[SciPy-Dev] fwrap refactor: Emulating f2py array shape handling?
Dag Sverre Seljebotn
Wed Dec 8 07:26:55 CST 2010
In the ongoing fwrap refactor I'm trying hard to emulate f2py
completely. Still it'd be good to know whether you consider the
behaviour of f2py a feature or a mis-feature. If the latter, it'd be
trivial to, e.g., include a flag that would allow people to experiment
with fwrap vs. f2py behaviour, and change to the former at some point if
the fwrap refactor is pulled upstream.
The question is how functions should deal with arrays of a different
rank than what they expect. Possibilities:
f2py behaviour: Go to very great lengths to convert array shapes. Assume
the function to be called wants a 2D array, then:
- Array of shape (1, 1, 3, 1, 1, 4, 1) is treated as (3, 4) # ignore
- (1, 1, 3, 1, 5, 6) => (3, 30) # flatten trailing dimensions
- (3) -> (3, 1) # pad with 1-length dims on right side
- I think there's more...
fwrap behaviour: Simply raise exception if the rank and dimension does
My opinion: I think f2py is going too far, and would prefer something
that is closer to the simpler broadcasting rules of NumPy ("Explicit is
better than implicit"). Perhaps allow (3,) -> (3, 1), but not the others...
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