[Ada] How do I handle concurrency and multi-threading in Ada?

In Ada, you can handle concurrency and multi-threading using tasking features provided by the language. Ada's tasking model is based on the concept of tasks, which are units of concurrency that can run concurrently and communicate with each other.

Here are the steps to handle concurrency and multi-threading in Ada:

  1. Define tasks: Use the task keyword to define tasks. Tasks can be declared globally or within a block. Each task has its own execution sequence and can run concurrently with other tasks.

  2. Create tasks: Create instances of tasks using the task ... is construct. You can create multiple instances of a task, and each instance will execute independently.

  3. Execute tasks: Tasks can be started using the task_name.start procedure. This starts the execution of the task in a separate thread. You can also use the delay statement to specify a delay before starting a task.

  4. Communicate between tasks: Use Ada's built-in inter-task communication mechanisms to exchange data between tasks. This includes rendezvous, protected objects, and selective wait statements.

    • Rendezvous: Use the entry statement to define a rendezvous point that allows tasks to synchronize and exchange data. Tasks can wait for each other at specified entry points.

    • Protected Objects: Use the protected keyword to define protected objects, which allow safe access to shared data. Protected objects provide mutual exclusion and synchronization mechanisms to ensure data integrity.

    • Selective wait statements: Use the select statement to wait for multiple tasks or entries simultaneously. This allows a task to wait for a specific event from multiple sources.

  5. Synchronize tasks: Use synchronizing mechanisms like semaphores or barriers to coordinate the execution of multiple tasks. Ada provides built-in types like Semaphore and Barrier for this purpose.

  6. Handle task termination: Use the when ... terminate construct to handle task termination. This allows you to perform cleanup operations when a task completes its execution or is terminated.

  7. Handle task exceptions: Use the exception keyword to define exception handlers within tasks. This allows you to handle exceptions that occur during task execution.

  8. Manage task priorities: Use the priority keyword to define task priorities. Higher-priority tasks are executed ahead of lower-priority tasks. You can also use the Ceiling attribute to specify a maximum priority level for protected object operations.

These are the fundamental steps to handle concurrency and multi-threading in Ada. By using Ada's tasking features effectively, you can create reliable and efficient concurrent programs.