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<div class="title">list_partition.h</div> </div>
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<a href="a00923.html">Go to the documentation of this file.</a><div class="fragment"><pre class="fragment"><a name="l00001"></a>00001 <span class="comment">// -*- C++ -*-</span>
<a name="l00002"></a>00002
<a name="l00003"></a>00003 <span class="comment">// Copyright (C) 2007, 2008, 2009 Free Software Foundation, Inc.</span>
<a name="l00004"></a>00004 <span class="comment">//</span>
<a name="l00005"></a>00005 <span class="comment">// This file is part of the GNU ISO C++ Library. This library is free</span>
<a name="l00006"></a>00006 <span class="comment">// software; you can redistribute __it and/or modify __it under the terms</span>
<a name="l00007"></a>00007 <span class="comment">// of the GNU General Public License as published by the Free Software</span>
<a name="l00008"></a>00008 <span class="comment">// Foundation; either version 3, or (at your option) any later</span>
<a name="l00009"></a>00009 <span class="comment">// version.</span>
<a name="l00010"></a>00010
<a name="l00011"></a>00011 <span class="comment">// This library is distributed in the hope that __it will be useful, but</span>
<a name="l00012"></a>00012 <span class="comment">// WITHOUT ANY WARRANTY; without even the implied warranty of</span>
<a name="l00013"></a>00013 <span class="comment">// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU</span>
<a name="l00014"></a>00014 <span class="comment">// General Public License for more details.</span>
<a name="l00015"></a>00015
<a name="l00016"></a>00016 <span class="comment">// Under Section 7 of GPL version 3, you are granted additional</span>
<a name="l00017"></a>00017 <span class="comment">// permissions described in the GCC Runtime Library Exception, version</span>
<a name="l00018"></a>00018 <span class="comment">// 3.1, as published by the Free Software Foundation.</span>
<a name="l00019"></a>00019
<a name="l00020"></a>00020 <span class="comment">// You should have received a copy of the GNU General Public License and</span>
<a name="l00021"></a>00021 <span class="comment">// a copy of the GCC Runtime Library Exception along with this program;</span>
<a name="l00022"></a>00022 <span class="comment">// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see</span>
<a name="l00023"></a>00023 <span class="comment">// <http://www.gnu.org/licenses/>.</span>
<a name="l00024"></a>00024 <span class="comment"></span>
<a name="l00025"></a>00025 <span class="comment">/** @file parallel/list_partition.h</span>
<a name="l00026"></a>00026 <span class="comment"> * @brief _Functionality to split __sequence referenced by only input</span>
<a name="l00027"></a>00027 <span class="comment"> * iterators.</span>
<a name="l00028"></a>00028 <span class="comment"> * This file is a GNU parallel extension to the Standard C++ Library.</span>
<a name="l00029"></a>00029 <span class="comment"> */</span>
<a name="l00030"></a>00030
<a name="l00031"></a>00031 <span class="comment">// Written by Leonor Frias Moya and Johannes Singler.</span>
<a name="l00032"></a>00032
<a name="l00033"></a>00033 <span class="preprocessor">#ifndef _GLIBCXX_PARALLEL_LIST_PARTITION_H</span>
<a name="l00034"></a>00034 <span class="preprocessor"></span><span class="preprocessor">#define _GLIBCXX_PARALLEL_LIST_PARTITION_H 1</span>
<a name="l00035"></a>00035 <span class="preprocessor"></span>
<a name="l00036"></a>00036 <span class="preprocessor">#include <<a class="code" href="a00971.html" title="End-user include file. Provides advanced settings and tuning options. This file is a GNU parallel ext...">parallel/parallel.h</a>></span>
<a name="l00037"></a>00037 <span class="preprocessor">#include <vector></span>
<a name="l00038"></a>00038
<a name="l00039"></a>00039 <span class="keyword">namespace </span>__gnu_parallel
<a name="l00040"></a>00040 {<span class="comment"></span>
<a name="l00041"></a>00041 <span class="comment"> /** @brief Shrinks and doubles the ranges.</span>
<a name="l00042"></a>00042 <span class="comment"> * @param __os_starts Start positions worked on (oversampled).</span>
<a name="l00043"></a>00043 <span class="comment"> * @param __count_to_two Counts up to 2.</span>
<a name="l00044"></a>00044 <span class="comment"> * @param __range_length Current length of a chunk.</span>
<a name="l00045"></a>00045 <span class="comment"> * @param __make_twice Whether the @c __os_starts is allowed to be</span>
<a name="l00046"></a>00046 <span class="comment"> * grown or not</span>
<a name="l00047"></a>00047 <span class="comment"> */</span>
<a name="l00048"></a>00048 <span class="keyword">template</span><<span class="keyword">typename</span> _IIter>
<a name="l00049"></a>00049 <span class="keywordtype">void</span>
<a name="l00050"></a><a class="code" href="a01131.html#a83520999694f488a985b6b95cd021c70">00050</a> <a class="code" href="a01131.html#a83520999694f488a985b6b95cd021c70" title="Shrinks and doubles the ranges.">__shrink_and_double</a>(<a class="code" href="a00739.html" title="A standard container which offers fixed time access to individual elements in any order...">std::vector<_IIter></a>& __os_starts,
<a name="l00051"></a>00051 <span class="keywordtype">size_t</span>& __count_to_two, <span class="keywordtype">size_t</span>& __range_length,
<a name="l00052"></a>00052 <span class="keyword">const</span> <span class="keywordtype">bool</span> __make_twice)
<a name="l00053"></a>00053 {
<a name="l00054"></a>00054 ++__count_to_two;
<a name="l00055"></a>00055 <span class="keywordflow">if</span> (!__make_twice || __count_to_two < 2)
<a name="l00056"></a>00056 <a class="code" href="a01131.html#aa53ee9360db21a409e8249af8bb9dc4c" title="Combines two ranges into one and thus halves the number of ranges.">__shrink</a>(__os_starts, __count_to_two, __range_length);
<a name="l00057"></a>00057 <span class="keywordflow">else</span>
<a name="l00058"></a>00058 {
<a name="l00059"></a>00059 __os_starts.<a class="code" href="a00739.html#a1134bcc83ff6c70cf78bab3cd426feaf" title="Resizes the vector to the specified number of elements.">resize</a>((__os_starts.<a class="code" href="a00739.html#a49e9afae414f8d8e3a2e1221c3a050c6">size</a>() - 1) * 2 + 1);
<a name="l00060"></a>00060 __count_to_two = 0;
<a name="l00061"></a>00061 }
<a name="l00062"></a>00062 }
<a name="l00063"></a>00063 <span class="comment"></span>
<a name="l00064"></a>00064 <span class="comment"> /** @brief Combines two ranges into one and thus halves the number of ranges.</span>
<a name="l00065"></a>00065 <span class="comment"> * @param __os_starts Start positions worked on (oversampled).</span>
<a name="l00066"></a>00066 <span class="comment"> * @param __count_to_two Counts up to 2.</span>
<a name="l00067"></a>00067 <span class="comment"> * @param __range_length Current length of a chunk. */</span>
<a name="l00068"></a>00068 <span class="keyword">template</span><<span class="keyword">typename</span> _IIter>
<a name="l00069"></a>00069 <span class="keywordtype">void</span>
<a name="l00070"></a><a class="code" href="a01131.html#aa53ee9360db21a409e8249af8bb9dc4c">00070</a> <a class="code" href="a01131.html#aa53ee9360db21a409e8249af8bb9dc4c" title="Combines two ranges into one and thus halves the number of ranges.">__shrink</a>(<a class="code" href="a00739.html" title="A standard container which offers fixed time access to individual elements in any order...">std::vector<_IIter></a>& __os_starts, <span class="keywordtype">size_t</span>& __count_to_two,
<a name="l00071"></a>00071 <span class="keywordtype">size_t</span>& __range_length)
<a name="l00072"></a>00072 {
<a name="l00073"></a>00073 <span class="keywordflow">for</span> (<span class="keyword">typename</span> std::vector<_IIter>::size_type __i = 0;
<a name="l00074"></a>00074 __i <= (__os_starts.<a class="code" href="a00739.html#a49e9afae414f8d8e3a2e1221c3a050c6">size</a>() / 2); ++__i)
<a name="l00075"></a>00075 __os_starts[__i] = __os_starts[__i * 2];
<a name="l00076"></a>00076 __range_length *= 2;
<a name="l00077"></a>00077 }
<a name="l00078"></a>00078 <span class="comment"></span>
<a name="l00079"></a>00079 <span class="comment"> /** @brief Splits a sequence given by input iterators into parts of</span>
<a name="l00080"></a>00080 <span class="comment"> * almost equal size</span>
<a name="l00081"></a>00081 <span class="comment"> *</span>
<a name="l00082"></a>00082 <span class="comment"> * The function needs only one pass over the sequence.</span>
<a name="l00083"></a>00083 <span class="comment"> * @param __begin Begin iterator of input sequence.</span>
<a name="l00084"></a>00084 <span class="comment"> * @param __end End iterator of input sequence.</span>
<a name="l00085"></a>00085 <span class="comment"> * @param __starts Start iterators for the resulting parts, dimension</span>
<a name="l00086"></a>00086 <span class="comment"> * @c __num_parts+1. For convenience, @c __starts @c [__num_parts]</span>
<a name="l00087"></a>00087 <span class="comment"> * contains the end iterator of the sequence.</span>
<a name="l00088"></a>00088 <span class="comment"> * @param __lengths Length of the resulting parts.</span>
<a name="l00089"></a>00089 <span class="comment"> * @param __num_parts Number of parts to split the sequence into.</span>
<a name="l00090"></a>00090 <span class="comment"> * @param __f Functor to be applied to each element by traversing __it</span>
<a name="l00091"></a>00091 <span class="comment"> * @param __oversampling Oversampling factor. If 0, then the</span>
<a name="l00092"></a>00092 <span class="comment"> * partitions will differ in at most </span>
<a name="l00093"></a>00093 <span class="comment"> * \sqrt{\mathrm{__end} - \mathrm{__begin}} </span>
<a name="l00094"></a>00094 <span class="comment"> * __elements. Otherwise, the ratio between the</span>
<a name="l00095"></a>00095 <span class="comment"> * longest and the shortest part is bounded by</span>
<a name="l00096"></a>00096 <span class="comment"> * 1/(\mathrm{__oversampling} \cdot \mathrm{num\_parts})</span>
<a name="l00097"></a>00097 <span class="comment"> * @return Length of the whole sequence.</span>
<a name="l00098"></a>00098 <span class="comment"> */</span>
<a name="l00099"></a>00099 <span class="keyword">template</span><<span class="keyword">typename</span> _IIter, <span class="keyword">typename</span> _FunctorType>
<a name="l00100"></a>00100 <span class="keywordtype">size_t</span>
<a name="l00101"></a><a class="code" href="a01131.html#a766c833a89b35bc0c89fd2b7bd7e1c1a">00101</a> <a class="code" href="a01131.html#a766c833a89b35bc0c89fd2b7bd7e1c1a" title="Splits a sequence given by input iterators into parts of almost equal size.">list_partition</a>(<span class="keyword">const</span> _IIter __begin, <span class="keyword">const</span> _IIter __end,
<a name="l00102"></a>00102 _IIter* __starts, <span class="keywordtype">size_t</span>* __lengths, <span class="keyword">const</span> <span class="keywordtype">int</span> __num_parts,
<a name="l00103"></a>00103 _FunctorType& __f, <span class="keywordtype">int</span> __oversampling = 0)
<a name="l00104"></a>00104 {
<a name="l00105"></a>00105 <span class="keywordtype">bool</span> __make_twice = <span class="keyword">false</span>;
<a name="l00106"></a>00106
<a name="l00107"></a>00107 <span class="comment">// The resizing algorithm is chosen according to the oversampling factor.</span>
<a name="l00108"></a>00108 <span class="keywordflow">if</span> (__oversampling == 0)
<a name="l00109"></a>00109 {
<a name="l00110"></a>00110 __make_twice = <span class="keyword">true</span>;
<a name="l00111"></a>00111 __oversampling = 1;
<a name="l00112"></a>00112 }
<a name="l00113"></a>00113
<a name="l00114"></a>00114 <a class="code" href="a00739.html" title="A standard container which offers fixed time access to individual elements in any order...">std::vector<_IIter></a> __os_starts(2 * __oversampling * __num_parts + 1);
<a name="l00115"></a>00115
<a name="l00116"></a>00116 __os_starts[0] = __begin;
<a name="l00117"></a>00117 _IIter __prev = __begin, __it = __begin;
<a name="l00118"></a>00118 <span class="keywordtype">size_t</span> __dist_limit = 0, __dist = 0;
<a name="l00119"></a>00119 <span class="keywordtype">size_t</span> __cur = 1, __next = 1;
<a name="l00120"></a>00120 <span class="keywordtype">size_t</span> __range_length = 1;
<a name="l00121"></a>00121 <span class="keywordtype">size_t</span> __count_to_two = 0;
<a name="l00122"></a>00122 <span class="keywordflow">while</span> (__it != __end)
<a name="l00123"></a>00123 {
<a name="l00124"></a>00124 __cur = __next;
<a name="l00125"></a>00125 <span class="keywordflow">for</span> (; __cur < __os_starts.<a class="code" href="a00739.html#a49e9afae414f8d8e3a2e1221c3a050c6">size</a>() and __it != __end; ++__cur)
<a name="l00126"></a>00126 {
<a name="l00127"></a>00127 <span class="keywordflow">for</span> (__dist_limit += __range_length;
<a name="l00128"></a>00128 __dist < __dist_limit and __it != __end; ++__dist)
<a name="l00129"></a>00129 {
<a name="l00130"></a>00130 __f(__it);
<a name="l00131"></a>00131 ++__it;
<a name="l00132"></a>00132 }
<a name="l00133"></a>00133 __os_starts[__cur] = __it;
<a name="l00134"></a>00134 }
<a name="l00135"></a>00135
<a name="l00136"></a>00136 <span class="comment">// Must compare for end and not __cur < __os_starts.size() , because</span>
<a name="l00137"></a>00137 <span class="comment">// __cur could be == __os_starts.size() as well</span>
<a name="l00138"></a>00138 <span class="keywordflow">if</span> (__it == __end)
<a name="l00139"></a>00139 <span class="keywordflow">break</span>;
<a name="l00140"></a>00140
<a name="l00141"></a>00141 <a class="code" href="a01131.html#a83520999694f488a985b6b95cd021c70" title="Shrinks and doubles the ranges.">__shrink_and_double</a>(__os_starts, __count_to_two, __range_length,
<a name="l00142"></a>00142 __make_twice);
<a name="l00143"></a>00143 __next = __os_starts.<a class="code" href="a00739.html#a49e9afae414f8d8e3a2e1221c3a050c6">size</a>() / 2 + 1;
<a name="l00144"></a>00144 }
<a name="l00145"></a>00145
<a name="l00146"></a>00146 <span class="comment">// Calculation of the parts (one must be extracted from __current</span>
<a name="l00147"></a>00147 <span class="comment">// because the partition beginning at end, consists only of</span>
<a name="l00148"></a>00148 <span class="comment">// itself).</span>
<a name="l00149"></a>00149 <span class="keywordtype">size_t</span> __size_part = (__cur - 1) / __num_parts;
<a name="l00150"></a>00150 <span class="keywordtype">int</span> __size_greater = <span class="keyword">static_cast<</span><span class="keywordtype">int</span><span class="keyword">></span>((__cur - 1) % __num_parts);
<a name="l00151"></a>00151 __starts[0] = __os_starts[0];
<a name="l00152"></a>00152
<a name="l00153"></a>00153 <span class="keywordtype">size_t</span> __index = 0;
<a name="l00154"></a>00154
<a name="l00155"></a>00155 <span class="comment">// Smallest partitions.</span>
<a name="l00156"></a>00156 <span class="keywordflow">for</span> (<span class="keywordtype">int</span> __i = 1; __i < (__num_parts + 1 - __size_greater); ++__i)
<a name="l00157"></a>00157 {
<a name="l00158"></a>00158 __lengths[__i - 1] = __size_part * __range_length;
<a name="l00159"></a>00159 __index += __size_part;
<a name="l00160"></a>00160 __starts[__i] = __os_starts[__index];
<a name="l00161"></a>00161 }
<a name="l00162"></a>00162
<a name="l00163"></a>00163 <span class="comment">// Biggest partitions.</span>
<a name="l00164"></a>00164 <span class="keywordflow">for</span> (<span class="keywordtype">int</span> __i = __num_parts + 1 - __size_greater; __i <= __num_parts;
<a name="l00165"></a>00165 ++__i)
<a name="l00166"></a>00166 {
<a name="l00167"></a>00167 __lengths[__i - 1] = (__size_part+1) * __range_length;
<a name="l00168"></a>00168 __index += (__size_part+1);
<a name="l00169"></a>00169 __starts[__i] = __os_starts[__index];
<a name="l00170"></a>00170 }
<a name="l00171"></a>00171
<a name="l00172"></a>00172 <span class="comment">// Correction of the end size (the end iteration has not finished).</span>
<a name="l00173"></a>00173 __lengths[__num_parts - 1] -= (__dist_limit - __dist);
<a name="l00174"></a>00174
<a name="l00175"></a>00175 <span class="keywordflow">return</span> __dist;
<a name="l00176"></a>00176 }
<a name="l00177"></a>00177 }
<a name="l00178"></a>00178
<a name="l00179"></a>00179 <span class="preprocessor">#endif </span><span class="comment">/* _GLIBCXX_PARALLEL_LIST_PARTITION_H */</span>
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