OpenMP and Multithreading - Revision history

Roux at 08:00, 5 September 2011

2011-09-05T08:00:07Z

← Older revision		Revision as of 10:00, 5 September 2011
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			== Tutorials ==

			* [https://computing.llnl.gov/tutorials/openMP From LLNL]

	== C++ ==		== C++ ==

2011-08-29T15:45:43Z

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 === simple parallelization ===
@@ Line 54: / Line 56: @@
+    }
 </source>

2011-04-07T15:09:17Z

simple parallelization

← Older revision		Revision as of 17:09, 7 April 2011
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	</source>		</source>

	* with stl iterators on containers, provided foo() does independent processes ''not efficient'':		* with stl iterators on containers, provided foo() does independent processes (''not efficient''):
	<source lang="cpp">		<source lang="cpp">
	Container cont;		Container cont;

2011-04-07T15:09:02Z

simple parallelization

← Older revision		Revision as of 17:09, 7 April 2011
Line 10:		Line 10:
	</source>		</source>

			* with stl iterators on containers, provided foo() does independent processes ''not efficient'':
	* with stl iterators on containers, provided foo() does independent processes:
	<source lang="cpp">		<source lang="cpp">
	Container cont;		Container cont;

2011-04-07T14:49:33Z

simple parallelization

@@ Line 43: / Line 43: @@
 for (int i = 0; i < a.size(); ++i)
      count += a[i];
 </source>

2011-04-07T13:25:59Z

← Older revision		Revision as of 15:25, 7 April 2011
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	Type count = 0;		Type count = 0;
	Container<Type> a;		Container<Type> a;
	#pragma omp parallel for reduction(+,count)		#pragma omp parallel for reduction(+:count)
	for (int i = 0; i < a.size(); ++i)		for (int i = 0; i < a.size(); ++i)
	count += a[i];		count += a[i];
	</source>		</source>

2011-04-07T13:22:13Z

← Older revision		Revision as of 15:22, 7 April 2011
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	* calculating a sum		* calculating a sum

	<source lang="cpp">		<source lang="cpp">
	~~int~~ count = 0;		Type count = 0;
	Container ~~cont~~;		Container<Type> a;
	#pragma omp parallel for		#pragma omp parallel for
	for (int i = 0; i < ~~cont~~.size(); ++i)		for (int i = 0; i < a.size(); ++i)
	{		{
	#pragma omp atomic		#pragma omp atomic
	count += ~~cont~~[i];		count += a[i];
	}		}
			</source>
			or better
			<source lang="cpp">
			Type count = 0;
			Container<Type> a;
			#pragma omp parallel for reduction(+,count)
			for (int i = 0; i < a.size(); ++i)
			count += a[i];
	</source>		</source>

2011-04-07T10:06:38Z

@@ Line 20: / Line 20: @@
+     {
 #pragma omp single nowait
       foo(It);
+     }
+}
 </source>