[squeak-dev] Posits

Tony Garnock-Jones tonyg at leastfixedpoint.com
Mon Nov 14 09:22:34 UTC 2022

Here's a more up-to-date criticism:


Florent de Dinechin, Luc Forget, Jean-Michel Muller, Yohann Uguen. 
Posits: the good, the bad and the ugly. 2018. hal-01959581v2

I still very much like the theory of posits, and their potential for use 
as a storage format. What my reading over the last few days has taught 
me, though, is that I'm not qualified to opine on their uses for 
*computation*! They still seem really promising - it seems like they're 
perhaps *usually* superior to floats for many numerical algorithms, but 
not *always* superior? And you still have to do Proper Numerical 
Analysis, just like with IEEE754. And since the standard posit formats 
have a slightly smaller range of precisely-encoded contiguous integers 
in them, maybe regular floats/doubles are better where you're doing 
something shady like using them in place of a proper integer type 
(*cough cough javascript*)...

On 11/11/22 09:42, Marcel Taeumel wrote:
> Hmm... Patrick just pointed out to me that this critique addresses Unum 
> I. "Posits" are Unum III:
> https://en.wikipedia.org/wiki/Unum_(number_format) 
> <https://en.wikipedia.org/wiki/Unum_(number_format)>
> Hmm...
> Best,
> Marcel
>> Am 11.11.2022 04:34:31 schrieb Craig Latta <craig at blackpagedigital.com>:
>> This critique was interesting also, by William Kahan, the main
>> architect of the IEEE 754-1985 floating-point spec:
>> https://people.eecs.berkeley.edu/~wkahan/UnumSORN.pdf
>> -C
>> --
>> Craig Latta :: research computer scientist ::
>> Black Page Digital :: Berkeley, California ::
>> 663137D7940BF5C0AF :: C1349FB2ADA32C4D5314CE ::

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