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I've read TBB flow graph conditional execution and have a slightly different problem.

Is it possible to create a node with multiple inputs and multiple outputs AND to control the execution by a conditional variable? Maybe without ugly casts.

I've attached a simple example how I would like to design the graph. How is the besst way to get it run with TBB flow graph?

  1. start_node sends a start_msg to some_node

  2. if start_msg is empty, some_node sends a continue_msg to end_node, else some_node sends a continue_msg to itself AND a data_msg to end_node

  3. if continue_msg is received by some_node, previous start_msg is checked if it's empty, if so, a continue_msg is send to end_node, else a data_msg is send.

                         +--continue_msg--+
                     |                |
                     +-----+    +-----+
                           |    |
                           |    |   +----data_msg---+
                           v    |  /                 \
start_node --start_msg--> some_node                    end_node
                                   \                  /
                                    +--continue_msg--+

One problem I'm dealing with: I can't say how many good elements are inside of start_msg even is the size is known (let's say start_msg holds a tbb::concurrent_vector<T>. If some_node finds a bad element, it will be ignored and some_node is sending a continue_msg to itself.

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user1587451
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1 Answers1

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It looks like, the source_node can be used in your algorithm. source_node can generate as many messages as you need. So the algorithm can be reworked a bit:

source_node -> ... -> end_node

Why do you need a continue_msg to be sent to the end_node? To mark the last message? Perhaps, you can use a std::pair<T,bool> where the first element is data and the second one is an indication of the last message.

The Body of the source_node finds the valid element in tbb::concurrent_vector<T>, creates a new message make_pair(Data, false) and returns true for each Body invocation. When the last element is extracted from the container it creates make_pair(Data, true) and returns false as an indication of the last element.

Unfortunately, I do not know the original algorithm and my suggestion can be inappropriate. Could you provide more details if it does not suit your needs, please?

Alex
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