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# Copyright (C) 2010-2012, Parrot Foundation.
# $Id$
=head1 DESCRIPTION
This file demonstrates cooperative concurrency using continuations on Parrot.
See also http://www.parrot.org/content/threads-are-continuations
=cut
=head1 th_init
First, we create an array to store unscheduled threads in. For simplicity,
this is stored in a global.
=cut
.include 'interpinfo.pasm'
.sub th_init
$P0 = new 'ResizablePMCArray'
set_global 'threads', $P0
.end
=head1 th_create
This is the 'spawn' call. It takes a sub and schedules it to run as a
thread.
=cut
.sub th_create
.param pmc in_sub
$P0 = get_global 'threads'
push $P0, in_sub
.end
=head1 th_resched
This is the 'yield' call. When called from a running thread, it saves the
current point in the computation as a continuation and runs the next thread.
=cut
.sub th_resched
.local pmc cur_th, next_th, ths
ths = get_global 'threads'
# This gets the return continuation for the currently running sub.
# When this continuation is invoked, it will be as if this call
# to th_resched just returned.
cur_th = interpinfo .INTERPINFO_CURRENT_CONT
push ths, cur_th
again:
next_th = shift ths
invokecc next_th
$I0 = ths
if $I0 > 0 goto again
.end
=head1 th_main
This starts up the thread system (after some threads have been scheduled) and makes
sure the program doesn't exit before all the threads have run to completion.
=cut
.sub th_main
.local pmc ths
again1:
ths = get_global 'threads'
$I0 = ths
if $I0 <= 0 goto done
th_resched()
goto again1
done:
.end
=head1 subs and main function
That's it. All we need now is some test threads and a main function to run them.
=cut
.sub sub1
say "sub1: Hallo"
th_resched()
say "sub1: Dance! <(\"< >\")> <(\"<"
th_resched()
say "sub1: Bye"
.end
.sub sub2
say "sub2: Hallo"
th_resched()
say "sub2: Dance! >\")> <(\"< >\")>"
th_resched()
say "sub2: Bye"
.end
.sub sub3
say "sub3: Good morning"
th_resched()
$I0 = 5
$I1 = $I0 + 3
th_resched()
print "sub3: 5 + 3 = "
say $I1
th_resched()
say "sub3: Is leaving."
.end
.sub main :main
th_init()
$P0 = get_global 'sub1'
th_create($P0)
$P0 = get_global 'sub3'
th_create($P0)
$P0 = get_global 'sub2'
th_create($P0)
th_main()
say "All done"
.end
=head1 EXPECTED OUTPUT
The program should (and does) produce this output:
sub1: Hallo
sub3: Good morning
sub2: Hallo
sub1: Dance! <("< >")> <("<
sub2: Dance! >")> <("< >")>
sub1: Bye
sub3: 5 + 3 = 8
sub2: Bye
sub3: Is leaving.
All done
=cut
# Local Variables:
# mode: pir
# fill-column: 100
# End:
# vim: expandtab shiftwidth=4 ft=pir:
|
