5 Mar
2013
5 Mar
'13
9:45 a.m.
On 2013/03/04 9:01 PM, Nicolas Rougier wrote:
This made me think of a serious performance limitation of structured dtypes: a structured dtype is always "packed", which may lead to terrible byte alignment for common types. For instance, `dtype([('a', 'u1'), ('b', 'u8')]).itemsize == 9`, meaning that the 8-byte integer is not aligned as an equivalent C-struct's would be, leading to all sorts of horrors at the cache and register level.
Doesn't the "align" kwarg of np.dtype do what you want? In [2]: dt = np.dtype(dict(names=['a', 'b'], formats=['u1', 'u8']), align=True) In [3]: dt.itemsize Out[3]: 16 Eric