On 17/04/07, Lou Pecora <[EMAIL PROTECTED]> wrote:
I get what you are saying, but I'm not even at the
Stupidly Easy Parallel level, yet. Eventually.
Well, it's hardly wonderful, but I wrote a little package to make idioms like:
d = {}
def work(f):
d[f] = sum(exp(2.j*pi*f*times))
foreach(work,freqs,threads=3)
work fine.
Of course you need to make sure your threads don't accidentally
trample all over each other, but otherwise it's an easy way to get a
factor-of-two speedup.
Anne
import sys
import time
import threading
# FIXME: propagate exceptions
def foreach(f,l,threads=3):
"""
Apply f to each element of l, in parallel
"""
if threads>1:
iteratorlock = threading.Lock()
i = l.__iter__()
exceptions = []
def runall():
while True:
iteratorlock.acquire()
try:
try:
if exceptions:
return
v = i.next()
finally:
iteratorlock.release()
except StopIteration:
return
try:
f(v)
except:
e = sys.exc_info()
iteratorlock.acquire()
try:
exceptions.append(e)
finally:
iteratorlock.release()
threadlist = [threading.Thread(target=runall) for j in xrange(threads)]
for t in threadlist:
t.start()
for t in threadlist:
t.join()
if exceptions:
a, b, c = exceptions[0]
raise a, b, c
else:
for v in l:
f(v)
if __name__=='__main__':
def f(x):
print x
time.sleep(0.5)
foreach(f,range(10))
def g(x):
time.sleep(0.5)
print x
raise ValueError, x
time.sleep(0.5)
foreach(g,range(10))
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