c3-m4 dining

c3-m4/main.go

@@ -2,7 +2,9 @@ package main
 
 import (
 	"fmt"
+	"math/rand"
 	"sync"
+	"time"
 )
 
 // ChopS cm
@@ -12,30 +14,62 @@ type ChopS struct {
 
 // Philo cm
 type Philo struct {
+	//6,Each philosopher is numbered, 1 through 5.
+	name            int
 	leftCS, rightCS *ChopS
 }
 
-func (p Philo) eat() {
-	for {
+func (p Philo) eat(semanphore chan int) {
+	// 2.Each philosopher should eat only 3 times (not in an infinite loop as we did in lecture)
+	for i := 0; i < 3; i++ {
 		p.leftCS.Lock()
 		p.rightCS.Lock()
-		fmt.Println("eating")
+		// 7.When a philosopher starts eating
+		fmt.Println("starting to eat ", p.name)
 		p.leftCS.Unlock()
 		p.rightCS.Unlock()
+		// 8.When a philosopher finishes eating
+		fmt.Println("finishing eating ", p.name)
+		<-semanphore // removes an int from semanphore, allowing another to proceed
 	}
 }
 
+// MaxConcurrency Maximum number of gorountine run concurrency
+const MaxConcurrency = 2
+
 func main() {
 	CSticks := make([]*ChopS, 5)
 	for i := 0; i < 5; i++ {
 		CSticks[i] = new(ChopS)
 	}
 	philos := make([]*Philo, 5)
 	for i := 0; i < 5; i++ {
-		philos[i] = &Philo{CSticks[i], CSticks[(i+1)%5]}
+
+		// 3.The philosophers pick up the chopsticks in any order,
+		// not lowest-numbered first (which we did in lecture).
+		// philos[i] = &Philo{CSticks[i], CSticks[(i+1)%5]} // lecture
+		if RandBool() {
+			philos[i] = &Philo{i + 1, CSticks[i], CSticks[(i+1)%5]}
+		}
+		philos[i] = &Philo{i + 1, CSticks[(i+1)%5], CSticks[i]}
+	}
+	semanphore := make(chan int, MaxConcurrency)
+	for {
+
+		for i := 0; i < 5; i++ {
+			// 5.The host allows no more than 2 philosophers to eat concurrently.
+			semanphore <- 1 // will block if there is MaxConccurrency in semanphore
+			// 4.In order to eat, a philosopher must get permission from a host which executes in its own goroutine.
+			go philos[i].eat(semanphore)
+		}
 	}
+}
 
-	for i := 0; i < 5; i++ {
-		go philos[i].eat()
+// RandBool This function returns a random boolean value based on the current time
+func RandBool() bool {
+	rand.Seed(time.Now().UnixNano())
+	if rand.Intn(2) == 1 {
+		return true
 	}
+	return false
 }