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{ The Computer Language Shootout
http://shootout.alioth.debian.org
contributed by Marc Weustink
}
program chameneos;
{$mode objfpc}{$h-}
uses
PThreads;
type
TColor = (Blue, Red, Yellow, Faded);
var
waitfirst,
waitsecond : TSemaphore;
first,second : TColor;
MeetingsLeft : Integer;
ThreadInfo : array[0..3] of record
Id: TThreadId;
StartColor: TColor;
Count: Integer;
end;
function Complement(c1,c2:TColor):TColor;
begin
if c2=Faded then
begin
result:=Faded;
exit;
end;
if c1=c2 then
begin
result:=c1;
exit;
end;
case c1 of
Blue :
if c2=Red then
result:=Yellow
else
result:=Red;
Red :
if c2=Blue then
result:=Yellow
else
result:=Blue;
Yellow :
if c2=Blue then
result:=Red
else
result:=Blue;
else
result:=c1;
end;
end;
function OtherCreaturesColor(me:TColor):TColor;
const
firstcall : boolean = true;
begin
result:=Faded;
sem_wait(waitfirst);
if firstCall then
begin
if MeetingsLeft>0 then
begin
first:=me;
firstcall:=false;
sem_post(waitfirst);
sem_wait(waitsecond);
result:=second;
dec(MeetingsLeft);
end;
sem_post(waitfirst);
end
else
begin
firstcall:=true;
second:=me;
result:=first;
sem_post(waitsecond);
end;
end;
function ThreadFunc(AIndex: PtrInt): Pointer; cdecl;
var
Meetings : Integer;
me,other : TColor;
begin
me := ThreadInfo[AIndex].StartColor;
Meetings := 0;
while (me<>Faded) do
begin
other:=OtherCreaturesColor(me);
if other=Faded then
break;
inc(Meetings);
me:=Complement(me,other);
end;
ThreadInfo[AIndex].Count := Meetings;
result:=nil;
end;
const
COLOR: array[0..3] of TColor = (Blue, Red, Yellow, Blue);
var
n: Integer;
Attr: TThreadAttr;
p: Pointer;
begin
Val(paramstr(1), MeetingsLeft, n);
if n <> 0 then exit;
sem_init(waitfirst,0,1);
sem_init(waitsecond,0,0);
pthread_attr_init(Attr);
pthread_attr_setdetachstate(Attr, 0);
pthread_attr_setstacksize(Attr, 1024 * 16);
for n := 0 to 3 do begin
ThreadInfo[n].Count := 0;
ThreadInfo[n].StartColor := COLOR[n];
pthread_create(ThreadInfo[n].Id, Attr, TStartRoutine(@ThreadFunc), Pointer(n));
end;
for n := 0 to 3 do
pthread_join(ThreadInfo[n].Id, p);
WriteLN(ThreadInfo[0].Count + ThreadInfo[1].Count + ThreadInfo[2].Count + ThreadInfo[3].Count);
end.
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