116 lines
2.5 KiB
Plaintext
116 lines
2.5 KiB
Plaintext
program dining_philosophers2;
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{$mode objfpc}{$H+}
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uses
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{$IFDEF UNIX}
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cthreads,
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{$ENDIF}
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Classes, SysUtils, SyncObjs;
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const
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PHIL_COUNT = 5;
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LIFESPAN = 7;
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DELAY_RANGE = 950;
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DELAY_LOW = 50;
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PHIL_NAMES: array[1..PHIL_COUNT] of string = ('Aristotle', 'Kant', 'Spinoza', 'Marx', 'Russell');
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type
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TFork = TCriticalSection;
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TPhilosopher = class;
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var
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Forks: array[1..PHIL_COUNT] of TFork;
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Philosophers: array[1..PHIL_COUNT] of TPhilosopher;
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type
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TPhilosopher = class(TThread)
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private
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FName: string;
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FLeftFork, FRightFork: TFork;
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FLefty: Boolean;
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procedure SetLefty(aValue: Boolean);
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procedure SwapForks;
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protected
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procedure Execute; override;
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public
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constructor Create(const aName: string; aForkIdx1, aForkIdx2: Integer);
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property Lefty: Boolean read FLefty write SetLefty;
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end;
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procedure TPhilosopher.SetLefty(aValue: Boolean);
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begin
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if Lefty = aValue then
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exit;
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FLefty := aValue;
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SwapForks;
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end;
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procedure TPhilosopher.SwapForks;
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var
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Fork: TFork;
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begin
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Fork := FLeftFork;
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FLeftFork := FRightFork;
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FRightFork := Fork;
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end;
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procedure TPhilosopher.Execute;
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var
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LfSpan: Integer = LIFESPAN;
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begin
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while LfSpan > 0 do
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begin
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Dec(LfSpan);
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WriteLn(FName, ' sits down at the table');
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FLeftFork.Acquire;
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FRightFork.Acquire;
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WriteLn(FName, ' eating');
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Sleep(Random(DELAY_RANGE) + DELAY_LOW);
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FRightFork.Release;
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FLeftFork.Release;
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WriteLn(FName, ' is full and leaves the table');
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if LfSpan = 0 then
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continue;
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WriteLn(FName, ' thinking');
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Sleep(Random(DELAY_RANGE) + DELAY_LOW);
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WriteLn(FName, ' is hungry');
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end;
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end;
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constructor TPhilosopher.Create(const aName: string; aForkIdx1, aForkIdx2: Integer);
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begin
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inherited Create(True);
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FName := aName;
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FLeftFork := Forks[aForkIdx1];
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FRightFork := Forks[aForkIdx2];
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end;
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procedure DinnerBegin;
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var
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I: Integer;
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Phil: TPhilosopher;
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begin
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for I := 1 to PHIL_COUNT do
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Forks[I] := TFork.Create;
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for I := 1 to PHIL_COUNT do
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Philosophers[I] := TPhilosopher.Create(PHIL_NAMES[I], I, Succ(I mod PHIL_COUNT));
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Philosophers[Succ(Random(5))].Lefty := True;
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for Phil in Philosophers do
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Phil.Start;
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end;
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procedure WaitForDinnerOver;
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var
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Phil: TPhilosopher;
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Fork: TFork;
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begin
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for Phil in Philosophers do
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begin
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Phil.WaitFor;
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Phil.Free;
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end;
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for Fork in Forks do
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Fork.Free;
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end;
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begin
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Randomize;
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DinnerBegin;
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WaitForDinnerOver;
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end.
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