KnowCardPython · Concurrency & Parallelism
What does executor.submit(fn, arg) return, and when does the call return control to you?
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More in Concurrency & Parallelism
You submit two tasks; the first is slow, the second fast. You print f1.result() then f2.result(). Which result appears first?
You have a CPU-bound function (heavy number crunching). You run 4 copies across 4 threading.Threads on a 4-core machine. Does it finish ~4x faster?
If the GIL makes threads useless for speeding up CPU work, what ARE threads actually good for in CPython?
You need to share a large mutable dict between parallel workers and have them all update it live. Threads or processes?
What does this print?
```
import threading
class C(threading.Thread):
counter = 0
def run(self):
for _ in range(2000000):
C.counter += 1
a, b = C(), C()
a.start(); b.start()
a.join(); b.join()
print(C.counter)
```
How do you fix the lost-update race on a shared counter incremented by multiple threads?
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