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Re: [PATCH 2/6] Remove slow paths from sin/cos
On Mon, 12 Mar 2018, Wilco Dijkstra wrote:
> Though these patches keep the ULP accuracy across the full range as is,
> we could agree on higher ULP errors for large/huge range reduction cases
> in the future. The main complexity is for certain rare inputs which happen to
> be extremely close to an integer multiple of PI/2, and those few cases mean
> you need significant extra work to guarantee 0.5 ULP error bound on range
> reduction.
I don't think the work for having an error bound not much more than 0.5ulp
on the final result of sin/cos for large arguments is significantly
different from the work for having an error bound of say 3ulp (the
testsuite has a global maximum of 9ulp (16ulp for IBM long double) beyond
which it will not accept errors even if those large errors are listed in
libm-test-ulps files - that bound is simply based on the errors
empirically observed at present, for functions other than Bessel functions
and cpow which are known to have cases with much larger errors).
--
Joseph S. Myers
joseph@codesourcery.com