On 01/31/2012 03:29 PM, mark florisson wrote:
On 30 January 2012 21:03, Lisandro Dalcin<[email protected]> wrote:
I'm testing my code with numpy-dev. They are trying to discourage use
of deprecated APIs, this includes direct access to the ndarray struct.
In order to update your code, you have to pass -DNPY_NO_DEPRECATED_API
to the C compiler (or #define it before including NumPy headers).
However, they have implemented this feature by exposing the ndarray
type with just the Python object header:
https://github.com/numpy/numpy/blob/master/numpy/core/include/numpy/ndarraytypes.h#L695
Obviously, this interact bad with Cython's sizeof check, I'm getting
this runtime warning:
build/lib.linux-x86_64-2.7/petsc4py/lib/__init__.py:64:
RuntimeWarning: numpy.ndarray size changed, may indicate binary
incompatibility
I think there is nothing Cython can do about this (other than
special-casing NumPy to disable this VERY useful warning).
Hmm...but you can still recompile the Cython module and then don't get
the warning, right?
We've already been through at least one such round. People tend to
ignore it, or install warning filters...
If one does want a workaround, we don't have to special case NumPy as
such -- I think it is marginally cleaner to add new obscure syntax which
we only use in numpy.pxd:
ctypedef class numpy.ndarray [object PyArrayObject nosizecheck]:
Or, if anybody bothers, a way to register and automatically run the
functions NumPy provides for checking ABI compatability.
I don't think any changes should be done on the NumPy end.
Weird, shouldn't you be getting an error? Because the size of the
PyArrayObject should be less than what Cython expects.
I've tried the patch below with success, but I'm not convinced...
Does any of you have a suggestion for NumPy folks about how to improve
this?
I'm not sure this should be fixed in NumPy. Their entire point is that
people shouldn't use those attributes directly. I think numpy.pxd
should be fixed, but the problem is that some attributes might be used
in user code (especially shape), and we still want that to work in
nogil mode. As such, I'm not sure what the best way of fixing it is,
without special casing these attributes in the compiler directly.
Maybe Dag will have some thoughts about this.
Well, we should definitely deprecate direct access to the PyArrayObject
fields -- you can either use "cdef int[:]", or, if you use "cdef
np.ndarray[int]", you should use "PyArray_SHAPE".
Problem is that a lot of tutorial material etc. encourages accessing the
fields directly (my fault). But I think it just needs to happen in the
user code.
- Do we just remove the fields from numpy.pxd; or do we put in a
very-special-case in other to give deprecation warnings for a release?
(It'd be a very special transform stage, but only for one release and
then we simply remove both the transform stage and the fields from
numpy.pxd)
- Do we deprecate the whole "cdef np.ndarray[int]" syntax in favour of
"cdef int[:]"? My hunch is against it, as that would render a lot of
code using deprecated features, but it would "solve" the size warning issue.
Dag Sverre
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