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<compoundname>cudaFlowSort</compoundname>

<title>Parallel Sort</title>

<tableofcontents/>

<briefdescription>

</briefdescription>

<detaileddescription>

<para>cudaFlow provides template methods to create parallel sort tasks on a CUDA GPU.</para><sect1 id="cudaFlowSort_1cudaFlowSortARangeofItems">

<title>Sort a Range of Items</title>

<para><ref refid="classtf_1_1cudaFlow_1ae462d455fed06dfcdbd1e25a2c9c5da6" kindref="member">tf::cudaFlow::sort</ref> performs an in-place parallel sort over a range of elements specified by <computeroutput>[first, last)</computeroutput> using the given comparator. The following code sorts one million random integers in an increasing order on a GPU.</para><para><programlisting filename=".cpp"><codeline><highlight class="keyword">const</highlight><highlight class="normal"><sp/></highlight><highlight class="keywordtype">size_t</highlight><highlight class="normal"><sp/>N<sp/>=<sp/>1000000;</highlight></codeline>

<codeline><highlight class="normal"></highlight><highlight class="keywordtype">int</highlight><highlight class="normal">*<sp/>vec<sp/>=<sp/>tf::cuda_malloc_shared&lt;int&gt;(N);<sp/><sp/></highlight><highlight class="comment">//<sp/>vector</highlight><highlight class="normal"></highlight></codeline>

<codeline><highlight class="normal"></highlight></codeline>

<codeline><highlight class="normal"></highlight><highlight class="comment">//<sp/>initializes<sp/>the<sp/>data</highlight><highlight class="normal"></highlight></codeline>

<codeline><highlight class="normal"></highlight><highlight class="keywordflow">for</highlight><highlight class="normal">(</highlight><highlight class="keywordtype">size_t</highlight><highlight class="normal"><sp/>i=0;<sp/>i&lt;N;<sp/>i++)<sp/></highlight></codeline>

<codeline><highlight class="normal"><sp/><sp/>vec[i]<sp/>=<sp/><ref refid="cpp/numeric/random/rand" kindref="compound" external="/home/twhuang/Code/taskflow/doxygen/cppreference-doxygen-web.tag.xml">rand</ref>();</highlight></codeline>

<codeline><highlight class="normal">}<sp/></highlight></codeline>

<codeline><highlight class="normal"></highlight></codeline>

<codeline><highlight class="normal"></highlight><highlight class="comment">//<sp/>create<sp/>a<sp/>cudaFlow<sp/>of<sp/>one<sp/>task<sp/>to<sp/>perform<sp/>parallel<sp/>sort</highlight><highlight class="normal"></highlight></codeline>

<codeline><highlight class="normal"><ref refid="classtf_1_1cudaFlow" kindref="compound">tf::cudaFlow</ref><sp/>cf;</highlight></codeline>

<codeline><highlight class="normal"><ref refid="classtf_1_1cudaTask" kindref="compound">tf::cudaTask</ref><sp/>task<sp/>=<sp/>cf.<ref refid="classtf_1_1cudaFlow_1ae462d455fed06dfcdbd1e25a2c9c5da6" kindref="member">sort</ref>(vec,<sp/>vec<sp/>+<sp/>N);</highlight></codeline>

<codeline><highlight class="normal">cf.<ref refid="classtf_1_1cudaFlow_1a85789ed8a1f47704cf1f1a2b98969444" kindref="member">offload</ref>();</highlight></codeline>

<codeline><highlight class="normal"></highlight></codeline>

<codeline><highlight class="normal">assert(std::is_sorted(vec,<sp/>vec+N));</highlight></codeline>

</programlisting></para><para>You can specify a comparator to <ref refid="classtf_1_1cudaFlow_1ae462d455fed06dfcdbd1e25a2c9c5da6" kindref="member">tf::cudaFlow::sort</ref> to alter the sorting order. For example, the following code sorts one million random integers in an decreasing order on a GPU.</para><para><programlisting filename=".cpp"><codeline><highlight class="keyword">const</highlight><highlight class="normal"><sp/></highlight><highlight class="keywordtype">size_t</highlight><highlight class="normal"><sp/>N<sp/>=<sp/>1000000;</highlight></codeline>

<codeline><highlight class="normal"></highlight><highlight class="keywordtype">int</highlight><highlight class="normal">*<sp/>vec<sp/>=<sp/>tf::cuda_malloc_shared&lt;int&gt;(N);<sp/><sp/></highlight><highlight class="comment">//<sp/>vector</highlight><highlight class="normal"></highlight></codeline>

<codeline><highlight class="normal"></highlight></codeline>

<codeline><highlight class="normal"></highlight><highlight class="comment">//<sp/>initializes<sp/>the<sp/>data</highlight><highlight class="normal"></highlight></codeline>

<codeline><highlight class="normal"></highlight><highlight class="keywordflow">for</highlight><highlight class="normal">(</highlight><highlight class="keywordtype">size_t</highlight><highlight class="normal"><sp/>i=0;<sp/>i&lt;N;<sp/>i++)<sp/></highlight></codeline>

<codeline><highlight class="normal"><sp/><sp/>vec[i]<sp/>=<sp/><ref refid="cpp/numeric/random/rand" kindref="compound" external="/home/twhuang/Code/taskflow/doxygen/cppreference-doxygen-web.tag.xml">rand</ref>();</highlight></codeline>

<codeline><highlight class="normal">}<sp/></highlight></codeline>

<codeline><highlight class="normal"></highlight></codeline>

<codeline><highlight class="normal"></highlight><highlight class="comment">//<sp/>create<sp/>a<sp/>cudaFlow<sp/>of<sp/>one<sp/>task<sp/>to<sp/>perform<sp/>parallel<sp/>sort</highlight><highlight class="normal"></highlight></codeline>

<codeline><highlight class="normal"><ref refid="classtf_1_1cudaFlow" kindref="compound">tf::cudaFlow</ref><sp/>cf;</highlight></codeline>

<codeline><highlight class="normal"><ref refid="classtf_1_1cudaTask" kindref="compound">tf::cudaTask</ref><sp/>task<sp/>=<sp/>cf.<ref refid="classtf_1_1cudaFlow_1ae462d455fed06dfcdbd1e25a2c9c5da6" kindref="member">sort</ref>(</highlight></codeline>

<codeline><highlight class="normal"><sp/><sp/>vec,<sp/>vec<sp/>+<sp/>N,<sp/>[]<sp/>__device__<sp/>(</highlight><highlight class="keywordtype">int</highlight><highlight class="normal"><sp/>a,<sp/></highlight><highlight class="keywordtype">int</highlight><highlight class="normal"><sp/>b)<sp/>{<sp/></highlight><highlight class="keywordflow">return</highlight><highlight class="normal"><sp/>a<sp/>&gt;<sp/>b;<sp/>}</highlight></codeline>

<codeline><highlight class="normal">);</highlight></codeline>

<codeline><highlight class="normal">cf.<ref refid="classtf_1_1cudaFlow_1a85789ed8a1f47704cf1f1a2b98969444" kindref="member">offload</ref>();</highlight></codeline>

<codeline><highlight class="normal"></highlight></codeline>

<codeline><highlight class="normal">assert(std::is_sorted(vec,<sp/>vec+N,<sp/>[](</highlight><highlight class="keywordtype">int</highlight><highlight class="normal"><sp/>a,<sp/></highlight><highlight class="keywordtype">int</highlight><highlight class="normal"><sp/>b){<sp/></highlight><highlight class="keywordflow">return</highlight><highlight class="normal"><sp/>a<sp/>&gt;<sp/>b;<sp/>}));</highlight></codeline>

</programlisting></para></sect1>

<sect1 id="cudaFlowSort_1cudaFlowSortMiscellaneousItems">

<title>Miscellaneous Items</title>

<para>Parallel sort algorithms are also available in <ref refid="classtf_1_1cudaFlowCapturer" kindref="compound">tf::cudaFlowCapturer</ref> with the same API. </para></sect1>

</detaileddescription>

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