimal Rebuild" (/Gm) will cause much higher compile-time (up to three times with
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VC8!). This option being activated per default in Debug mode, this can be a big
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problem.</p></div><div class="sect2" title="Limitations"><div class="titlepage"><div><div><h3 class="title"><a name="d0e3719"></a> Limitations </h3></div></div></div><p>
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</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Compilation times of state machines with > 80 transitions that are
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going to make you storm the CFO's office and make sure you get a shiny
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octocore with 8GB RAM by next week, unless he's interested in paying you
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watch the compiler agonize for hours... (Make sure you ask for dual 24"
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as well, it doesn't hurt).</p></li><li class="listitem"><p>eUML allows very long constructs but will also quickly increase your
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compile time on some compilers (VC9, VC10 Beta1) with buggy decltype
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support (I suspect some at least quadratic algorithms there). Even g++
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4.4 shows some regression compared to 4.3 and will crash if the
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constructs become too big.</p></li><li class="listitem"><p>Need to overwrite the mpl::vector/list default-size-limit of 20 and
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fusion default vector size of 10 if more than 10 states found in a state
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machine</p></li></ul></div><p>
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</p></div><div class="sect2" title="Compilers corner"><div class="titlepage"><div><div><h3 class="title"><a name="d0e3735"></a> Compilers corner </h3></div></div></div><p>Compilers are sometimes full of surprises and such strange errors happened in the
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course of the development that I wanted to list the most fun for readers’
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entertainment.</p><p><span class="underline">VC8</span>: </p><p><code class="code">template <class StateType> </code></p><p><code class="code">typename ::boost::enable_if< </code></p><p><code class="code">typename ::boost::mpl::and_<</code></p><p><code class="code">typename ::boost::mpl::not_<typename
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has_exit_pseudo_states<StateType>::type>::type, </code></p><p><code class="code">typename ::boost::mpl::not_<typename
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is_pseudo_exit<StateType>::type>::type >::type,BaseState*>::type
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</code></p><p>I get the following error:</p><p>error C2770: invalid explicit template argument(s) for '`global
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namespace'::boost::enable_if<is_pseudo_exit<StateType>::type,BaseState*>::type
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boost::msm::state_machine<Derived,HistoryPolicy,BaseState>::add_state<ContainingSM>::new_state_helper(boost::msm::dummy<__formal>)
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const' </p><p>If I now remove the first “::” in ::boost::mpl , the compiler shuts up. So in this
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case, it is not possible to follow Boost’s guidelines.</p><p><span class="underline">VC9</span>:</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>This one is my all times’ favorite. Do you know why the exit pseudo
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states are referenced in the transition table with a
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“submachine::exit_pt” ? Because “exit” will crash the compiler. “Exit”
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is not possible either because it will crash the compiler on one
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machine, but not on another (the compiler was installed from the same
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disk).</p></li><li class="listitem"><p>Sometimes, removing a policy crashes the compiler, so some versions
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are defining a dummy policy called WorkaroundVC9.</p></li><li class="listitem"><p>Typeof: While g++ and VC9 compile “standard” state machines in
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comparable times, Typeof (while in both ways natively supported) seems
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to behave in a quadratic complexity with VC9 and VC10.</p></li><li class="listitem"><p>eUML: in case of a compiler crash, changing the order of state
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definitions (first states without entry or exit) sometimes solves the
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problem.</p></li></ul></div><p><span class="underline">g++ 4.x</span>: Boring compiler, almost all is
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working almost as expected. Being not a language lawyer I am unsure about the
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following “Typeof problem”. VC9 and g++ disagree on the question if you can derive
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from the BOOST_TYPEOF generated type without first defining a typedef. I will be
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thankful for an answer on this. I only found two ways to break the compiler:</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p>Add more eUML constructs until something explodes (especially with
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g++-4.4) </p></li><li class="listitem"><p>The build_terminate function uses 2 mpl::push_back instead of
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mpl::insert_range because g++ would not accept insert_range.</p></li></ul></div><p>You can test your compiler’s decltype implementation with the <a class="link" href="examples/CompilerStressTestEuml.cpp" target="_top">following stress test</a>
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and reactivate the commented-out code until the compiler crashes.</p></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ar01s04.html">Prev</a> </td><td width="20%" align="center"> </td><td width="40%" align="right"> <a accesskey="n" href="ar01s06.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">User's Guide </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Questions & Answers</td></tr></table></div></body></html> |