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<h1 class="topictitle1">task_group Class</h1>
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<div class="section"><h2 class="sectiontitle">Description</h2>
<p>A <samp class="codeph">task_group</samp> represents
concurrent execution of a group of tasks. Tasks may be
dynamically added to the group as it is executing. </p>
</div>
<div class="section"><h2 class="sectiontitle">Example with Lambda Expressions</h2>
<pre>#include "tbb/task_group.h"
using namespace tbb;
int Fib(int n) {
if( n<2 ) {
return n;
} else {
int x, y;
task_group g;
g.run([&]{x=Fib(n-1);}); // spawn a task
g.run([&]{y=Fib(n-2);}); // spawn another task
g.wait(); // wait for both tasks to complete
return x+y;
}
}</pre>
<div class="Note"><h3 class="NoteTipHead">
Caution</h3>
<p>Creating a large number of tasks
for a single task_group is not scalable, because
task creation becomes a serial bottleneck. If
creating more than a small number of concurrent
tasks, consider using
<samp class="codeph">parallel_for</samp> or
<samp class="codeph">parallel_invoke</samp> instead, or
structure the spawning as a recursive tree.</p>
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<div class="section"><h2 class="sectiontitle">Members</h2>
<pre>namespace tbb {
class task_group {
public:
task_group();
~task_group();
template<typename Func>
void run( const Func& f );
template<typename Func>
void run( task_handle<Func>& handle );
template<typename Func>
void run_and_wait( const Func& f );
template<typename Func>
void run_and_wait( task_handle<Func>& handle );
task_group_status wait();
bool is_canceling();
void cancel();
}
}</pre>
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<div class="parentlink"><strong>Parent topic:</strong> <a href="../../reference/task_groups.htm">Task Groups</a></div>
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