On Tue, Feb 9, 2016 at 7:06 AM, Daπid <davidmen...@gmail.com> wrote:
> On 8 February 2016 at 18:36, Nathaniel Smith <n...@pobox.com> wrote:
>> I would be highly suspicious that this speed comes at the expense of
>> accuracy... My impression is that there's a lot of room to make
>> speed/accuracy tradeoffs in these functions, and modern glibc's libm has
>> seen a fair amount of scrutiny by people who have access to the same code
>> that openlibm is based off of. But then again, maybe not :-).
>
>
> I did some digging, and I found this:
>
> http://julia-programming-language.2336112.n4.nabble.com/Is-the-accuracy-of-Julia-s-elementary-functions-exp-sin-known-td32736.html
>
> In short: according to their devs, most openlibm functions are
> accurate to less than 1ulp, while GNU libm is rounded to closest
> float.

So GNU libm has max error <= 0.5 ULP, openlibm has <= 1 ULP, and OSX
is (almost always) somewhere in-between.

So, is <= 1 ULP good enough?

Cheers,

Matthew
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