Re: IOS floating point performance
Re: IOS floating point performance
- Subject: Re: IOS floating point performance
- From: Thomas Wetmore <email@hidden>
- Date: Thu, 08 Aug 2013 14:17:12 -0400
David,
Those are lightening speeds. So I agree with you wholeheartedly -- there is no sense in working on a custom table-driven approach. The current approach must already be table-based with speeds like that.
Tom Wetmore
On Aug 8, 2013, at 1:26 PM, David Rowland <email@hidden> wrote:
> I wrote an app that calculates the positions of Sun and Moon and other information as well. The heart of the Moon calculation is this. I added a loop around it and called a stopwatch at the beginning and end.
>
> startTime();
> for (int jj = 0; jj<100;++jj)
> {
> //in radians
> double lambda = 3.81040282295402 + 8399.70910754626 * T
> + 0.109781209950443 * sin(adjustValueRadians(2.35619449019234 + 8328.69146829639 * T))
> - 0.022165681500328 * sin(adjustValueRadians(4.5256387504213 - 7214.06294691607 * T))
>
> One hundred times through this loop, on my iPhone 5, took about 0.0028 seconds. Two hundred times took about 0.0056 sec.
>
> I infer that one pass takes about 0.000028 seconds, or 28.0 microseconds.
>
> The functions are probably very carefully written and could not be improved by table lookups, vector libraries, etc. That is barking up the wrong tree.
>
> David
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