| Re: [eigen] sse transcendental functions |
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- To: eigen@xxxxxxxxxxxxxxxxxxx
- Subject: Re: [eigen] sse transcendental functions
- From: Rohit Garg <rpg.314@xxxxxxxxx>
- Date: Thu, 26 Mar 2009 22:39:36 +0530
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<snip>
>> 1) It could be obvious but what does the DEIGEN_FAST_MATH macro do?
>
> this is explained in the doxy doc, just on top of EIGEN_FAST_MATH,
> basically it allows you to disable some optimizations which might
> degrades the accuracy
Thanks.
>
>> 2) do you feel there is place for fast implementations of such
>> transcendental functions in eigen? I think we should clearly advertise
>> in the documentation that the SSE version is for 'fast-operations' as
>> seems to be the case. BTW, automagically enabling these when the user
>> compiles with -ffast-math would be cool.
>
> well, currently the only problem of accuracy is for sin/cos and single
> precision floating point values out of the range [-8000 : 8000]. In
> such cases, the error is still lower than taking the same value modulo
> 2pi and then call the glibc sin/cos function. So, really, I think, it
> is safe to enable them by default.
Ok.
>
>> 3) any particular reason why the sincos4f from the Julian's sources
>> hasn't made it in yet?
>
> because currently there is no sincos function in eigen.
Well that's exactly what I was asking, sincos function has been
implemented by Julian, then why was it not committed. AFAICS, is it
because the return values are passed by pointer to it?
--
Rohit Garg
http://rpg-314.blogspot.com/
Senior Undergraduate
Department of Physics
Indian Institute of Technology
Bombay