[Numpy-discussion] Bug in logaddexp2.reduce

Warren Weckesser warren.weckesser@enthought....
Wed Mar 31 18:37:23 CDT 2010


T J wrote:
> On Wed, Mar 31, 2010 at 1:21 PM, Charles R Harris
> <charlesr.harris@gmail.com> wrote:
>   
>> Looks like roundoff error.
>>
>>     
>
> So this is "expected" behavior?
>
> In [1]: np.logaddexp2(-1.5849625007211563, -53.584962500721154)
> Out[1]: -1.5849625007211561
>
> In [2]: np.logaddexp2(-0.5849625007211563, -53.584962500721154)
> Out[2]: nan
>   

Is any able to reproduce this?  I don't get 'nan' in either 1.4.0 or 
2.0.0.dev8313 (32 bit Mac OSX).  In an earlier email T J reported using 
1.5.0.dev8106.

Warren

> In [3]: np.log2(np.exp2(-0.5849625007211563) + np.exp2(-53.584962500721154))
> Out[3]: -0.58496250072115608
>
> Shouldn't the result at least behave nicely and just return the larger value?
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