[squeak-dev] Re: [ANN] Number comparison, hash, NaN, Point, and other partially ordered sets

Josh Gargus schwa at fastmail.us
Sat Jan 10 10:01:03 UTC 2009

Tim Olson wrote:
> On Jan 8, 2009, at 9:30 AM, Hans-Martin Mosner wrote:
>> AFAIK, the Croquet project needs to have exactly reproducible float
>> arithmetics on all platforms.

Slightly off-topic, but since we have such a knowledgeable crowd...

As noted by John, Croquet uses fdlibm for bit-identical floating point 
math.  Does anyone have a feeling for how difficult (or impossible) it 
will be to achieve identical computation on OpenCL-compliant devices?  
For example, how difficult would it be to port, say, fdlibm, so that 
trancedentals use the exact same code?  Any other show-stoppers that 
might not occur to the naive mind :-)  ?


> Are you using the exact same code on all platforms for  trancendentals 
> and other floating-point functions?  If not, that is going to be the 
> greatest source of different results.  They tend to vary widely on 
> accuracy, since there is no 1/2 ULP accuracy requirement for those 
> functions, unlike for the defined IEEE operations (+,-,*,/,sqrt)
>     -- Tim Olson

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