[Numpy-discussion] A little help please?
Neal Becker
ndbecker2@gmail....
Tue Feb 26 05:40:41 CST 2008
My user-defined type project has mostly gone well, but I'm stuck on
mixed-type arithmetic.
I have 2 types: cmplx_int32 and cmplx_int64. I have added basic arithmetic
for those types, and for mix of those arrays and their respective scalars.
But mixed arithmetic only partly works.
In [2]: a
Out[2]: array([(0,0), (1,0), (2,0), (3,0), (4,0), (5,0), (6,0), (7,0),
(8,0), (9,0)], dtype=cmplx_int32)
In [3]: b
Out[3]: array([(0,0), (1,0), (2,0), (3,0), (4,0), (5,0), (6,0), (7,0),
(8,0), (9,0)], dtype=cmplx_int64)
In [4]: a+b
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
/home/nbecker/numpy/<ipython console> in <module>()
TypeError: function not supported for these types, and can't coerce safely
to supported types
In [5]: b+a
Out[5]:
array([(0,0), (2,0), (4,0), (6,0), (8,0), (10,0), (12,0), (14,0), (16,0),
(18,0)], dtype=cmplx_int64)
What I did:
d1 is dtype cmplx_int32, d2 is dtype cmplx_int64.
1. PyArray_RegisterCastFunc (d1, d2->type_num,
&cmplx_to_cmplx<cmplx_int64_t,cmplx_int32_t>);
That registers a conversion from cmplx_int32->cmplx_int64.
(Docs never explain when this conversion is used, BTW)
2. PyArray_RegisterCanCast (d1, d2->type_num, PyArray_NOSCALAR);
3. d1->f->castdict = PyDict_New();
PyObject *key = PyInt_FromLong (d2->type_num);
PyObject *cobj = PyCObject_FromVoidPtr ((void*)(void(*
(void*,void*,npy_intp,void*,void*))&cmplx_to_cmplx<cmplx_int64_t,cmplx_int32_t>,
0);
PyDict_SetItem (d1->f->castdict, key, cobj);
So now add (cmplx_int64, cmplx_int32) is OK, the 2nd arg is converted, but
no attempt is made at radd. Obviously, I don't want to convert 64->32.
Any clues what's missing here?
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