Does CPython >= 3.10, <=3.12 support a thread-safe increment?
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Mô tả
Documentation
There is no information about it in docs. But the code demonstrates that increment works correctly in multithreading context.
import concurrent.futures
def inc():
global count
for _ in range(1000):
count += 1
for threads_count in range(1, 101):
for _ in range(3):
count = 0
with concurrent.futures.ThreadPoolExecutor(max_workers=threads_count) as exe:
for _ in range(10000):
exe.submit(inc)
print(f"{threads_count=}, {count=}")
import dis
dis.dis(inc)
output
threads=1, count=10000000
threads=1, count=10000000
threads=1, count=10000000
threads=2, count=10000000
threads=2, count=10000000
threads=2, count=10000000
threads=3, count=10000000
threads=3, count=10000000
threads=3, count=10000000
threads=4, count=10000000
threads=4, count=10000000
threads=4, count=10000000
threads=5, count=10000000
threads=5, count=10000000
threads=5, count=10000000
threads=6, count=10000000
threads=6, count=10000000
threads=6, count=10000000
threads=7, count=10000000
threads=7, count=10000000
threads=7, count=10000000
threads=8, count=10000000
threads=8, count=10000000
threads=8, count=10000000
threads=9, count=10000000
threads=9, count=10000000
threads=9, count=10000000
threads=10, count=10000000
threads=10, count=10000000
threads=10, count=10000000
threads=11, count=10000000
threads=11, count=10000000
threads=11, count=10000000
threads=12, count=10000000
threads=12, count=10000000
threads=12, count=10000000
threads=13, count=10000000
threads=13, count=10000000
threads=13, count=10000000
threads=14, count=10000000
threads=14, count=10000000
threads=14, count=10000000
threads=15, count=10000000
threads=15, count=10000000
threads=15, count=10000000
threads=16, count=10000000
threads=16, count=10000000
threads=16, count=10000000
threads=17, count=10000000
threads=17, count=10000000
threads=17, count=10000000
threads=18, count=10000000
threads=18, count=10000000
threads=18, count=10000000
threads=19, count=10000000
threads=19, count=10000000
threads=19, count=10000000
threads=20, count=10000000
threads=20, count=10000000
threads=20, count=10000000
threads=21, count=10000000
threads=21, count=10000000
threads=21, count=10000000
threads=22, count=10000000
threads=22, count=10000000
threads=22, count=10000000
threads=23, count=10000000
threads=23, count=10000000
threads=23, count=10000000
threads=24, count=10000000
threads=24, count=10000000
threads=24, count=10000000
threads=25, count=10000000
threads=25, count=10000000
threads=25, count=10000000
threads=26, count=10000000
threads=26, count=10000000
threads=26, count=10000000
threads=27, count=10000000
threads=27, count=10000000
threads=27, count=10000000
threads=28, count=10000000
threads=28, count=10000000
threads=28, count=10000000
threads=29, count=10000000
threads=29, count=10000000
threads=29, count=10000000
threads=30, count=10000000
threads=30, count=10000000
threads=30, count=10000000
threads=31, count=10000000
threads=31, count=10000000
threads=31, count=10000000
threads=32, count=10000000
threads=32, count=10000000
threads=32, count=10000000
threads=33, count=10000000
threads=33, count=10000000
threads=33, count=10000000
threads=34, count=10000000
threads=34, count=10000000
threads=34, count=10000000
threads=35, count=10000000
threads=35, count=10000000
threads=35, count=10000000
threads=36, count=10000000
threads=36, count=10000000
threads=36, count=10000000
threads=37, count=10000000
threads=37, count=10000000
threads=37, count=10000000
threads=38, count=10000000
threads=38, count=10000000
threads=38, count=10000000
threads=39, count=10000000
threads=39, count=10000000
threads=39, count=10000000
threads=40, count=10000000
threads=40, count=10000000
threads=40, count=10000000
threads=41, count=10000000
threads=41, count=10000000
threads=41, count=10000000
threads=42, count=10000000
threads=42, count=10000000
threads=42, count=10000000
threads=43, count=10000000
threads=43, count=10000000
threads=43, count=10000000
threads=44, count=10000000
threads=44, count=10000000
threads=44, count=10000000
threads=45, count=10000000
threads=45, count=10000000
threads=45, count=10000000
threads=46, count=10000000
threads=46, count=10000000
threads=46, count=10000000
threads=47, count=10000000
threads=47, count=10000000
threads=47, count=10000000
threads=48, count=10000000
threads=48, count=10000000
threads=48, count=10000000
threads=49, count=10000000
threads=49, count=10000000
threads=49, count=10000000
threads=50, count=10000000
threads=50, count=10000000
threads=50, count=10000000
threads=51, count=10000000
threads=51, count=10000000
threads=51, count=10000000
threads=52, count=10000000
threads=52, count=10000000
threads=52, count=10000000
threads=53, count=10000000
threads=53, count=10000000
threads=53, count=10000000
threads=54, count=10000000
threads=54, count=10000000
threads=54, count=10000000
threads=55, count=10000000
threads=55, count=10000000
threads=55, count=10000000
threads=56, count=10000000
threads=56, count=10000000
threads=56, count=10000000
threads=57, count=10000000
threads=57, count=10000000
threads=57, count=10000000
threads=58, count=10000000
threads=58, count=10000000
threads=58, count=10000000
threads=59, count=10000000
threads=59, count=10000000
threads=59, count=10000000
threads=60, count=10000000
threads=60, count=10000000
threads=60, count=10000000
threads=61, count=10000000
threads=61, count=10000000
threads=61, count=10000000
threads=62, count=10000000
threads=62, count=10000000
threads=62, count=10000000
threads=63, count=10000000
threads=63, count=10000000
threads=63, count=10000000
threads=64, count=10000000
threads=64, count=10000000
threads=64, count=10000000
threads=65, count=10000000
threads=65, count=10000000
threads=65, count=10000000
threads=66, count=10000000
threads=66, count=10000000
threads=66, count=10000000
threads=67, count=10000000
threads=67, count=10000000
threads=67, count=10000000
threads=68, count=10000000
threads=68, count=10000000
threads=68, count=10000000
threads=69, count=10000000
threads=69, count=10000000
threads=69, count=10000000
threads=70, count=10000000
threads=70, count=10000000
threads=70, count=10000000
threads=71, count=10000000
threads=71, count=10000000
threads=71, count=10000000
threads=72, count=10000000
threads=72, count=10000000
threads=72, count=10000000
threads=73, count=10000000
threads=73, count=10000000
threads=73, count=10000000
threads=74, count=10000000
threads=74, count=10000000
threads=74, count=10000000
threads=75, count=10000000
threads=75, count=10000000
threads=75, count=10000000
threads=76, count=10000000
threads=76, count=10000000
threads=76, count=10000000
threads=77, count=10000000
threads=77, count=10000000
threads=77, count=10000000
threads=78, count=10000000
threads=78, count=10000000
threads=78, count=10000000
threads=79, count=10000000
threads=79, count=10000000
threads=79, count=10000000
threads=80, count=10000000
threads=80, count=10000000
threads=80, count=10000000
threads=81, count=10000000
threads=81, count=10000000
threads=81, count=10000000
threads=82, count=10000000
threads=82, count=10000000
threads=82, count=10000000
threads=83, count=10000000
threads=83, count=10000000
threads=83, count=10000000
threads=84, count=10000000
threads=84, count=10000000
threads=84, count=10000000
threads=85, count=10000000
threads=85, count=10000000
threads=85, count=10000000
threads=86, count=10000000
threads=86, count=10000000
threads=86, count=10000000
threads=87, count=10000000
threads=87, count=10000000
threads=87, count=10000000
threads=88, count=10000000
threads=88, count=10000000
threads=88, count=10000000
threads=89, count=10000000
threads=89, count=10000000
threads=89, count=10000000
threads=90, count=10000000
threads=90, count=10000000
threads=90, count=10000000
threads=91, count=10000000
threads=91, count=10000000
threads=91, count=10000000
threads=92, count=10000000
threads=92, count=10000000
threads=92, count=10000000
threads=93, count=10000000
threads=93, count=10000000
threads=93, count=10000000
threads=94, count=10000000
threads=94, count=10000000
threads=94, count=10000000
threads=95, count=10000000
threads=95, count=10000000
threads=95, count=10000000
threads=96, count=10000000
threads=96, count=10000000
threads=96, count=10000000
threads=97, count=10000000
threads=97, count=10000000
threads=97, count=10000000
threads=98, count=10000000
threads=98, count=10000000
threads=98, count=10000000
threads=99, count=10000000
threads=99, count=10000000
threads=99, count=10000000
threads=100, count=10000000
threads=100, count=10000000
threads=100, count=10000000
11 0 LOAD_GLOBAL 0 (range)
2 LOAD_CONST 1 (1000)
4 CALL_FUNCTION 1
6 GET_ITER
>> 8 FOR_ITER 6 (to 22)
10 STORE_FAST 0 (_)12 12 LOAD_GLOBAL 1 (count)
14 LOAD_CONST 2 (1)
16 INPLACE_ADD
18 STORE_GLOBAL 1 (count)
20 JUMP_ABSOLUTE 4 (to 8)11 >> 22 LOAD_CONST 0 (None)
24 RETURN_VALUE
Looks like '+=' isn't an atomic op. But stiil I have a correct result.
Can we just use it as a guarantee or it is just an accent coincidence?
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Hướng nghiên cứu
Bắt đầu với ví dụ ThreadPoolExecutor được báo cáo, hàm inc và mã disassembly của nó. Xem lại tài liệu hiện có về threading của Python và tài liệu tham chiếu ngôn ngữ để xác định liệu có bảo đảm nào được áp dụng trên CPython 3.10–3.12 hay không. Công việc được hoàn thành khi hành vi theo từng phiên bản và việc có thể dựa vào += hay không được ghi chép rõ ràng.
Do mô hình lập chỉ mục viết ra từ nội dung của issue.
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