"{ Package: 'goodies/Parallelism-Futures' }"

"       NAME            Parallelism

	AUTHOR          tph@cs.man.ac.uk

	FUNCTION throttled Futures; lazy eval; explicit pa'l'l procs 

	ST-VERSIONS     stx

	PREREQUISITES    

	CONFLICTS       

	DISTRIBUTION    world

	VERSION         1.1

	DATE    22 Jan 1989

	SUMMARY 

Parallelism contains a number of explicitly parallel constructs,

including a new version of Future, Lazy evaluation, and explicit

parallel processes.  Lots of code in here.  Contains an early

version (read: doesn't work) of a ""throttled"" future mechanism.

New version RSN.(2.2).TPH

claus: I have separated the original Parallelism package into

       individual ones: Lazy, Future, ThrottledFuture and ParallelEvaluation

"!

'From Smalltalk-80, version 2, of April 1, 1983 on 29 March 1987 at 5:13:27 pm'!

!Object methodsFor: 'parallel evaluation'!

touch

	"Simply returns self.  If the receiver is an uncompleted

	 Future or Lazy, this forces complete evaluation."

	^self

! !

Object subclass: #Future

	instanceVariableNames: 'result semaphore '

	classVariableNames: ''

	poolDictionaries: ''

	category: 'Kernel-Processes'

!

Future comment:

'I represent an execution in progress.  Any messages sent to me are delayed until

 execution has completed.'

!

!Future methodsFor: 'synchronising'!

doesNotUnderstand: aMessage

	"Any message to a Future will end up here."

	semaphore wait.     "Wait for evaluation to complete"

			    "(if not already completed)"

	semaphore signal.   "Wake up anything else that might be waiting"

	^result perform: aMessage selector 

		withArguments: aMessage arguments

! !

!Future methodsFor: 'evaluating'!

block: aBlock

	"Execute aBlock in parallel with whatever called me, but

	 ensure that any messages sent to me before execution

	 of the block has terminated are suspended until it has terminated."

	semaphore := Semaphore new.

	[result := aBlock value.  semaphore signal] fork

!

block: aBlock value: aValue

	"Execute aBlock in parallel with whatever called me, but

	 ensure that any messages sent to me before execution

	 of the block has terminated are suspended until it has terminated."

	semaphore := Semaphore new.

	[result := aBlock value: aValue.  semaphore signal] fork

!

block: aBlock value: value1 value: value2

	"Execute aBlock in parallel with whatever called me, but

	 ensure that any messages sent to me before execution

	 of the block has terminated are suspended until it has terminated."

	semaphore := Semaphore new.

	[result := aBlock value: value1 value: value2.

	 semaphore signal] fork

!

block: aBlock value: value1 value: value2 value: value3

	"Execute aBlock in parallel with whatever called me, but

	 ensure that any messages sent to me before execution

	 of the block has terminated are suspended until it has terminated."

	semaphore := Semaphore new.

	[result := aBlock value: value1 value: value2 value: value3.

	 semaphore signal] fork

!

block: aBlock valueWithArguments: anArray

	"Execute aBlock in parallel with whatever called me, but

	 ensure that any messages sent to me before execution

	 of the block has terminated are suspended until it has terminated."

	semaphore := Semaphore new.

	[result := aBlock valueWithArguments: anArray.

	 semaphore signal] fork

! !

!Future class methodsFor: 'class initialization'!

initialize

	"must avoid the checks"

	superclass := nil

	"Future initialize."

! !

Future initialize!

!Block methodsFor: 'parallel evaluation'!

futureValue

	"Fork a synchronised evaluation of myself. Starts the

	 evaluation in parallel immediately."

	^Future new block: self

!

futureValue: aValue

	"Fork a synchronised evaluation of myself. Starts the

	 evaluation in parallel immediately."

	^Future new block: self value: aValue

!

futureValue: aValue value: anotherValue

	"Fork a synchronised evaluation of myself. Starts the

	 evaluation in parallel immediately."

	^Future new block: self value: aValue value: anotherValue

!

futureValue: aValue value: anotherValue value: bValue

	"Fork a synchronised evaluation of myself. Starts the

	 evaluation in parallel immediately."

	^Future new block: self value: aValue value: anotherValue value: bValue

!

futureValueWithArguments: anArray

	"Fork a synchronised evaluation of myself. Starts the

	 evaluation in parallel immediately."

	^Future new block: self valueWithArguments: anArray

! 

parallelAnd: aBlock 

	"Executes the receiver in parallel with aBlock. Once both   

	 have completed, perform a logical AND operation."

	| first second |

	first := self futureValue.

	second := aBlock futureValue.

	^first touch & second touch!

parallelEqv: aBlock 

	"Executes the receiver in parallel with aBlock. Once both   

	 have completed, perform a logical equivalence (exclusive-NOR)

	 operation."

	| first second |

	first := self futureValue.

	second := aBlock futureValue.

	^first touch eqv: second touch!

parallelOr: aBlock 

	"Executes the receiver in parallel with aBlock. Once both   

	 have completed, perform a logical OR operation."

	| first second |

	first := self futureValue.

	second := aBlock futureValue.

	^first touch | second touch!

parallelPerform: aSymbol with: aBlock 

	"Executes the receiver in parallel with aBlock. Once both  

	 have completed, perform the operation given by aSymbol."

	| first second |

	first := self futureValue.

	second := aBlock futureValue.

	^first touch perform: aSymbol with: second touch!

parallelXor: aBlock 

	"Executes the receiver in parallel with aBlock. Once both   

	 have completed, perform a logical equivalence (exclusive-NOR)

	 operation."

	| first second |

	first := self futureValue.

	second := aBlock futureValue.

	^first touch xor: second touch

! !

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"!