On 03/03/11 19:34, Jeremy Maitin-Shepard wrote:
This whole explicitly passing simd<T> in place of T, which seems to be the same thing done in nt2, in order to make use of certain optimizations seems like a poor interface choice. In almost all cases, the user logically cares about a container of T, and wants to work with individual elements, and the library should ensure that SIMD operations are used whenever possible. In particular, the design of the Eigen library, at least in this respect, seems more appropriate. Perhaps I am just misinterpreting the intended semantics of using simd<T>, but if it in fact it results in the logical value_type still being T, then the question is why you would even need to specify simd at all, rather than having it always be used. I also don't see how the optimization can be externalized in the (quite common) case of doing more than element-wise operations. Oh and morevoer, even with the pack interface we have a simd::range adaptor so
std::vector<T> foo(100); transform(simd::range(v), _1 + 3) do the transform using pack internally. Again no need for user care of SIMDization. Bear with me the current lack of doc on this subject. and w/r to eigen, they have the very same low level component of SIMD pack.