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<div class="titlepage"><div><div><h5 class="title">
<a name="spirit.karma.performance_measurements.numeric_performance.double_performance"></a><a class="link" href="double_performance.html" title="Comparing the performance of a single double_ generator">
Comparing the performance of a single double_ generator</a>
</h5></div></div></div>
<p>
These performance measurements are centered around default formatting
of a single <code class="computeroutput"><span class="keyword">double</span></code> floating
point number using different libraries and methods. The overall execution
times for those examples are compared below. We compare using <code class="computeroutput"><span class="identifier">sprintf</span></code>, C++ iostreams, <a href="../../../../../../../../libs/format/index.html" target="_top">Boost.Format</a>,
and <span class="emphasis"><em>Spirit.Karma</em></span>.
</p>
<p>
For the full source code of the performance test please see here: <a href="../../../../../../optimization/karma/double_performance.cpp" target="_top">double_performance.cpp</a>.
All the measurements have been done by executing <code class="computeroutput"><span class="number">1e6</span></code>
iterations for each formatting type (NUMITERATIONS is set to <code class="computeroutput"><span class="number">1e6</span></code> in the code shown below).
</p>
<p>
Code used to measure the performance for <code class="computeroutput"><span class="identifier">sprintf</span></code>:
</p>
<p>
</p>
<pre class="programlisting"><span class="keyword">char</span> <span class="identifier">buffer</span><span class="special">[</span><span class="number">256</span><span class="special">];</span>
<span class="keyword">for</span> <span class="special">(</span><span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> <span class="identifier">i</span> <span class="special"><</span> <span class="identifier">NUMITERATIONS</span><span class="special">;</span> <span class="special">++</span><span class="identifier">i</span><span class="special">)</span> <span class="special">{</span>
<span class="identifier">sprintf</span><span class="special">(</span><span class="identifier">buffer</span><span class="special">,</span> <span class="string">"%f"</span><span class="special">,</span> <span class="number">12345.12345</span><span class="special">);</span>
<span class="special">}</span>
</pre>
<p>
</p>
<p>
Code used to measure the performance for standard C++ iostreams:
</p>
<p>
</p>
<pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">stringstream</span> <span class="identifier">strm</span><span class="special">;</span>
<span class="keyword">for</span> <span class="special">(</span><span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> <span class="identifier">i</span> <span class="special"><</span> <span class="identifier">NUMITERATIONS</span><span class="special">;</span> <span class="special">++</span><span class="identifier">i</span><span class="special">)</span> <span class="special">{</span>
<span class="identifier">strm</span><span class="special">.</span><span class="identifier">str</span><span class="special">(</span><span class="string">""</span><span class="special">);</span>
<span class="identifier">strm</span> <span class="special"><<</span> <span class="number">12345.12345</span><span class="special">;</span>
<span class="special">}</span>
</pre>
<p>
</p>
<p>
Code used to measure the performance for <a href="../../../../../../../../libs/format/index.html" target="_top">Boost.Format</a>:
</p>
<p>
</p>
<pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span> <span class="identifier">generated</span><span class="special">;</span>
<span class="identifier">boost</span><span class="special">::</span><span class="identifier">format</span> <span class="identifier">double_format</span><span class="special">(</span><span class="string">"%f"</span><span class="special">);</span>
<span class="keyword">for</span> <span class="special">(</span><span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> <span class="identifier">i</span> <span class="special"><</span> <span class="identifier">NUMITERATIONS</span><span class="special">;</span> <span class="special">++</span><span class="identifier">i</span><span class="special">)</span>
<span class="identifier">generated</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">str</span><span class="special">(</span><span class="identifier">double_format</span> <span class="special">%</span> <span class="number">12345.12345</span><span class="special">);</span>
</pre>
<p>
</p>
<p>
The following code shows the common definitions used by all <span class="emphasis"><em>Spirit.Karma</em></span>
performance measurements as listed below:
</p>
<p>
</p>
<pre class="programlisting"><span class="keyword">using</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">::</span><span class="identifier">karma</span><span class="special">::</span><span class="identifier">double_</span><span class="special">;</span>
</pre>
<p>
</p>
<p>
Code used to measure the performance for <span class="emphasis"><em>Spirit.Karma</em></span>
using a plain character buffer:
</p>
<p>
</p>
<pre class="programlisting"><span class="keyword">char</span> <span class="identifier">buffer</span><span class="special">[</span><span class="number">256</span><span class="special">];</span>
<span class="keyword">for</span> <span class="special">(</span><span class="keyword">int</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span><span class="special">;</span> <span class="identifier">i</span> <span class="special"><</span> <span class="identifier">NUMITERATIONS</span><span class="special">;</span> <span class="special">++</span><span class="identifier">i</span><span class="special">)</span> <span class="special">{</span>
<span class="keyword">char</span> <span class="special">*</span><span class="identifier">p</span> <span class="special">=</span> <span class="identifier">buffer</span><span class="special">;</span>
<span class="identifier">generate</span><span class="special">(</span><span class="identifier">p</span><span class="special">,</span> <span class="identifier">double_</span><span class="special">,</span> <span class="number">12345.12345</span><span class="special">);</span>
<span class="special">*</span><span class="identifier">p</span> <span class="special">=</span> <span class="char">'\0'</span><span class="special">;</span>
<span class="special">}</span>
</pre>
<p>
</p>
<p>
The following table shows the overall performance results collected while
using different compilers. All times are in seconds measured for <code class="computeroutput"><span class="number">1e6</span></code> iterations (platform: Windows7, Intel
Core Duo(tm) Processor, 2.8GHz, 4GByte RAM). For a more readable comparison
of the results see this <a class="link" href="double_performance.html#spirit.karma.double_performance" title="Figure 4. Performance comparison for a single double">figure</a>.
</p>
<div class="table">
<a name="id1157241"></a><p class="title"><b>Table 6. Performance comparison for a single double (all times in [s],
`1e6` iterations)</b></p>
<div class="table-contents"><table class="table" summary="Performance comparison for a single double (all times in [s],
`1e6` iterations)">
<colgroup>
<col>
<col>
<col>
<col>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
<p>
Library
</p>
</th>
<th>
<p>
gcc 4.4.0 (32 bit)
</p>
</th>
<th>
<p>
VC++ 10 (32 bit)
</p>
</th>
<th>
<p>
Intel 11.1 (32 bit)
</p>
</th>
<th>
<p>
gcc 4.4.0 (64 bit)
</p>
</th>
<th>
<p>
VC++ 10 (64 bit)
</p>
</th>
<th>
<p>
Intel 11.1 (64 bit)
</p>
</th>
</tr></thead>
<tbody>
<tr>
<td>
<p>
sprintf
</p>
</td>
<td>
<p>
0.755
</p>
</td>
<td>
<p>
0.965
</p>
</td>
<td>
<p>
0.880
</p>
</td>
<td>
<p>
0.713
</p>
</td>
<td>
<p>
0.807
</p>
</td>
<td>
<p>
0.694
</p>
</td>
</tr>
<tr>
<td>
<p>
iostreams
</p>
</td>
<td>
<p>
2.316
</p>
</td>
<td>
<p>
2.624
</p>
</td>
<td>
<p>
1.964
</p>
</td>
<td>
<p>
1.634
</p>
</td>
<td>
<p>
1.468
</p>
</td>
<td>
<p>
1.354
</p>
</td>
</tr>
<tr>
<td>
<p>
<a href="../../../../../../../../libs/format/index.html" target="_top">Boost.Format</a>
</p>
</td>
<td>
<p>
3.188
</p>
</td>
<td>
<p>
3.737
</p>
</td>
<td>
<p>
2.878
</p>
</td>
<td>
<p>
3.217
</p>
</td>
<td>
<p>
2.672
</p>
</td>
<td>
<p>
2.011
</p>
</td>
</tr>
<tr>
<td>
<p>
<span class="emphasis"><em>Spirit.Karma</em></span> double_
</p>
</td>
<td>
<p>
0.813
</p>
</td>
<td>
<p>
0.561
</p>
</td>
<td>
<p>
0.368
</p>
</td>
<td>
<p>
0.426
</p>
</td>
<td>
<p>
0.260
</p>
</td>
<td>
<p>
0.218
</p>
</td>
</tr>
</tbody>
</table></div>
</div>
<br class="table-break"><p>
</p>
<div class="figure">
<a name="spirit.karma.double_performance"></a><p class="title"><b>Figure 4. Performance comparison for a single double</b></p>
<div class="figure-contents"><span class="inlinemediaobject"><img src="../../../.././images/double_performance.png" alt="Performance comparison for a single double"></span></div>
</div>
<p><br class="figure-break">
</p>
</div>
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<td align="left"></td>
<td align="right"><div class="copyright-footer">Copyright © 2001-2010 Joel de Guzman, Hartmut Kaiser<p>
Distributed under the Boost Software License, Version 1.0. (See accompanying
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>)
</p>
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