ceph/src/boost/libs/math/doc/html/math_toolkit/perf_over2.html

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  26 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
  27 <a name="math_toolkit.perf_over2"></a><a class="link" href="perf_over2.html" title="Performance Overview">Performance Overview</a>
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  29 <p>
  30       By and large the performance of this library should be acceptable for most
  31       needs. However, often the library has to make a choice whether to be accurate
  32       or fast and by default it chooses accuracy over speed. If you would rather
  33       have fast rather than fully accurate routines, then refer to the <a class="link" href="../perf.html" title="Chapter&#160;16.&#160;Performance">performance
  34       section</a> for information and examples on how to achieve this.
  35     </p>
  36 <p>
  37       In terms of the algorithms used, this library aims to use the same "best
  38       of breed" algorithms as many other libraries: the principle difference
  39       is that this library is implemented in C++ - taking advantage of all the abstraction
  40       mechanisms that C++ offers - where as most traditional numeric libraries are
  41       implemented in C or FORTRAN. Traditionally languages such as C or FORTRAN are
  42       perceived as easier to optimise than more complex languages like C++, so in
  43       a sense this library provides a good test of current compiler technology, and
  44       the "abstraction penalty" - if any - of C++ compared to other languages.
  45     </p>
  46 <p>
  47       The three most important things you can do to ensure the best performance from
  48       this library are:
  49     </p>
  50 <div class="orderedlist"><ol class="orderedlist" type="1">
  51 <li class="listitem">
  52           Turn on your compilers optimisations: the difference between "release"
  53           and "debug" builds can easily be a <a class="link" href="getting_best.html" title="Getting the Best Performance from this Library: Compiler and Compiler Options">factor
  54           of 20</a>.
  55         </li>
  56 <li class="listitem">
  57           Pick your compiler carefully: <a class="link" href="comp_compilers.html" title="Comparing Different Compilers">performance
  58           differences of up to 8 fold</a> have been found between some Windows
  59           compilers for example.
  60         </li>
  61 <li class="listitem">
  62           Disable internal use of <code class="computeroutput"><span class="keyword">long</span> <span class="keyword">double</span></code>, this will reduce accuracy but typically
  63           yield a 2x speedup on modern x64 hardware/compilers.
  64         </li>
  65 </ol></div>
  66 <p>
  67       The <a class="link" href="../perf.html" title="Chapter&#160;16.&#160;Performance">performance section</a> contains more information
  68       on the performance of this library, what you can do to fine tune it, and how
  69       this library compares to some other open source alternatives.
  70     </p>
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  74 <td align="right"><div class="copyright-footer">Copyright &#169; 2006-2010, 2012-2014 Nikhar Agrawal,
  75       Anton Bikineev, Paul A. Bristow, Marco Guazzone, Christopher Kormanyos, Hubert
  76       Holin, Bruno Lalande, John Maddock, Jeremy Murphy, Johan R&#229;de, Gautam Sewani,
  77       Benjamin Sobotta, Thijs van den Berg, Daryle Walker and Xiaogang Zhang<p>
  78         Distributed under the Boost Software License, Version 1.0. (See accompanying
  79         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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