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Overview

Tasks, Modules & Sockets

TODO.

Sequences and Pipelines

TODO.

Module States & Tasks Replicability

In StreamPU, there are modules that are either stateful or stateless. stateful means that it is an instance of a class that inherits from module::Stateful class. On the other hand, a stateless module is necessarily an instance of the module::Stateless class. The module::Stateful and module::Stateless classes both inherit directly from the module::Module class. All stateless modules are clonable. This means that, by default, stateless module tasks are replicable (i.e. they can be replicated within a sequence or pipeline stage to increase the system throughput).

It gets a little bit more complex with stateful modules. By default, a module of this type is non-clonable (i.e. it does not implement the module::Stateful::clone() method). In this case, the tasks that make up the module are, by default, non-replicable. However, the designer of a stateful module can override the module::Stateful::clone() method (basically, the designer has to expresses how to "copy" the module). When it is done, the module becomes clonable and, automatically, the tasks that make up a clonable module become replicable.

Sometimes one may want to force a replicable task to avoid being replicated. For instance, 1) for testing purposes or 2) sometimes certain tasks could be replicated, but in the way they are used it makes no sense and would lead to application malfunction. For this purpose, the public runtime::Task::set_replicability(bool) method gives control to the designer. If the boolean is set to false, then the task is forced to be non-replicable.

Warning

If the input boolean of the runtime::Task::set_replicability(bool) method is set to true and the corresponding module is non-clonable, the method will fail and will throw an exception. In any cases, it will be possible to set the boolean to false (who can do more can do less).

To summarize:

  • stateless module:

    • Always clonable
    • Tasks are by default replicable
    • Tasks can be forced to be non-replicable by the designer

  • stateful module:

    • By default non-clonable
    • Designer can implement the module::Stateful::clone() method to make the module clonable
    • By default, if the module::Stateful::clone() method is not implemented, tasks are non-replicable
    • If the module::Stateful::clone() method is implemented, tasks become replicable and the designer can set the replicability to true or false