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Re: IOS floating point performance
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Re: IOS floating point performance


  • Subject: Re: IOS floating point performance
  • From: Kevin Meaney <email@hidden>
  • Date: Thu, 08 Aug 2013 08:28:12 +0100

I could well be wrong as I'm working from ancient memory but I believe c upgrades floats to doubles to perform calculations and then if result is stored in a float it will chuck away precision at time of assignment to the float.

I would repeat the recommendations of other to try using vlib.

I gather from original question when OP referred to narrowing down to a few functions that this was achieved by profiling.

Kevin

Sent from my iPhone

On 7 Aug 2013, at 21:50, 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?
>
>
>
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  • Follow-Ups:
    • Re: IOS floating point performance
      • From: Roland King <email@hidden>
References: 
 >IOS floating point performance (From: Trygve Inda <email@hidden>)

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