135 lines
6.3 KiB
HTML
135 lines
6.3 KiB
HTML
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<title>GNU libgomp: CUDA Streams Usage</title>
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<a name="CUDA-Streams-Usage"></a>
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<div class="header">
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<p>
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Next: <a href="OpenACC-Library-Interoperability.html#OpenACC-Library-Interoperability" accesskey="n" rel="next">OpenACC Library Interoperability</a>, Previous: <a href="OpenACC-Environment-Variables.html#OpenACC-Environment-Variables" accesskey="p" rel="prev">OpenACC Environment Variables</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Library-Index.html#Library-Index" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<a name="CUDA-Streams-Usage-1"></a>
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<h2 class="chapter">7 CUDA Streams Usage</h2>
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<p>This applies to the <code>nvptx</code> plugin only.
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</p>
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<p>The library provides elements that perform asynchronous movement of
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data and asynchronous operation of computing constructs. This
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asynchronous functionality is implemented by making use of CUDA
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streams<a name="DOCF1" href="#FOOT1"><sup>1</sup></a>.
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</p>
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<p>The primary means by that the asychronous functionality is accessed
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is through the use of those OpenACC directives which make use of the
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<code>async</code> and <code>wait</code> clauses. When the <code>async</code> clause is
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first used with a directive, it creates a CUDA stream. If an
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<code>async-argument</code> is used with the <code>async</code> clause, then the
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stream is associated with the specified <code>async-argument</code>.
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</p>
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<p>Following the creation of an association between a CUDA stream and the
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<code>async-argument</code> of an <code>async</code> clause, both the <code>wait</code>
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clause and the <code>wait</code> directive can be used. When either the
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clause or directive is used after stream creation, it creates a
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rendezvous point whereby execution waits until all operations
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associated with the <code>async-argument</code>, that is, stream, have
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completed.
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</p>
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<p>Normally, the management of the streams that are created as a result of
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using the <code>async</code> clause, is done without any intervention by the
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caller. This implies the association between the <code>async-argument</code>
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and the CUDA stream will be maintained for the lifetime of the program.
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However, this association can be changed through the use of the library
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function <code>acc_set_cuda_stream</code>. When the function
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<code>acc_set_cuda_stream</code> is called, the CUDA stream that was
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originally associated with the <code>async</code> clause will be destroyed.
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Caution should be taken when changing the association as subsequent
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references to the <code>async-argument</code> refer to a different
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CUDA stream.
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</p>
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<div class="footnote">
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<hr>
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<h4 class="footnotes-heading">Footnotes</h4>
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<h3><a name="FOOT1" href="#DOCF1">(1)</a></h3>
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<p>See "Stream Management" in "CUDA Driver API",
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TRM-06703-001, Version 5.5, for additional information</p>
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</div>
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<hr>
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<div class="header">
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<p>
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Next: <a href="OpenACC-Library-Interoperability.html#OpenACC-Library-Interoperability" accesskey="n" rel="next">OpenACC Library Interoperability</a>, Previous: <a href="OpenACC-Environment-Variables.html#OpenACC-Environment-Variables" accesskey="p" rel="prev">OpenACC Environment Variables</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Library-Index.html#Library-Index" title="Index" rel="index">Index</a>]</p>
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