[Numpy-discussion] Solaris Sparc build broken

David Cournapeau david@ar.media.kyoto-u.ac...
Thu Nov 5 01:11:23 CST 2009


David Cournapeau wrote:
> Charles R Harris wrote:
>   
>> On Wed, Nov 4, 2009 at 11:39 PM, David Cournapeau
>> <david@ar.media.kyoto-u.ac.jp <mailto:david@ar.media.kyoto-u.ac.jp>>
>> wrote:
>>
>>     Charles R Harris wrote:
>>     >
>>     >
>>     > On Wed, Nov 4, 2009 at 11:30 PM, David Cournapeau
>>     > <david@ar.media.kyoto-u.ac.jp
>>     <mailto:david@ar.media.kyoto-u.ac.jp>
>>     <mailto:david@ar.media.kyoto-u.ac.jp
>>     <mailto:david@ar.media.kyoto-u.ac.jp>>>
>>     > wrote:
>>     >
>>     >     Charles R Harris wrote:
>>     >
>>     >     >
>>     >     > I don't think it's that bad. Leaving out the ppc and
>>     sticking to
>>     >     ieee,
>>     >     > there is only double precision, extended precision and quad
>>     >     precision
>>     >     > versions of long double and they  are easily determined at
>>     run time.
>>     >
>>     >     How would you determine this at runtime ?
>>     >
>>     >
>>     > Excepting the PPC, just loop adding a number to one, dividing it by
>>     > two at each iteration, and stop when the result is equal to one.
>>
>>     But that's not what I need. I need to know exactly the binary
>>     representation: how many bits in the mantissa/exponent and where, the
>>     exponent, where does subnormals start, the range of NAN
>>     representations,
>>     etc...
>>
>>
>> It tells you how many bits are in the mantissa, and given ieee the
>> rest follows. We only support ieee anyway.
>>     
>
> But is this reliable ? It does not seem to work for long double in
> intel, for example (but seems to work for sparc64, at least using qemu).
>   

Sorry - I forgot 80 bits extended precision format has no implicit bit,
so the relationship between ibeta and number of bits of mantissa is
different in that case.

David


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