Re: IOS floating point performance
Re: IOS floating point performance
- Subject: Re: IOS floating point performance
- From: Conrad Shultz <email@hidden>
- Date: Wed, 07 Aug 2013 14:32:40 -0700
On Aug 7, 2013, at 1:50 PM, Trygve Inda <email@hidden> wrote:
> I have an app that is running slow. I have narrowed it down to several
> functions which are trig-intensive (used to calculate the position of the
> moon at a given moment and more specifically to calculate rise/set times).
>
> To calculate the position and rise/set times for a month on average,
> requires:
>
> 300 trig functions for position
> 24 points in time to find the correct set of three points
> 30 days
> 2 events
>
> Total of 432,000 trig functions (mostly sin and cos)
>
> On my iPad 3, this takes about 3 seconds, and on my desktop (2.3GHz
> Quad-core i7) it is nearly instantaneous.
>
> I am using doubles (not floats).
>
> What can I do to speed this up?
This is somewhat outside my area of expertise, but if your calculations are at least partially independent, and can thus be expressed in terms of vector calculations, then you might take a look at vecLib (part of Accelerate.framework),
https://developer.apple.com/library/ios/#documentation/Performance/Conceptual/vecLib/Reference/reference.html
There’s also a WWDC session from 2011 or 2012 that provides an introduction to Accelerate.framework.
-Conrad
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