Re: [eigen] sse asin implementation

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I forgot to mention, that "pow" is also definitely useful to vectorize
(think gamma correction on an image).

2009/3/31 Benoit Jacob <jacob.benoit.1@xxxxxxxxx>:
> 2009/3/31 Rohit Garg <rpg.314@xxxxxxxxx>:
>> On Tue, Mar 31, 2009 at 8:18 PM, Benoit Jacob <jacob.benoit.1@xxxxxxxxx> wrote:
>>> What is the motivation for vectorizing asin in Eigen? Do you mean for
>>> people who want a "cwise asin" on a vector? Do you have a use case for
>>> this?
>> Yes. The page on TODO says that transendental functions could be
>> vectorized and since recently sin, cos, log, exp for floats were
>> committed, I thought that eigen could do with other transcendental
>> functions as well. I was planning to implement more transcendentals in
>> the future, but if this is not useful, please tell me.
> Well, the TODO only mentioned very common functions like sin, cos,
> log, exp, for which use cases abound, for example, not long ago on
> this list, Jos Vandenoever had a use case for vectorized cwise sin or
> cos on vectors.
> So vectorizing sin, cos, log, exp, as well as sqrt and perhaps
> inverse_sqrt, is definitely useful.
> But the inverse trigonometric functions like asin, acos, atan, are
> much less commonly used. What's more, they tend to be used most of the
> time on single isolated numbers, not on all coeffs of a vector. So
> it's not clear if a vectorized asin would be used. I would prefer to
> wait for use cases to appear.
> I guess I should have replied sooner but since I didn't take part in
> the earlier discussion I was hesitant.
> Cheers,
> Benoit

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