Unit test error with numpy rc3

Travis Oliphant oliphant.travis at ieee.org
Thu Oct 26 12:26:14 CDT 2006


Charles R Harris wrote:
>
>
> On 10/26/06, *Travis Oliphant* <oliphant.travis at ieee.org 
> <mailto:oliphant.travis at ieee.org>> wrote:
>
>     Ted Horst wrote:
>     > On Mac OS X tiger (10.4) ppc, long double has increased
>     precision but
>     > the same range as double (it really is 128 bits not 80, btw), so
>     > e**1000 is inf, so this is not really an error.
>     >
>     >
>
>     Thanks for the clarification.   Long-double is not standard across
>     platforms with different platforms choosing to do different things
>     with
>     the extra bytes.    This helps explain one more platform.
>
>     > I'm not sure what is the right thing to do in the test, check for
>     > overflow?  Also, finfo has never worked properly for this type.
>     >
>     In machar.py  is the code that runs to detect all of the
>     parameters.  I
>     think the code should be moved to C as detecting precision on a
>     long-double takes too long.
>
>     The overflow check is a good idea. The test should probably check for
>     overflow and not try to run if it's detected. 
>
>
> How to check overflow? According to the documentation the flag is not 
> set by the hardware. And the precision is variable! Somewhere in the 
> neighborhood of 31 decimal digits, more or less, depending. So I think 
> it is hard to figure out what to do here.

Let's drop the test.    Long-double is available but is not consistent 
across platforms and NumPy has done nothing to try and make it so.  
Thus, let's just let the user beware. 

-Travis


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