group¶

Specifies concurrency group(s) that the task belongs to. Groups limit how many tasks sharing a group can run simultaneously.

Signature¶

template <typename DSL>
static std::set<std::shared_ptr<const GroupDescriptor>> group(threading::ReactionTask& task)

Details¶

Aspect	Detail
When	Task creation (determines concurrency constraints)
Thread	The emitter's thread (the thread that called `emit()`)
Returns	Set of group descriptors, each with a name and concurrency limit
Fusion	Set union — all groups from all words are merged. The task must satisfy all group constraints simultaneously.

Context & Arguments¶

task — the ReactionTask being constructed.

Runs on the emitter's thread during task creation. The scheduler checks all group constraints before dispatching: a task can only start if, for every group it belongs to, the number of currently-running tasks in that group is below the group's concurrency limit.

Example¶

template <typename Group>
struct Sync {
    template <typename DSL>
    static std::set<std::shared_ptr<const GroupDescriptor>> group(threading::ReactionTask& /*task*/) {
        static const auto descriptor = std::make_shared<GroupDescriptor>(
            util::demangle(typeid(Group).name()), 1  // concurrency = 1
        );
        return {descriptor};
    }
};

Built-in Words Using group¶

Sync<G> — creates a group with concurrency limit of 1 (mutual exclusion)
Group<G, N> — creates a group with concurrency limit of N