On 07/28/2012 09:31 PM, Bruce Evans wrote:
On Sat, 28 Jul 2012, Stephen Montgomery-Smith wrote:
OK. This clog really seems to work.
x*x + y*y - 1 is computed with a ULP less than 0.8. The rest of the
errors seem to be due to the implementation of log1p. The ULP of the
final answer seems to be never bigger than a little over 2.
I really don't like this version. If we want bignums and slowness, we
can use lib[g]mp or even exec a mostly-interactive calculator (bc for
portability, closed-source bigware for unportability).
This version would have been useful in development to verify that the
doubled or tripled floating point was as exact as intended. Now writing
it in your favourite interactive calculator is easiest, except for the
problem of comparing the results.
I can understand your reticence. I'll let you work some more on clog,
and I will concentrate on the catrig stuff.
But did you see that I messed up my earlier error analysis of log1p(1+x)?
Also, if I had a log1pl, I would have used that.
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