[Numpy-discussion] [Pytables-users] On Numexpr and uint64 type

Francesc Altet faltet@carabos....
Tue Mar 11 05:00:27 CDT 2008

A Tuesday 11 March 2008, Francesc Altet escrigué:
> The thing that makes uint64 so special is that it is the largest
> integer (in current processors) that has a native representation
> (i.e. the processor can operate directly on them, so they can be
> processed very fast), and besides, there is no other (common native)
> type that can fully include all its precision (float64 has a mantissa
> of 53 bits, so this is not enough to represent 64 bits).  So the
> problem is basically what to do when operations with uint64 have
> overflows (or underflows, like for example, dealing with negative
> values).

Mmm, I'm thinking now that there exist a relatively common floating 
point that have a mantissa of 64 bit (at minimum), namely the extended 
precision ploating point [1] (in its 80-bit incarnation, it is an IEEE 
standard).  In modern platforms, this is avalaible as a 'long double', 
and I'm wondering whether it would be useful for Numexpr purposes, but 
seems like it is.

[1] http://en.wikipedia.org/wiki/Extended_precision


>0,0<   Francesc Altet     http://www.carabos.com/
V   V   Cárabos Coop. V.   Enjoy Data

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