A Tuesday 11 March 2008, Charles R Harris escrigué: > On Tue, Mar 11, 2008 at 4:00 AM, Francesc Altet <[EMAIL PROTECTED]> wrote: > > 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. > > Extended precision is iffy. It doesn't work on all platforms and even > when it does the implementation can be strange. I think the normal > double is the only thing you can count on right now.
I see. Oh well, this is kind of a mess and after pondering about this for a long while, we think that, in the end, a good approach would be to simply follow NumPy convention. It has its pros and cons, but it is a well stablished convention anyway, and it is supposed that most of the Numexpr/PyTables users should be used to it. Thanks for the advices, -- >0,0< Francesc Altet http://www.carabos.com/ V V Cárabos Coop. V. Enjoy Data "-" ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Pytables-users mailing list Pytables-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/pytables-users
