Concurrency Directives

Concurrency Directives start with pipe (|).

Why concurrency ?

Concurrency is a powerful paradigm for two main reasons:

• Performance: It allows unrelated computations to execute simultaneously, optimizing resource utilization.

• Reliability: Processes can be isolated, preventing failures in one process from propagating to others.

U concurrency model

U enables concurrent task at various levels, prioritizing reliability. The levels of concurrency in U are structured as follows:

• User Level: Includes coroutines and lightweight processes such as user-space threads and fibers.
• Host Level: Involves OS threads.
• Hardware Level: Covers interrupts.

Applications relying solely on hardware-level concurrency are typically not considered reliable or portable. They are commonly utilized in specialized environments like embedded systems or high-performance domains such as finance and avionics.

Coroutines

Coroutines encode a state as a recursive function managed by the Scheduler.

:key_value_db : {| 
  # '\|' <=> function to initialize coroutines 
  \| : {
    # '\|/' <=> when Task starts
    \|/ {
      # 'db' is a map shared by coroutines
      :db : [< :name: 'Bob', :age: 20 >]

      # Call <main_loop> with <db>
      main_loop db
    }
  }

  main_loop : {: db
    \|:.. # By default, define all messages: Get, Put
    # '\|?' <=> Match message types: Get or Put
    \|? :|Get, {: key, sender
        sender.|<  @:json db[key]
        \|^ db # Recurse to <main_loop>
    }
    \|? :|Put, {: key, value
        db[key] := value
        sender.|<  @:json :|Ok
        \|^ db # Recurse to <main_loop>
    }
  }
}

or simply:

:key_value_db : {| 
  \|/ [< :name: 'Bob', :age: 20 >], {|?: db
    :-^ Get, :>: key, sender        ::>                    \|< sender, @:json db[key]
    :-^ Put, :>: key, value, sender ::>  db[key] = value;  \|< sender, :|Ok
  }
}

Threads

Most common concurrency functions are available in the target language or OS:

# Start 10 workers
:w : :|.starts 10, :workers ...
# Or
:w : :|.workpool 10


\< w.:|idle-workers
# Prints a list of idle-workers

Asynchronous Expressions

Work in progress...

Interrupts

Work in progress...