Golang and python thread details and simple examples

Golang and python threads details and simple examples

In GO, 15 threads are started and each thread iterates the global variable 100,000 times, so the predicted result is 15* 100,000 = 1,500,000.

var sum int
var cccc int
var m *sync.Mutex

func Count1(i int, ch chan int) {
  for j := 0; j < 100000; j++ {
   cccc = cccc + 1
  }
  ch <- cccc
}
func main() {
  m = new(sync.Mutex)
  ch := make(chan int, 15)
  for i := 0; i < 15; i++ {
   go Count1(i, ch)
  }
  for i := 0; i < 15; i++ {
   select {
   case msg := <-ch:
     fmt.Println(msg)
   }
  }
}

But the end result, 406,527

It says it needs to be locked.

func Count1(i int, ch chan int) {
  m.Lock()
  for j := 0; j < 100000; j++ {
   cccc = cccc + 1
  }
  ch <- cccc
  m.Unlock()
}

Final output: 1500000

python: same way, no.

count = 0
def sumCount(temp):
  global count
  for i in range(temp):
    count = count + 1
li = []
for i in range(15):
  th = threading.Thread(target=sumCount, args=(1000000,))
  th.start()
  li.append(th)
for i in li:
  i.join()
print(count)

Output result: 3004737

Note also need to be locked:

mutex = threading.Lock()
count = 0
def sumCount(temp):
  global count
  mutex.acquire()
  for i in range(temp):
    count = count + 1
  mutex.release()
li = []
for i in range(15):
  th = threading.Thread(target=sumCount, args=(1000000,))
  th.start()
  li.append(th)
for i in li:
  i.join()
print(count)

The output of 1500000

OK, small column with locks.

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