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32 lines
1.2 KiB
TeX
32 lines
1.2 KiB
TeX
%\pagebreak
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\section{Atomic Hint}
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\label{sec:atomic_hint}
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\index{constructs!atomic@\kcode{atomic}}
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\index{atomic construct@\kcode{atomic} construct}
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\index{atomic construct@\kcode{atomic} construct!hint clause@\kcode{hint} clause}
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\index{clauses!hint@\kcode{hint}}
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\index{hint clause@\kcode{hint} clause}
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The atomic \kcode{hint} clause can be used to specify the
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expected access to an atomic operation; thereby providing a hint
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to be used for optimizing the synchronization of the atomic operation.
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In the example below the \kcode{omp_sync_hint_uncontended} constant
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in the \kcode{hint} clause specifies that few threads are expected
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to attempt to perform the atomic operation at the same time.
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This is justified in this case if \ucode{calc_vals} takes considerably
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more time than the atomic operations, and the subsequent time of
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arrival to execute the \kcode{atomic} region is varied about a mean time
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and by times (much) greater than the execution time of the atomic
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operation.
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In the case where the execution time for \ucode{calc_vals} is short
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compared to the atomic operation time, the \kcode{omp_sync_hint_contended}
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hint parameter might be used.
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\cexample[5.0]{atomic}{4}
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\ffreeexample[5.0]{atomic}{4}
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