TBB流图的条件执行 [英] TBB flow graph conditional execution
问题描述
有可能控制的执行路径中TBB流图动态地,使用一个节点作为条件变量的输出,以确定另一节点是否应发射
It possible to control execution path in the TBB Flow Graph dynamically, using output of a node as a condition variable to determine whether another node should be launched?
推荐答案
有几种方法可以动态地控制这里的消息在顺其自然::图:
There are a couple ways to dynamically control where messages go in a flow::graph:
您可以明确提出信息到其他节点中的一个节点的身体。请注意, func_body
放消息给 F1
或 F2
,根据其输入值。节点不被 make_edge附()
,因为消息的流动不被图形的拓扑来控制:
You can explicitly put messages to other nodes in the body of a node. Notice that func_body
puts a message to f1
or f2
, depending on the value of its input. The nodes are not attached by make_edge()
, because the flow of messages is not controlled by the topology of the graph:
template<typename T>
struct func_body {
typedef tbb::flow::function_node<T,T> target_node_type;
target_node_type &my_n1;
target_node_type &my_n2;
func_body(target_node_type &node1, target_node_type &node2) : my_n1(node1), my_n2(node2) {}
tbb::flow::continue_msg operator()(const T& in) {
// do some computation
bool send_to_one = in > 0;
if(send_to_one) my_n1.try_put(in);
else my_n2.try_put(in);
return tbb::flow::continue_msg(); // message is discarded if no successor exists
}
};
struct otherbody {
int operator()(const int& in) {
return in;
}
};
int
main() {
tbb::flow::graph g;
tbb::flow::function_node<int,int> f1(g, tbb::flow::unlimited, otherbody());
tbb::flow::function_node<int,int> f2(g, tbb::flow::unlimited, otherbody());
tbb::flow::function_node<int> cn(g, tbb::flow::unlimited, func_body<int>(f1,f2));
}
或者你也可以使用 multifunction_node
(注意类型元组
和的GET
模板中的 TBB ::流量
命名空间,而不是的std ::
作为旧文件。在这种情况下,我们重视)公告 F1
和 F2
到 multifunction_node
。
Or you can use a multifunction_node
(note the types of the tuple
and get
templates are in the tbb::flow
namespace, not std::
as in the old documentation.) Notice in this case we attach f1
and f2
to the output ports of the multifunction_node
.
typedef tbb::flow::multifunction_node<int,tbb::flow::tuple<int,int> > mfnode;
struct mfunc_body {
void operator()(const int& in, mfnode::output_ports_type &op) {
// do some computation
bool send_to_one = in > 0;
if(send_to_one) tbb::flow::get<0>(op).try_put(in);
else tbb::flow::get<1>(op).try_put(in);
}
};
struct otherbody {
int operator()(const int& in) {
return in;
}
};
int
main() {
tbb::flow::graph g;
tbb::flow::function_node<int,int> f1(g, tbb::flow::unlimited, otherbody());
tbb::flow::function_node<int,int> f2(g, tbb::flow::unlimited, otherbody());
mfnode cn(g, tbb::flow::unlimited, mfunc_body());
tbb::flow::make_edge(tbb::flow::output_port<0>(cn), f1);
tbb::flow::make_edge(tbb::flow::output_port<1>(cn), f2);
// ...
}
目前这两种方法在功能上,相同的;每次将产生一个任务来执行 function_nodes的身体
。在未来的 multifunction_node
情况下可以被优化,如果只有一个输出端口 try_put()
来不产卵。
Currently these two methods are functionally-identical; each will spawn a task to execute the body of the function_nodes
. In the future the multifunction_node
case may be optimized to not spawn if only one output port is try_put()
to.
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