| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | noah(at)leadboat(dot)com |
| Cc: | Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Peter Eisentraut <peter_e(at)gmx(dot)net>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Proposal: Trigonometric functions in degrees |
| Date: | 2016-01-23 17:08:40 |
| Message-ID: | 28880.1453568920@sss.pgh.pa.us |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
I wrote:
> So the early returns from the buildfarm aren't very good:
> * tern/sungazer isn't getting exactly 0.5 from sind(30).
> The tern/sungazer result implies that this:
> return (sin(x * (M_PI / 180.0)) / sin(30.0 * (M_PI / 180.0))) / 2.0;
> is not producing exactly 0.5, which means that the two sin() calls aren't
> producing identical results, which I suspect is best explained by the
> theory that the compiler is rearranging 30.0 * (M_PI / 180.0) into
> (30.0 * M_PI) / 180.0, and getting a slightly different number that way.
> I think we could fix that by replacing (M_PI / 180.0) by a hard-wired
> constant (computed to say 20 digits or so).
So I pushed that, and tern/sungazer are still failing. Noah, could you
trace through that and see exactly where it's going off the rails?
regards, tom lane
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Peter Geoghegan | 2016-01-23 19:07:00 | Re: PoC: Partial sort |
| Previous Message | Tom Lane | 2016-01-23 15:39:20 | Re: Removing Functionally Dependent GROUP BY Columns |