Created
October 24, 2019 03:37
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Eating philosophers
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package main | |
import ( | |
"fmt" | |
"log" | |
"sync" | |
"time" | |
) | |
const N = 1 | |
var forks [5]*Philosopher | |
type Philosopher int | |
func (p Philosopher) pickLeftFork() { | |
forks[leftFork(p)] = &p | |
log.Println(fmt.Sprintf("[pickLeftFork] forks=%v", forks)) | |
} | |
func (p Philosopher) pickRightFork() { | |
forks[rightFork(p)] = &p | |
log.Println(fmt.Sprintf("[pickRightFork] forks=%v", forks)) | |
} | |
func (p Philosopher) putLeftFork() { | |
forks[leftFork(p)] = nil | |
log.Println(fmt.Sprintf("[putRightFork] forks=%v", forks)) | |
} | |
func (p Philosopher) putRightFork() { | |
forks[rightFork(p)] = nil | |
log.Println(fmt.Sprintf("[putLeftFork] forks=%v", forks)) | |
} | |
func (p Philosopher) eat() { | |
if int(*forks[leftFork(p)]) == int(p) && int(*forks[rightFork(p)]) == int(p) { | |
log.Printf("Eats: %v\n", p) | |
} else { | |
panic(fmt.Sprintf("Forks %d, %d are not taken for philosopher %d, forks=%v", leftFork(p), rightFork(p), p, forks)) | |
} | |
} | |
// ---- | |
var forkMutexes [5]*sync.Mutex | |
var wg sync.WaitGroup | |
func main() { | |
log.Println("Start") | |
for i := 0; i < 5; i++ { | |
forkMutexes[i] = &sync.Mutex{} | |
} | |
for i := 0; i < 5; i++ { | |
wg.Add(N) | |
go func(p Philosopher) { | |
for l := 0; l < N; l++ { | |
p.wantsToEat() | |
wg.Done() | |
time.Sleep(100 * time.Millisecond) | |
} | |
}(Philosopher(i)) | |
} | |
wg.Wait() | |
} | |
func (p Philosopher) wantsToEat() { | |
forkMutexes[leftFork(p)].Lock() | |
p.pickLeftFork() | |
forkMutexes[rightFork(p)].Lock() | |
p.pickRightFork() | |
p.eat() | |
p.putLeftFork() | |
forkMutexes[leftFork(p)].Unlock() | |
p.putRightFork() | |
forkMutexes[rightFork(p)].Unlock() | |
} | |
// ---- | |
func leftFork(philosopher Philosopher) int { | |
if philosopher == 0 { | |
return 4 | |
} | |
return int(philosopher) | |
} | |
func rightFork(philosopher Philosopher) int { | |
if philosopher == 4 { | |
return 0 | |
} | |
return int(philosopher) | |
} |
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