adding examples of race condition

Author: qianglise

content/example/race.py

@@ -0,0 +1,23 @@
+from concurrent.futures import ThreadPoolExecutor, ProcessPoolExecutor
+from multiprocessing import Value
+
+# define a function to increment the value by 1
+def inc(i):
+    val.value += 1
+
+# using a large number to see the problem
+n = 100000
+
+# create a shared data and initialize it to 0
+val = Value('i', 0)
+with ThreadPoolExecutor(max_workers=4) as pool:
+    pool.map(inc, range(n))
+
+print(val.value)
+
+# create a shared data and initialize it to 0
+val = Value('i', 0)
+with ProcessPoolExecutor(max_workers=4) as pool:
+    pool.map(inc, range(n))
+
+print(val.value)

content/exercise/race_dup.py

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+from concurrent.futures import ProcessPoolExecutor
+from multiprocessing import Array
+
+
+# define a function to increment the value by 1
+def inc(i):
+    ind = mp.current_process().ident % 4
+    arr[ind] += 1
+
+# define a large number
+n = 100000
+
+# create a shared data and initialize it to 0
+arr = Array('i', [0]*4)
+with ProcessPoolExecutor(max_workers=4) as pool:
+    pool.map(inc, range(n))
+
+print(arr[:],sum(arr))

content/exercise/race_lock.py

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+from concurrent.futures import ThreadPoolExecutor, ProcessPoolExecutor
+from multiprocessing import Value, Lock
+
+lock = Lock()
+
+# adding lock
+def inc(i):
+    lock.acquire()
+    val.value += 1
+    lock.release()
+
+
+# define a large number
+n = 100000
+
+# create a shared data and initialize it to 0
+val = Value('i', 0)
+with ThreadPoolExecutor(max_workers=4) as pool:
+    pool.map(inc, range(n))
+
+print(val.value)
+
+# create a shared data and initialize it to 0
+val = Value('i', 0)
+with ProcessPoolExecutor(max_workers=4) as pool:
+    pool.map(inc, range(n))
+
+print(val.value)