On Jan 16, 11:39 pm, Eduardo Lenz <l...@joinville.udesc.br> wrote:
> Hi,
>
> I was using the former processing package with python 2.5 with no problems.
> After switching to python 2.6.1 I am having some problems with the same code.
> The problem seems to be related to the fact that I am using Pool.map
> with a bounded method, since it is inside a class. To clarify a little bit,
> let me show some parts of the code ....
Hello,
> class Pygen3(self)....
I infer this was a typo.
> ....
> ....
> ....
> def calcula(self,indiv):
> ....
> ....
> ....
>
> def evaluate(self):
> ....
> ....
> indiv = range(mult*self.popsize,(mult+1)*self.popsize)
> pool = Pool(processes=nproc)
> results = pool.map(self.calcula,indiv)
I infer the indentation drifted.
> ...
> ...
>
> the error is the following
>
> Exception in thread Thread-1:
> Traceback (most recent call last):
> File "/usr/lib/python2.6/threading.py", line 522, in __bootstrap_inner
> self.run()
> File "/usr/lib/python2.6/threading.py", line 477, in run
> self.__target(*self.__args, **self.__kwargs)
> File "/usr/lib/python2.6/multiprocessing/pool.py", line 225, in
> _handle_tasks
> put(task)
> PicklingError: Can't pickle <type 'instancemethod'>: attribute lookup
> __builtin__.instancemethod failed
>
> Thanks for your help.
Checking on two typos above. I have this working:
from multiprocessing import Process
class C(object):
def m1( self ):
p1 = Process(target=self.m2, args=('bob1',))
p2 = Process(target=self.m2, args=('bob2',))
p1.start()
p2.start()
p1.join()
p2.join()
def m2( self, name ):
print 'hello', name
if __name__ == '__main__':
c= C()
c.m1()
But I get the same error as you with this:
from multiprocessing import Process, Pool
class C(object):
def m1( self ):
arg= range( 10 )
pool= Pool( 5 )
results = pool.map(self.m2,arg)
print results
def m2( self, name ):
print 'hello', name
if __name__ == '__main__':
c= C()
c.m1()
I build a workaround with this:
from multiprocessing import Process, Pool
class C(object):
def m1( self ):
arg= zip( [ self ]* 10, range( 10 ) )
pool= Pool( 5 )
results = pool.map(C_m2,arg)
print results
def m2( self, arg ):
print 'hello', arg
return arg* 2
def C_m2( ar, **kwar ):
return C.m2( *ar, **kwar )
if __name__ == '__main__':
c= C()
c.m1()
Note that you have to explicitly include 'self' as a first parameter
when packing the arguments, and then explicitly unpack it in the
helper function. Also, wrapping 'm2' with '@staticmethod' also fails
with this error:
Exception in thread Thread-1:
Traceback (most recent call last):
File "c:\programs\python26\lib\threading.py", line 522, in
__bootstrap_inner
self.run()
File "c:\programs\python26\lib\threading.py", line 477, in run
self.__target(*self.__args, **self.__kwargs)
File "c:\programs\python26\lib\multiprocessing\pool.py", line 225,
in _handle_tasks
put(task)
PicklingError: Can't pickle <type 'function'>: attribute lookup
__builtin__.function failed
If this works for you, it's possible to make the helper function more
dynamic, by accepting a class name and an attribute name as string
arguments, then retrieving them in the subprocesses.
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