[Numpy-discussion] Help with user-defined data type

Neal Becker ndbecker2@gmail....
Sun Feb 17 08:41:57 CST 2008


I'm trying out user-defined data type for numpy, but I'm a bit stuck.  Maybe
someone can spot the problem?

I'm creating a descr like this:

  PyArray_Descr * d = (PyArray_Descr*)(PyObject_New (PyArray_Descr,
&PyArrayDescr_Type));
  d->typeobj = typeptr;
  d->kind = 'O';                // ???
  d->type = 'z';
  d->byteorder = '=';
  d->hasobject = 0;
  d->elsize = sizeof (cmplx_int_t);
  d->alignment = __alignof__ (cmplx_int_t);
  d->subarray = 0;
  d->fields = 0;
  d->names = 0;

  PyArray_ArrFuncs * f = new PyArray_ArrFuncs;
  PyArray_InitArrFuncs (f);
  f->copyswapn = &copyswapn<cmplx_int_t>;
  f->copyswap = &copyswap<cmplx_int_t>;
  f->getitem = &getitem<cmplx_int_t>;
  f->setitem = &setitem<cmplx_int_t>;

  d->f = f;

  incref (typeptr);

Then register:
  PyArray_RegisterDataType (d1);


This seems OK, I get a typenum 256.

But if I try to use it, bad things happen.
This tests creating an array, both from typenum and from descr:

  PyArray_Descr* descr = PyArray_DescrFromType (typenum);

  npy_intp dims[] = {10};

  PyObject * o1 = PyArray_NewFromDescr (&PyArray_Type, descr, 1, dims, 0, 0,
0, 0);

  PyObject * o2 = PyArray_New (&PyArray_Type, 1, dims, descr->type_num, 0,
0, 0, 0, 0);

If I try this for typenum=1, it's fine.  But if I use my typenum=256 I get
>>> a,b = testit (256)
>>> a
python: Objects/typeobject.c:1418: extra_ivars: Assertion `t_size >= b_size'
failed.

Program received signal SIGABRT, Aborted.
0x0000003834c30ec5 in raise () from /lib64/libc.so.6




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