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| <title>atomic_init</title> |
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| <body> |
| <div class="refentry"> |
| <a id="id-1"></a> |
| <div class="titlepage"></div> |
| <div xmlns="" class="refnamediv"> |
| <a xmlns="http://www.w3.org/1999/xhtml" id="atomic_init"></a> |
| <h1>atomic_init</h1> |
| <p> |
| Non-atomically initializes an atomic object pointed to by <code xmlns="http://www.w3.org/1999/xhtml" class="varname">obj</code> to a specified value. |
| </p> |
| </div> |
| <div class="refsynopsisdiv"> |
| <h2></h2> |
| <div class="funcsynopsis"> |
| <table xmlns="" border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"> |
| <tr valign="bottom"> |
| <td> |
| <code xmlns="http://www.w3.org/1999/xhtml" class="funcdef"> |
| <a class="link" href="scalarDataTypes.html" target="pagedisplay">void</a> |
| <strong class="fsfunc">atomic_init</strong> |
| (</code> |
| <td>volatile A <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">*obj</var>, </td> |
| </td> |
| </tr> |
| <tr valign="top"> |
| <td> </td> |
| <td>C <var xmlns="http://www.w3.org/1999/xhtml" class="pdparam">value</var><code>)</code></td> |
| </tr> |
| </table> |
| </div> |
| </div> |
| <div class="refsect1"> |
| <a id="description"></a> |
| <h2>Description</h2> |
| <p> |
| The <code class="function">atomic_init</code> function non-atomically |
| initializes the atomic object pointed to by <code class="varname">obj</code> to |
| the value <code class="varname">value</code>. |
| </p> |
| <p> |
| In these operation definitions: |
| </p> |
| <p> |
| </p> |
| <div class="itemizedlist"> |
| <ul class="itemizedlist" style="list-style-type: disc; "> |
| <li class="listitem"> |
| An <code class="code">A</code> refers to one of the atomic types. |
| </li> |
| <li class="listitem"> |
| A <code class="code">C</code> refers to its corresponding non-atomic type. |
| </li> |
| <li class="listitem"> |
| An <code class="code">M</code> refers to the type of the other |
| argument for arithmetic operations. For atomic |
| integer types, <code class="code">M</code> is <code class="code">C</code>. |
| </li> |
| <li class="listitem"> |
| The functions not ending in explicit have the same semantics as the corresponding |
| explicit function with <code class="constant">memory_order_seq_cst</code> |
| for the <code class="code">memory_order</code> argument. |
| </li> |
| <li class="listitem"> |
| The functions that do not have <code class="code">memory_scope</code> |
| argument have the same semantics as |
| the corresponding functions with the <code class="code">memory_scope</code> argument set to |
| <code class="constant">memory_scope_device</code>. |
| </li> |
| </ul> |
| </div> |
| <p> |
| </p> |
| <p> |
| NOTE: With fine-grained system SVM, sharing |
| happens at the granularity of individual loads |
| and stores anywhere in host memory. Memory |
| consistency is always guaranteed at |
| synchronization points, but to obtain finer |
| control over consistency, the OpenCL atomics |
| functions may be used to ensure that the updates |
| to individual data values made by one unit of |
| execution are visible to other execution units. |
| In particular, when a host thread needs fine |
| control over the consistency of memory that is |
| shared with one or more OpenCL devices, it must |
| use atomic and fence operations that are |
| compatible with the C11 atomic operations. |
| </p> |
| <p> |
| We can't require C11 atomics since host programs can |
| be implemented in other programming languages and |
| versions of C or C++, but we do require that the host |
| programs use atomics and that those atomics be compatible |
| with those in C11. |
| </p> |
| <h4><a id="id-1.5.7"></a>Restrictions</h4> |
| <p> |
| All operations on atomic types must be performed using the built-in atomic |
| functions. C11 and C++11 support operators on atomic types. OpenCL C does not |
| support operators with atomic types. Using atomic types with operators should result in a |
| compilation error. |
| </p> |
| <p> |
| The <span class="type">atomic_bool</span>, <span class="type">atomic_char</span>, |
| <span class="type">atomic_uchar</span>, <span class="type">atomic_short</span>, |
| <span class="type">atomic_ushort</span>, <span class="type">atomic_intmax_t</span> |
| and <span class="type">atomic_uintmax_t</span> types are not |
| supported by OpenCL C. |
| </p> |
| <p> |
| OpenCL C requires that the built-in atomic functions on |
| atomic types are lock-free. |
| </p> |
| <p> |
| The <code class="code">_Atomic</code> type specifier and <code class="code">_Atomic</code> |
| type qualifier are not supported by OpenCL C. |
| </p> |
| <p> |
| The behavior of atomic operations where pointer |
| arguments to the atomic functions refers |
| to an atomic type in the private address space is undefined |
| </p> |
| </div> |
| <div class="refsect2"> |
| <a id="example1"></a> |
| <h3> |
| Example |
| </h3> |
| <div class="informaltable"> |
| <table border="0"> |
| <colgroup> |
| <col align="left" class="col1" /> |
| </colgroup> |
| <tbody> |
| <tr> |
| <td align="left"> |
| local atomic_int local_guide; |
| if (get_local_id(0) == 0) |
| atomic_init(&guide, 42); |
| work_group_barrier(CLK_LOCAL_MEM_FENCE); |
| </td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| </div> |
| <div class="refsect1"> |
| <a id="specification"></a> |
| <h2>Specification</h2> |
| <p> |
| <img src="pdficon_small1.gif" /> |
| |
| <a href="https://www.khronos.org/registry/cl/specs/opencl-2.0-openclc.pdf#page=103" target="OpenCL Spec">OpenCL Specification</a> |
| </p> |
| </div> |
| <div class="refsect1"> |
| <a id="seealso"></a> |
| <h2>Also see</h2> |
| <p> |
| <a class="citerefentry" href="atomicFunctions.html"><span class="citerefentry"><span class="refentrytitle">Atomic Functions</span></span></a> |
| </p> |
| </div> |
| <div xmlns="" class="refsect3" lang="en" xml:lang="en"><a xmlns="http://www.w3.org/1999/xhtml" id="Copyright"></a><h4 xmlns="http://www.w3.org/1999/xhtml"></h4><img xmlns="http://www.w3.org/1999/xhtml" src="KhronosLogo.jpg" /><p xmlns="http://www.w3.org/1999/xhtml"></p>Copyright © 2007-2013 The Khronos Group Inc. |
| Permission is hereby granted, free of charge, to any person obtaining a |
| copy of this software and/or associated documentation files (the |
| "Materials"), to deal in the Materials without restriction, including |
| without limitation the rights to use, copy, modify, merge, publish, |
| distribute, sublicense, and/or sell copies of the Materials, and to |
| permit persons to whom the Materials are furnished to do so, subject to |
| the condition that this copyright notice and permission notice shall be included |
| in all copies or substantial portions of the Materials. |
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