[Numpy-discussion] Does numpy.bincount support numpy.float128 type weights?

[Sebastian Berg]

Fist off, a word of caution. float128 depends on your system and maps
to whatever longdouble is (IIRC) or may not even exist. So I hope you
don't expect IEEE 128 bit floats, if you are unsure, maybe check
`np.finfo`.

If speed does not matter
```
res = np.zeros(np.max(b), dtype=np.longdouble)
np.add.at(res, b, a)
```
will work, but do not expect it to be fast.

- Sebastian


On Do, 2016-12-01 at 05:54 +0800, Wei, Huayi wrote:
> Hi, There,
> 
> Here is a sample code using `numpy.bincount`
> 
>      import numpy as np
>      a = np.array([1.0, 2.0, 3.0], dtype=np.float128)
>      b = np.array([1, 2, 0], dtype=np.int)
>      c = np.bincount(b, weights=a)
> 
> If run it, I get the following error report:
> 
>      ----> 1 c = np.bincount(b, weights=a)
>      TypeError: Cannot cast array data from dtype('float128') to 
> dtype('float64') according to the rule 'safe'
> 
> Is it a bug of `np.bincount`? Does there exist any similar function 
> which I can use to do the similar thing with numpy.float128 type
> weights?
> 
> Best
> 
> Huayi
> 
> 
> 
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