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POOpenCL C++ context properties syntax
 

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    <p>I'm trying to learn OpenCL using the C++ bindings. The only thing I haven't understood so far is the following syntax. Trying to create a context based on a device type:</p> <pre><code>cl::Context context(CL_DEVICE_TYPE_CPU, properties); </code></pre> <p>I'm using nvidia's ICD, which as I understand won't let you create a context without defining the platform, so I need the second argument. From the standard, <code>cl_context_properties</code> should be a list of property names, followed by the corresponding values, ended by 0. There's only one <code>cl_context_properties</code> in the standard (table 4.4), which is the property <code>CL_CONTEXT_PLATFORM</code> and has property value of <code>cl_platform_id</code> type. Based on that I thought therefore that this should be OK:</p> <pre><code>cl_context_properties properties[] = { CL_CONTEXT_PLATFORM, platforms[0], 0}; </code></pre> <p>where <code>platforms</code> is my vector of platforms. But it will fail to compile unless instead of <code>platforms[0]</code> I put:</p> <pre><code>(cl_context_properties)(platforms[0])() </code></pre> <p>This is from the example code in the <code>cl.hpp</code> header file.</p> <p>1) It looks like <code>platforms</code> is being cast to type <code>cl_context_properties</code>. Why is this necessary?</p> <p>2) Why is there an extra set of brackets <code>()</code> at the end? </p> <p>Please assume that I'm not a C++ expert (definitely true). I know it's only a small thing but I don't like writing code that I don't understand fully. </p>
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