On Feb 24, 2012, at 7:43 AM, Pierre Haessig wrote: > Hi, > Le 24/02/2012 01:00, Matthew Brett a écrit : >> Right - no proposal to change float64 because it's not ambiguous - it >> is both binary64 IEEE floating point format and 64 bit width. > All right ! Focusing the renaming only on those "extended precision" > float types makes sense. >> The confusion here is for float128 - which is very occasionally IEEE >> binary128 and can be at least two other things (PPC twin double, and >> Intel 80 bit padded to 128 bits). Some of us were also surprised to >> find float96 is the same precision as float128 (being an 80 bit Intel >> padded to 96 bits). >> >> The renaming is an attempt to make it less confusing. Do you agree >> the renaming is less confusing? Do you have another proposal? >> >> Preferring 'longdouble' is precisely to flag up to people that they >> may need to do some more research to find out what exactly that is. >> Which is correct :) > > The renaming scheme you mentionned (float80_96, float80_128, > float128_ieee, float_pair_128 ) is very informative, maybe too much ! > (In this list, I would shorten float128_ieee -> float128 though). > > So in the end, I may concur with you on "longdouble" as a good name for > "extended precision" in the Intel 80 bits sense. (Should "longfloat" be > deprecated ?). > float128 may be kept for ieee definition only, since it looks like the > natural extension of float64. Maybe one day it will be available on our > "standard" machines ? > > Also I just browsed Wikipedia's page [1] to get a bit of background and > I wonder what is the use case of these 80 bits numbers apart from what > is described as "keeping intermediate results" when performing > exponentiation on doubles ?
In AIFF audio files, the sample rate is stored in the Common Chunk as an 80-bit "extended" floating-point number. The field allocated for this is exactly 80 bits wide (i.e., no padding to 96 or 128). The 1989 Apple document defining AIFF can be found at </www-mmsp.ece.mcgill.ca/documents/audioformats/aiff/Docs/AIFF-1.3.pdf> I once wrote my own "save as AIFF" routine and I remember it was a pain to format the 80-bit extended float. Bob Pyle > > Best, > Pierre > > [1] http://en.wikipedia.org/wiki/Extended_precision > > _______________________________________________ > NumPy-Discussion mailing list > NumPy-Discussion@scipy.org > http://mail.scipy.org/mailman/listinfo/numpy-discussion _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
