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<div class="section">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="boost_compute.tutorial"></a><a class="link" href="tutorial.html" title="Tutorial">Tutorial</a>
</h2></div></div></div>
<div class="toc"><dl class="toc">
<dt><span class="section"><a href="tutorial.html#boost_compute.tutorial.hello_world">Hello World</a></span></dt>
<dt><span class="section"><a href="tutorial.html#boost_compute.tutorial.transferring_data">Transferring
      Data</a></span></dt>
<dt><span class="section"><a href="tutorial.html#boost_compute.tutorial.transforming_data">Transforming
      Data</a></span></dt>
</dl></div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="boost_compute.tutorial.hello_world"></a><a class="link" href="tutorial.html#boost_compute.tutorial.hello_world" title="Hello World">Hello World</a>
</h3></div></div></div>
<p>
        The hello world example gives a simple application that prints the name of
        the default compute device on the system.
      </p>
<p>
        The <code class="computeroutput">boost::compute::system</code>
        class provides access to the OpenCL platforms and devices present on the
        host system.
      </p>
<p>
        Compute devices are represented with the <code class="computeroutput">device</code>
        class.
      </p>
<p>
</p>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">iostream</span><span class="special">&gt;</span>

<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">compute</span><span class="special">/</span><span class="identifier">core</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>

<span class="keyword">namespace</span> <span class="identifier">compute</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">compute</span><span class="special">;</span>

<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span>
<span class="special">{</span>
    <span class="comment">// get the default device</span>
    <span class="identifier">compute</span><span class="special">::</span><span class="identifier">device</span> <span class="identifier">device</span> <span class="special">=</span> <span class="identifier">compute</span><span class="special">::</span><span class="identifier">system</span><span class="special">::</span><span class="identifier">default_device</span><span class="special">();</span>

    <span class="comment">// print the device's name and platform</span>
    <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"hello from "</span> <span class="special">&lt;&lt;</span> <span class="identifier">device</span><span class="special">.</span><span class="identifier">name</span><span class="special">();</span>
    <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">" (platform: "</span> <span class="special">&lt;&lt;</span> <span class="identifier">device</span><span class="special">.</span><span class="identifier">platform</span><span class="special">().</span><span class="identifier">name</span><span class="special">()</span> <span class="special">&lt;&lt;</span> <span class="string">")"</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>

    <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
<span class="special">}</span>
</pre>
<p>
      </p>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="boost_compute.tutorial.transferring_data"></a><a class="link" href="tutorial.html#boost_compute.tutorial.transferring_data" title="Transferring Data">Transferring
      Data</a>
</h3></div></div></div>
<p>
        Before any computation occurs, data must be transferred from the host to
        the compute device. The generic <code class="computeroutput"><a class="link" href="../boost/compute/copy.html" title="Function template copy">copy()</a></code>
        function provides a simple interface for transfering data and the generic
        <code class="computeroutput"><a class="link" href="../boost/compute/vector.html" title="Class template vector">vector&lt;T&gt;</a></code> class
        provides a container for storing data on a compute device.
      </p>
<p>
        The following example shows how to transfer data from an array on the host
        to a <code class="computeroutput"><a class="link" href="../boost/compute/vector.html" title="Class template vector">vector&lt;T&gt;</a></code>
        on the device and then back to a separate <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&gt;</span></code>
        on the host. At the end of the example both <code class="computeroutput"><span class="identifier">host_array</span></code>
        and <code class="computeroutput"><span class="identifier">host_vector</span></code> contain the
        same values which were copied through the memory on the compute device.
      </p>
<p>
</p>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">vector</span><span class="special">&gt;</span>

<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">compute</span><span class="special">/</span><span class="identifier">algorithm</span><span class="special">/</span><span class="identifier">copy</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">compute</span><span class="special">/</span><span class="identifier">container</span><span class="special">/</span><span class="identifier">vector</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>

<span class="keyword">namespace</span> <span class="identifier">compute</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">compute</span><span class="special">;</span>

<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span>
<span class="special">{</span>
    <span class="comment">// get default device and setup context</span>
    <span class="identifier">compute</span><span class="special">::</span><span class="identifier">device</span> <span class="identifier">device</span> <span class="special">=</span> <span class="identifier">compute</span><span class="special">::</span><span class="identifier">system</span><span class="special">::</span><span class="identifier">default_device</span><span class="special">();</span>
    <span class="identifier">compute</span><span class="special">::</span><span class="identifier">context</span> <span class="identifier">context</span><span class="special">(</span><span class="identifier">device</span><span class="special">);</span>
    <span class="identifier">compute</span><span class="special">::</span><span class="identifier">command_queue</span> <span class="identifier">queue</span><span class="special">(</span><span class="identifier">context</span><span class="special">,</span> <span class="identifier">device</span><span class="special">);</span>

    <span class="comment">// create data array on host</span>
    <span class="keyword">int</span> <span class="identifier">host_data</span><span class="special">[]</span> <span class="special">=</span> <span class="special">{</span> <span class="number">1</span><span class="special">,</span> <span class="number">3</span><span class="special">,</span> <span class="number">5</span><span class="special">,</span> <span class="number">7</span><span class="special">,</span> <span class="number">9</span> <span class="special">};</span>

    <span class="comment">// create vector on device</span>
    <span class="identifier">compute</span><span class="special">::</span><span class="identifier">vector</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;</span> <span class="identifier">device_vector</span><span class="special">(</span><span class="number">5</span><span class="special">,</span> <span class="identifier">context</span><span class="special">);</span>

    <span class="comment">// copy from host to device</span>
    <span class="identifier">compute</span><span class="special">::</span><span class="identifier">copy</span><span class="special">(</span>
        <span class="identifier">host_data</span><span class="special">,</span> <span class="identifier">host_data</span> <span class="special">+</span> <span class="number">5</span><span class="special">,</span> <span class="identifier">device_vector</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span> <span class="identifier">queue</span>
    <span class="special">);</span>

    <span class="comment">// create vector on host</span>
    <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special">&lt;</span><span class="keyword">int</span><span class="special">&gt;</span> <span class="identifier">host_vector</span><span class="special">(</span><span class="number">5</span><span class="special">);</span>

    <span class="comment">// copy data back to host</span>
    <span class="identifier">compute</span><span class="special">::</span><span class="identifier">copy</span><span class="special">(</span>
        <span class="identifier">device_vector</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span> <span class="identifier">device_vector</span><span class="special">.</span><span class="identifier">end</span><span class="special">(),</span> <span class="identifier">host_vector</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span> <span class="identifier">queue</span>
    <span class="special">);</span>

    <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
<span class="special">}</span>
</pre>
<p>
      </p>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="boost_compute.tutorial.transforming_data"></a><a class="link" href="tutorial.html#boost_compute.tutorial.transforming_data" title="Transforming Data">Transforming
      Data</a>
</h3></div></div></div>
<p>
        The following example shows how to calculate the square-root of a vector
        of <code class="computeroutput"><span class="keyword">float</span></code>s on a compute device
        using the <code class="computeroutput"><a class="link" href="../boost/compute/transform.html" title="Function transform">transform()</a></code>
        function.
      </p>
<p>
</p>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">vector</span><span class="special">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">algorithm</span><span class="special">&gt;</span>

<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">compute</span><span class="special">/</span><span class="identifier">algorithm</span><span class="special">/</span><span class="identifier">transform</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">compute</span><span class="special">/</span><span class="identifier">container</span><span class="special">/</span><span class="identifier">vector</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
<span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">compute</span><span class="special">/</span><span class="identifier">functional</span><span class="special">/</span><span class="identifier">math</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>

<span class="keyword">namespace</span> <span class="identifier">compute</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">compute</span><span class="special">;</span>

<span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span>
<span class="special">{</span>
    <span class="comment">// get default device and setup context</span>
    <span class="identifier">compute</span><span class="special">::</span><span class="identifier">device</span> <span class="identifier">device</span> <span class="special">=</span> <span class="identifier">compute</span><span class="special">::</span><span class="identifier">system</span><span class="special">::</span><span class="identifier">default_device</span><span class="special">();</span>
    <span class="identifier">compute</span><span class="special">::</span><span class="identifier">context</span> <span class="identifier">context</span><span class="special">(</span><span class="identifier">device</span><span class="special">);</span>
    <span class="identifier">compute</span><span class="special">::</span><span class="identifier">command_queue</span> <span class="identifier">queue</span><span class="special">(</span><span class="identifier">context</span><span class="special">,</span> <span class="identifier">device</span><span class="special">);</span>

    <span class="comment">// generate random data on the host</span>
    <span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special">&lt;</span><span class="keyword">float</span><span class="special">&gt;</span> <span class="identifier">host_vector</span><span class="special">(</span><span class="number">10000</span><span class="special">);</span>
    <span class="identifier">std</span><span class="special">::</span><span class="identifier">generate</span><span class="special">(</span><span class="identifier">host_vector</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span> <span class="identifier">host_vector</span><span class="special">.</span><span class="identifier">end</span><span class="special">(),</span> <span class="identifier">rand</span><span class="special">);</span>

    <span class="comment">// create a vector on the device</span>
    <span class="identifier">compute</span><span class="special">::</span><span class="identifier">vector</span><span class="special">&lt;</span><span class="keyword">float</span><span class="special">&gt;</span> <span class="identifier">device_vector</span><span class="special">(</span><span class="identifier">host_vector</span><span class="special">.</span><span class="identifier">size</span><span class="special">(),</span> <span class="identifier">context</span><span class="special">);</span>

    <span class="comment">// transfer data from the host to the device</span>
    <span class="identifier">compute</span><span class="special">::</span><span class="identifier">copy</span><span class="special">(</span>
        <span class="identifier">host_vector</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span> <span class="identifier">host_vector</span><span class="special">.</span><span class="identifier">end</span><span class="special">(),</span> <span class="identifier">device_vector</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span> <span class="identifier">queue</span>
    <span class="special">);</span>

    <span class="comment">// calculate the square-root of each element in-place</span>
    <span class="identifier">compute</span><span class="special">::</span><span class="identifier">transform</span><span class="special">(</span>
        <span class="identifier">device_vector</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span>
        <span class="identifier">device_vector</span><span class="special">.</span><span class="identifier">end</span><span class="special">(),</span>
        <span class="identifier">device_vector</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span>
        <span class="identifier">compute</span><span class="special">::</span><span class="identifier">sqrt</span><span class="special">&lt;</span><span class="keyword">float</span><span class="special">&gt;(),</span>
        <span class="identifier">queue</span>
    <span class="special">);</span>

    <span class="comment">// copy values back to the host</span>
    <span class="identifier">compute</span><span class="special">::</span><span class="identifier">copy</span><span class="special">(</span>
        <span class="identifier">device_vector</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span> <span class="identifier">device_vector</span><span class="special">.</span><span class="identifier">end</span><span class="special">(),</span> <span class="identifier">host_vector</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span> <span class="identifier">queue</span>
    <span class="special">);</span>

    <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
<span class="special">}</span>
</pre>
<p>
      </p>
</div>
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<td align="right"><div class="copyright-footer">Copyright &#169; 2013, 2014 Kyle Lutz<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>
</div></td>
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