[SciPy-dev] Suppressing of numpy __mul__, __div__ etc
Dmitrey
tmp50@ukr....
Thu Dec 17 01:38:51 CST 2009
От кого: Sebastian Walter <sebastian.walter@gmail.com>
I have also implemented/wrapped various automatic differentiation
tools in python
(http://github.com/b45ch1/algopy , http://github.com/b45ch1/pyadolc,
http://github.com/b45ch1/pycppad if someone is interested)
and I have also come across some numpy glitches and inconsistencies.
However, this particular problem I have not encountered. I'm not sure
I understand the rationale why an expression like numpy.array([1,2] *
oofun(1) should call the oofun.__rmul__ operator.
Hence, I'm a little sceptical about this enhancement.
What is wrong with the following implementation? It works perfectly fine...
--------------- start code snippet -----------------
class oofun:
def __init__(self,x):
self.x = x
def __mul__(self, rhs):
print 'called __mul__'
if isinstance(rhs, oofun):
return oofun(self.x * rhs.x)
else:
return rhs * self
def __rmul__(self, lhs):
print 'called __rmul__'
return oofun(self.x * lhs)
def __str__(self):
return str(self.x)+'a'
def __repr__(self):
return str(self)
------------- end code snippet ----------------
--------- output ----------
basti@shlp:~/Desktop$ python live_demo.py
called __mul__
called __rmul__
called __rmul__
called __rmul__
[2.0a 2.0a 2.0a]
called __rmul__
called __rmul__
called __rmul__
[2.0a 2.0a 2.0a]
But I don't want to get ndarray of N oofuncs, I just want to get single oofunc. At first, evaluating of each oofunc is rather costly, so for N >> 1 I get serious slow down; at second, sometimes my code doesn't work at all - for example, when I create a constraint c = oof1 < oof2 (or lots of other samples). I expect result of a*oof, a/oof etc to be of type oofun while it doesn't (it yields ndarray of oofuns).
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