Mailman 3 April 2013 - cython-devel

bint and autodoc signatures
by Nikita Nemkin April 16, 2013

April 16, 2013

Hi, Arguments, return values and properties of type 'bint' appear as 'int' in autogenerated signatures. This is very confusing for the end user and logically wrong. (For one thing, bint and int handle input arguments differently: bint accepts pretty much any Python object, while int requries something numeric.) Would it be acceptable to change bint display presentation to 'bool' ? Note: other primitive types (short, int, float, long long etc) don't have this problem, because they are all numeric and coerce to/from Python numerics in an obvious way. Best regards, Nikita Nemkin

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view[0].methodcall() produces invalid C when view is memoryview of extension type
by Matěj Laitl April 15, 2013

April 15, 2013

Hi, following test code produces C code that fails to compile: > cdef class ExtensionType(object): > cdef public int dummy > > def __init__(self, n): > self.dummy = n > > cdef cfoo(self): > print self.dummy > > items = [ExtensionType(1), ExtensionType(2)] > cdef ExtensionType[:] view = np.array(items, dtype=ExtensionType) > view[0].cfoo() with gcc error and relevant C file lines: extension_type_memoryview.c:2604:94: error: ‘PyObject’ has no member named ‘__pyx_vtab’ 2570: PyObject *__pyx_t_1 = NULL; (...) 2601: __pyx_t_1 = (PyObject *) *((struct :__pyx_obj_25extension_type_memoryview_ExtensionType * *) ( /* dim=0 */ : (__pyx_v_25extension_type_memoryview_view.data + __pyx_t_2 * : __pyx_v_25extension_type_memoryview_view.strides[0]) )); 2602: __Pyx_INCREF((PyObject*)__pyx_t_1); 2603: /* __pyx_t_4 allocated */ 2604: __pyx_t_4 = ((struct : __pyx_vtabstruct_25extension_type_memoryview_ExtensionType *)__pyx_t_1 :->__pyx_vtab)->cfoo(__pyx_t_1); if (unlikely(!__pyx_t_4)) {__pyx_filename : = __pyx_f[0]; __pyx_lineno = 69; It seems that generic PyObject* temporary for __pyx_t_1 is used here while typed ExtensionType* temporary should have been used instead (as suggested by excess casting on line 2601). I have the above test-case (and a bit more) prepared as a patch that I'll pull-request one this seemingly trivial bug is fixed in git. Regards, Matěj

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nogil declaration on C++ classes (ticket 805)
by Stefan Behnel April 14, 2013

April 14, 2013

Hi, this patch looks ok to me: http://trac.cython.org/cython_trac/ticket/805 Any objections from the C++ users against including it in 0.19? Stefan

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Re: [Cython] [cython-users] Property + C-level attribute with the same name
by Stefan Behnel April 14, 2013

April 14, 2013

Nikita Nemkin, 13.04.2013 10:07: > The following code exposes a C-level pointer as > an integer property _with the same name_. > ("public" won't work here because type conversion is required.) > > cdef class A: > cdef void* attr > > property attr: > def __get__(self): > return <Py_intptr_t>self.attr > > I have expected a naming error, but it works perfectly. > Can I rely on this behavior or is it accidental? I don't think it's intentional, and it certainly feels like a bug. Although I agree that there might be use in it, it's hard to tell if this is a special case that is useful enough to break the rules. A hugely more general feature would be user defined type conversions, for example, which would make "public" work here and this case could become the compile error that I think it should be. Other opinions? Stefan

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Cython mishandles None in slices
by Bryan O'Sullivan April 13, 2013

April 13, 2013

Here are two lines of valid Python: >>> 'abc'[None:2] 'ab' >>> 'abc'[1:None] 'bc' If I try this in code that I compile with Cython, it throws an exception: TypeError: 'NoneType' object cannot be interpreted as an index

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Bug(?): chained assignments and tuple unpacking
by Alok Singhal April 12, 2013

April 12, 2013

Hi, The following code (also attached as a .pyx file) fails in the current Cython : cdef class test: pass def main(): cdef test a, b, c, d (a, b) = (c, d) = (None, None) When run, I get the following traceback: In [1]: import assign_test In [2]: assign_test.main() Traceback (most recent call last): File "<ipython-input-2-c2f7599d7b34>", line 1, in <module> assign_test.main() File "assign_test.pyx", line 6, in assign_test.main (assign_test.c:669) (a, b) = (c, d) = (None, None) TypeError: Cannot convert NoneType to assign_test.test I am using the latest Cython development version (from github). Also tested with Cython 0.18. $ git rev-parse HEAD e8bd1789905a58d8224e4be5019be401f360aa54 I don't get an error when I change the assignments to either: (a, b) = (None, None) or a = b = None Is this a bug in Cython? I tried doing a git bisect and it seems like commit ea6a71acb5c79afb080855be1cb6ca30d283ec25 is when the above code started failing (It works with the previous commit). Thanks, Alok

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Shared Cython runtime (was: Upcoming cython/numpy breakage with stride checking)
by Nathaniel Smith April 10, 2013

April 10, 2013

On 9 Apr 2013 13:05, "mark florisson" <markflorisson88(a)gmail.com> wrote: > However, the memoryview class is duplicated in every cython module, which means a memoryview object from another module will fail this check. This is a general problem in Cython that could be worked around for memoryviews, but in general the lack of a Cython runtime is a blessing for distribution purposes and a wart for most other purposes. This seems easy to fix - a Cython runtime would be a python module like cython.runtime that Cython modules imported and used, right? You could emulate this perfectly by just checking for such a module in sys.modules at import time, and injecting a copy if none was found. (With some versioning in the name so modules compiled with different versions of Cython could coexist.) This would be much easier than coming up with elaborate object model hacks, since it just uses existing standard python mechanisms... -n

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Constant pointers not working
by Volker Mische April 9, 2013

April 9, 2013

Hi all, I was excited to see that 'const' is finally supported, but constant pointers are not. Here's an example with the corresponding error: Error compiling Cython file: ------------------------------------------------------------ ... cdef extern int foo(const int *const bar) ^ ------------------------------------------------------------ const.pxd:1:37: Expected ')', found 'bar' Cheers, Volker

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Upcoming cython/numpy breakage with stride checking
by Nathaniel Smith April 9, 2013

April 9, 2013

Hi all, If you build current numpy master with NPY_RELAXED_STRIDES_CHECKING=1 python setup.py install then Cython code using ndarrays starts blowing up, e.g.: # foo.pyx def add_one(array): cdef double[::1] a = array a[0] += 1. return array >>> foo.add_one(np.ascontiguousarray(np.arange(10.)[::100])) Traceback (most recent call last): File "<stdin>", line 1, in <module> File "foo.pyx", line 2, in foo.add_one (foo.c:1210) cdef double[::1] a = array ValueError: Buffer and memoryview are not contiguous in the same dimension. The problem (as discussed before) is that Cython has an unnecessarily strict definition of "contiguous", so NPY_RELAXED_STRIDES_CHECKING=1 pretty much breaks all existing compiled Cython modules. Our plan is to make NPY_RELAXED_STRIDES_CHECKING=1 into the default sooner or later, and Cython is a major blocker on this plan. It may become the default as soon as the 1.8 pre-releases (with the expectation that we'll probably have to switch back again before the actual release, but still). References: Previous thread: http://thread.gmane.org/gmane.comp.python.cython.devel/14634 Detailed discussion of the difference between numpy/cython's current definition of "contiguity", and the correct definition: http://thread.gmane.org/gmane.comp.python.cython.devel/14634/focus=14640 The PR implementing NPY_RELAXED_STRIDES_CHECKING: https://github.com/numpy/numpy/pull/3162 Another test case: https://github.com/numpy/numpy/issues/2956 We're hoping that Cython will also switch soon to the more accurate check for contiguity. This shouldn't cause any backwards compatibility problems -- it just means Cython code would make strictly fewer copies, and error out due to lack of contiguity strictly less often, even with older numpys. And it seems like a necessary step for getting this untangled and minimizing user pain. What do you think? -n

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Cython 0.19 beta 1 released
by Stefan Behnel April 7, 2013

April 7, 2013

Hi, I uploaded a first beta release for Cython 0.19. Please give it a try with your code. http://cython.org/release/Cython-0.19b1.tar.gz http://cython.org/release/Cython-0.19b1.zip There were many enhancements and changes regarding performance, usability and Python compatibility, including some very long standing bugs and issues. The changelog is on github: https://github.com/cython/cython/blob/b1f10fa2c1bbb0a076807a9f391204c6a997b… The latest documentation is here: https://sage.math.washington.edu:8091/hudson/job/cython-docs/doclinks/1/ Have fun, Stefan

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