Hi, On Thu, Mar 8, 2012 at 3:14 PM, Matthew Brett <matthew.br...@gmail.com> wrote: > Hi, > > On Wed, Mar 7, 2012 at 4:08 PM, Matthew Brett <matthew.br...@gmail.com> wrote: >> Hi, >> >> I noticed a casting change running the test suite on our image reader, >> nibabel: >> https://github.com/nipy/nibabel/blob/master/nibabel/tests/test_casting.py >> >> For this script: >> >> <pre> >> import numpy as np >> >> Adata = np.zeros((2,), dtype=np.uint8) >> Bdata = np.zeros((2,), dtype=np.int16) >> Bzero = np.int16(0) >> Bbig = np.int16(256) >> >> print np.__version__ >> print 'Array add', (Adata + Bdata).dtype >> print 'Scalar 0 add', (Adata + Bzero).dtype >> print 'Scalar 256 add', (Adata + Bbig).dtype >> </pre> >> >> 1.4.1 >> Array add int16 >> Scalar 0 add uint8 >> Scalar 256 add uint8 >> >> 1.5.1 >> Array add int16 >> Scalar 0 add uint8 >> Scalar 256 add uint8 >> >> 1.6.1 >> Array add int16 >> Scalar 0 add uint8 >> Scalar 256 add int16 >> >> 1.7.0.dev-aae5b0a >> Array add int16 >> Scalar 0 add uint8 >> Scalar 256 add uint16 >> >> I can understand the uint8 outputs from numpy < 1.6 - the rule being >> not to upcast for scalars. >> >> I can understand the int16 output from 1.6.1 on the basis that the >> value is outside uint8 range and therefore we might prefer a type that >> can handle values from both uint8 and int16. >> >> Was the current change intended? It has the following odd effect: >> >> In [5]: Adata + np.int16(257) >> Out[5]: array([257, 257], dtype=uint16) >> >> In [7]: Adata + np.int16(-257) >> Out[7]: array([-257, -257], dtype=int16) >> >> In [8]: Adata - np.int16(257) >> Out[8]: array([65279, 65279], dtype=uint16) >> >> but I guess you can argue that there are odd effects for other choices too, > > In case it wasn't clear, this, in numpy 1.6.1: > > In [2]: (np.zeros((2,), dtype=np.uint8) + np.int16(257)).dtype > Out[2]: dtype('int16') > > changed to this in current trunk: > > In [2]: (np.zeros((2,), dtype=np.uint8) + np.int16(257)).dtype > Out[2]: dtype('uint16') > > which is different still in previous versions of numpy (e.g. 1.4.1): > > In [2]: (np.zeros((2,), dtype=np.uint8) + np.int16(257)).dtype > Out[2]: dtype('uint8') > > My impression had been that the plan was to avoid changes in the > casting rules if possible. > > Was this change in trunk intentional? If not, I am happy to bisect,
OK - I will assume it was unintentional and make a bug report, Best, Matthew _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
