Subject: Re: [boost] Boost SIMD beta release
From: Mathias Gaunard (mathias.gaunard_at_[hidden])
Date: 2012-12-20 11:42:08
On 20/12/12 17:35, Tim Blechmann wrote:
>>>> * is it possible to define simd kernels for both packs and scalars e.g.
>>>> to make use of branches in the scalar implementation used in
>>>> preroll/postroll of unrolled loops?
>>>
>>> All operations on pack are also defined on scalar so if you write a
>>> polymorphic template functor, it will work on both. There is a simple
>>> example of
>>> this in the paper.
>>
>> While this works, if you do this you won't be able to use lazy branch
>> evaluation in the scalar version.
>>
>> If you write
>>
>> c = if_else(a != 0, b/a, b);
>>
>> this is equivalent in scalar to
>>
>> c = (a != 0) ? b/a : b;
>>
>> except that in the case above you will always compute the division.
>
> would it be possible to simply provide an overloaded operator() for
> scalar types?
Sure, you can have separate scalar and simd versions, with the caveat
that quite often you'll write nearly the same code twice.