• accelerate application processing times thanks to parallelism Parallelism: several processes are run in parallel instead of sequentially: application speed is improved.
  A simple example Calculate the number of emails sent and received for each email address in the database. If the statistical calculation on an email address takes one second and if the database contains 200 000 email addresses, the calculation takes more than two days.
  To go faster, you have the ability to start a parallel task for each email address found.
  This example is presented in Example: Accelerating the processes.
• improve application responsiveness Line: several long, blocking processes are run in parallel instead of sequentially, so the user doesn't have the impression of being blocked.
  A simple example A Table control displays a list of Contacts whose photo is loaded from an Internet address. For each contact, the application preforms an Internet request (that triggers a slow down).
  In order for the Table control to be filled without being locked, the process for row display starts a parallel task used to start the Internet request and to refresh the GUI if necessary.
  This example is presented in Example: Improving the reactivity of application.

• a variable of type ParallelTask. This type of variable is used to handle a parallel task. This type of variable cannot be used to modify the characteristics of a parallel task.
• functions for managing tasks (ParallelTask*).

Principle

1. Create and run a parallel task.
2. Wait for the execution of the task and retrieve the return value.
3. Manage (if necessary) the sequence of parallel tasks.
4. Manipulate (if necessary) the controls from a parallel task.

Create and run a parallel task

• Simple declaration. The parallel task is described during its execution with ParallelTaskExecute:
  
  // Declares a variable to handle a parallel task
  t is ParallelTask
  // Run and describe the parallel task
  t = ParallelTaskExecute(Proc, ("First parameter", 2))
  
• Declaration and description of the parallel task. Then, the parallel task is run by ParallelTaskExecute.
  

  // Builds a parallel task 
  t is ParallelTask(Proc, ("First parameter", 2))
  // Triggers the execution of parallel task
  ParallelTaskExecute(t)

• the procedure to run.
• the parameters expected by the procedure.
• parallel task execution mode: management of HFSQL contexts and interactions with the main thread.

MyParallelTask keyword

MyParallelTask is used to manage the current parallel task and find out its properties. This allows you to access information about the current parallel task in the code executed by a parallel task. The accessible properties are those of ParallelTask variables:

Property name	Type used	Effect
Canceled	Boolean	True if the task is canceled, False otherwise. This property is read-only.
Completed	Boolean	True if the task is completed, False otherwise. This property is read-only.
Novedad versión 2025 Extra	Variant	Permite almacenar información avanzada sin afectar la ejecución de la aplicación. Puede almacenar valores de cualquier tipo (array, etc.). También es posible agregar miembros a la propiedad Extra. Ejemplo: MyVariable.Extra.Info1 = Value MyVariable.Extra[Info2] = Value2 MyVariable.Extra.Date = DateSys()
Identifier	Integer	Task identifier. This identifier can be used for debugging purpose for example. This property is read-only.
ReturnedValue	Value returned by the task.	Caution: If the task is still in progress, the ReturnedValue property waits for the end of the task If the task is completed without fatal error, the property returns the return values of the procedure of the task. This property is read-only.
Status	Integer constant	Status of the task: tpeCancelled: parallel job is cancelled (function ParallelTaskCancel). tpeRequestedCancellation: a cancellation request has been made on the parallel task (function ParallelTaskRequestCancellation).. tpeWaitExecution the parallel task is waiting to be executed. tpePreviousPreviousTask the parallel task waits for the execution of a previous parallel task. tpeExecutionInProgress the parallel task is currently running. tpeNotScheduled: parallel task is not scheduled. tpeTerminated: parallel task completed. This property is read-only.

Wait for the execution of the task and retrieve the return value

Managing the sequence of parallel tasks

• manage the previous completed task with the MyPreviousParallelTask keyword (ParallelTaskExecuteAfter and ParallelTaskExecuteAfterOne).
• manage previous completed tasks with the MyPreviousParallelTasks keyword (ParallelTaskExecuteAfterAll).

Manipulating the controls from a parallel task

Speed up processing: calculate statistics

• Initial code (before using parallel tasks):
  

  nAddressesInError is int
  
  HourGlass(True)
  ChronoStart()
  // Browses the list of customers
  FOR EACH Customer 
  	// Starts the statistical calculation on the email address
  	IF CalculateStatEmailAddress(Customer.Email, 1) = False THEN
  		nAddressesInError++
  	END
  END
  HourGlass(False)
  LIB_Résultat_1 = StringBuild("Result: %1 addresses in error", nAdressesInError)
  Info("Process completed", DurationToString(ChronoEnd(), "MMm SSs CCC"))

• Code using parallel tasks:
  

  nAddressesInError is int
  arrTasks is array of ParallelTask
  ATask is ParallelTask
  
  HourGlass(True)
  ChronoStart()
  // Browses the list of customers
  FOR EACH Customer 
  	// Starts the statistical calculation on the email address via a parallel task
  	ATask = ParallelTaskExecute(CalculateStatEmailAddress, ...
  			(Customer.Email, 1), ptoLightCopyHFSQLContext)
  	// Stores this task in an array 
  	Add(arrTasks, ATask)
  END
  
  // Waits for the end of task execution
  ParallelTaskWaitAll(arrTasks)
  HourGlass(False)
  
  // Browses the tasks
  FOR EACH ATask OF arrTasks
  	IF ATask..ReturnedValue = False THEN
  		nAddressesInError++
  	END
  END
  LIB_Résultat_2 = StringBuild("Result: %1 addresses in error", nAdressesInError)
  Info("Process completed", DurationToString(ChronoEnd(), "MMm SSs CCC"))

Improving the reactivity of application

• receives the contact identifier in prameter.
• performs the Internet request to get the image.
• retrieves the image.
• calls a function to update the Table control.

• the example 1 updates the GUI via a continuation task.
• the example 2 updates the GUI via a procedure run in the main thread.

Updating the GUI via a continuation task

• Code for displaying a table row:
  
  // If the photo is not filled yet
  IF COL_Photo ~= "" THEN
  // Positions the hourglass image while waiting for the photo to be retrieved from "Internet"
  COL_Photo = IMG_Hourglass
  // Starts retrieving the photo in a parallel task
  MyTaskFindImage is ParallelTask = ParallelTaskExecute(FindImage, ...
  (COL_CustomerNum), ptoLightCopyHFSQLContext)
  // Starts displaying the image in a continuation task
  // that interacts with the interface
  ParallelTaskExecuteAfter(MyTaskFindImage, DisplayImage, ...
  (COL_CustomerNum, ReturnedValuePreviousTask), ptoMainThread)
  END
  
• Procedure code "SearchImage": This procedure retrieves the image.
  

  PROCEDURE FindImage(LOCAL nCustomerID is 8-byte int)
  
  // Retrieve the photo
  Result1 is boolean = HTTPRequest("http://Linkedin.com/photos/id=" + ID)
  IF Result1 = True THEN
  	bufPhoto is Buffer = HTTPGetResult()
  	bufPhoto = fLoadBuffer(fExeDir() + fSep() + "Photos\" + ID + ".jpg")
  END
  
  RETURN bufPhoto

• Code for "DisplayImage" procedure: This procedure displays the image in the.
  
  PROCEDURE DisplayImage(nCustomerID is 8-byte int, sPhotoPath is string)
  // Finds the customer in the table
  nIndex is int = TableSearch("WIN_MENU.TABLE_Customer.COL_CustomerNum", nCustomerID)
  IF nIndex > 0 THEN
  // Displays the customer photo
  WIN_Menu.TABLE_Customer.COL_Photo[nIndex] = sPhotoPath
  END
  

Updating the GUI via a procedure run in the main thread

You also have the ability to indicate to the DisplayImage procedure that it will always be run in the main thread. All you have to do is click the button in the bar of the code editor and check "Run in the main thread".

• Code for displaying a table row:
  
  // If the photo is not filled yet
  IF COL_Photo ~= "" THEN
  // Positions the hourglass image while waiting for the photo to be retrieved from "Internet"
  COL_Photo  = IMG_Hourglass
  // Starts retrieving the photo in a parallel task
  MyTaskFindImage is ParallelTask = ParallelTaskExecute(FindImage, ...
  (COL_CustomerNum), ptoLightCopyHFSQLContext)
  END
  
• Procedure code "SearchImage": This procedure retrieves the image.
  
  PROCÉDURE FindImage(LOCAL nCustomerID is 8-byte int)
  
  // Retrieve the photo
  Result1 is boolean = HTTPRequest("http://Linkedin.com/photos/id=" + ID)
  IF Result1 = True THEN
  bufPhoto is Buffer = HTTPGetResult()
  bufPhoto = fLoadBuffer(fExeDir() + fSep() + "Photos\"+ ID + ".jpg")
  END
  
  // Calls the procedure to display the image
  ExecuteMainThread(DisplayImage, nCustomerID, bufPhoto)
  
• Code for "DisplayImage" procedure: This procedure displays the image in the.
  
  PROCEDURE DisplayImage(nCustomerID is 8-byte int, sPhotoPath is string)
  // Finds the customer in the table
  nIndex is int = TableSearch("WIN_MENU.TABLE_Customer.COL_CustomerNum", nCustomerID)
  IF nIndex > 0 THEN
  // Displays the customer photo
  WIN_Menu.TABLE_Customer.COL_Photo[nIndex] = sPhotoPath
  END