Threads

• thread definition

  class class_name(threading.Thread) {[override run method] }	Python
  task task_name is [entry entry_name[(parameter ...)]...] end task_name	Ada
  task type task_type_name is [entry entry_name[(parameter ...)]...] end task_type_name	Ada
  class class_name extends Thread {[override run method] }	Java
  thread ...	Pliant
  parallel [threads nb_threads] [mini mini_threshold] [maxi maxi_threshold] [active] ... task parallel_instructions [post sequential_instructions] ...	Pliant
  [NSThread detachNewThreadSelector:mainFunction toTarget:target withObject:obj]	Objective-C

• thread creation

  object t=Thread.Thread(f)	Pike
  set t [thread create {code}]	Tcl
  Thread createThread(...)	Io

• thread object creation

  MyTask : task_type_name;	Ada
  class_name MyThread = new class_name()	Java
  p := [ ... ] newProcess.	Smalltalk
  p := [ ... ] fork.(1)	Smalltalk

• starting / stopping threads

  start() / stop()(2)	Java
  resume / suspend / terminate	Smalltalk
  Tasks are started when created / call Stop entry or "abort task-object-name"	Ada
  thread send $t {script}	Tcl

• passing data directly between threads

  call an entry with parameters	Ada
  call any public method	Java
  common variables are copied at thread creation, in abscence of a "share" statement	Pliant
  use messages, parameters or shared variables(3)	Smalltalk

• terminating thread communication due to a time-out

  select task_entry_call; or delay timeout_limit; end select;

  Ada

• Thread Synchronization

  Defining a Synchronized Shared Resource

  thread::mutex	Tcl
  protected Object_Name is [entry entry_name(Parameter : [in out] is type [...]); procedure procedure_name(Parameter : [in out] is type [...]); function function_name return type; private shared data declaration end Object_Name;	Ada
  synchronize (this){ ... }	Java
  SharedQueue, Semaphore critical: [...], Future, LazyValue	Smalltalk

  Synchronized Writing to a shared resource

  Object_Name.Entry_Name(Parms) Object_Name.Procedure_Name(Parms)	Ada
  Object_Name.SetMethod(Parms)	Java

  Synchronized Reading of a Shared Resource

  Object_Name.Function_Name	Ada
  Object_Name.GetMethod()	Java

  Monitor Syntax

  Objectg_Name.Entry_Name(Parms)

  Ada

• Joining Another Thread

  Suspending a thread until another thread completes

  Call task entry serviced just before task termination	Ada
  OtherThread.join()	Java, Python

  Suspending a Thread Until Another Thread Establishes An Internal State

  Call a task entry on the other thread

  Ada

• Thread Prioritization

  Selecting a Prioritization Model

  pragma Locking_Policy(Ceiling_Locking);

  Ada

  Establishing a base thread priority

  pragma Priority(expression);

  Ada

  Changing Thead Priority

  Set_Priority(Priority_Value);	Ada
  setPriority(newPriority);	Java
  p priority: n	Smalltalk

• Thread-safe sharing of data without synchronization

  Ensuring access is atomic

  pragma Atomic(Object_Name);

  Ada

  Ensuring access is always via a local copy of the shared data

  pragma Volatile(Object_Name);

  Ada

Remarks

• (1) equivalent to newProcess + resume
• (2) "stop" is now deprecated
• (3) a thread is created from a block, which is a closure on the variables as seen by the block