Re: [Beowulf] Optimized math routines/transcendentals

2016-04-30 Thread Greg Lindahl
I should have mentioned that when I said that most people/codes don't care about super-accurate range reduction, I was speaking from my various previous lives as a radio astronomer, numerical hydrodynamicist (is that even a word?), and I think it's true for the weather and climate codes that I've w

Re: [Beowulf] Optimized math routines/transcendentals

2016-04-30 Thread Peter St. John
Just one physical oceanographer might need very different precision for a 3-day forecast of currents than for a one-day forecast. I suspect that precision needs will vary even within a lab, much less within a field much less between fields. In the cryptography example, precision is proportional to

Re: [Beowulf] Optimized math routines/transcendentals

2016-04-30 Thread C Bergström
I assume, possibly incorrectly, that scientists know what level of tolerance/accuracy they need. While we can all dream about the futures or past - the present day needs are useful to know. In general a certain field may need A and another field will tolerate B... I guess this is a NaN... if(signa

Re: [Beowulf] Optimized math routines/transcendentals

2016-04-30 Thread Peter St. John
I'm betting the answer to that will be "any" (i.e. "it depends"). In cryptography, we used to think of 128 bits for a PGP key as a lot, but some folks have started using 4096 bits. Of course in exact arithmetic it's much easier to deal with arbitrary precision than in quantitative analysis of meas

Re: [Beowulf] Optimized math routines/transcendentals

2016-04-30 Thread C Bergström
I was hoping for feedback, from scientists, about what level of accuracy their codes or fields of study typically require. Maybe the weekend wasn't the best time to post.. hmm.. On Sun, May 1, 2016 at 1:31 AM, Peter St. John wrote: > A bit off the wall, and not much help for what you are doing no

Re: [Beowulf] Optimized math routines/transcendentals

2016-04-30 Thread Peter St. John
A bit off the wall, and not much help for what you are doing now, but sooner or later we won't be hand-crating ruthlessly optimal code; we'll be training neural nets. You could do this now if you wanted: the objective function is just accurate answers (which you get from sub-optimal but mathematica