On Thursday 17 September 2009 06:33:05 Steven D'Aprano wrote: > I have two threads, one running min() and the other running max() over > the same list. I'm getting some mysterious results which I'm having > trouble debugging. Are min() and max() thread-safe, or am I doing > something fundamentally silly by having them walk over the same list > simultaneously? > > My code is as follows. Is there anything obviously wrong with it?
Apart from the plethora of indirection, nothing I can see.
But there is something rotten. Going more basic, look at this:
h...@linuxbox:~/Junk> cat jjj.py
import thread as th
import time
a = range(10000000)
def worker(func,thing):
start_time = time.time()
print "start time is:",start_time
res = func(thing)
print res
end_time = time.time()
print "End at:",end_time,"That took:",end_time-start_time, 'seconds'
t1 = th.start_new_thread(worker,(min,a))
t2 = th.start_new_thread(worker,(max,a))
while True:
time.sleep(1)
h...@linuxbox:~/Junk> python -i jjj.py
start time is: 1253176132.64
0
End at: 1253176133.34 That took: 0.700681209564 seconds
start time is: 1253176133.34
9999999
End at: 1253176134.18 That took: 0.847566127777 seconds
Traceback (most recent call last):
File "jjj.py", line 18, in <module>
time.sleep(1)
KeyboardInterrupt
>>>
No simultaneity.
So when I increase the range to a hundred million to try to force some
concurrency, I get:
h...@linuxbox:~/Junk> python -i jjj.py
Killed
h...@linuxbox:~/Junk>
The behaviour is that it just thrashes for some minutes and then it looks like
the os kills it.
SuSe Linux, dual core Intel with a gig of memory:
Python 2.5.1 (r251:54863, Dec 6 2008, 10:49:39)
[GCC 4.2.1 (SUSE Linux)] on linux2
I enclose the file.
- Hendrik
jjj.py
Description: application/python
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