On 11/06/11 10:45, David A. Greene wrote:
Vectorizing compilers exist today. They've existing since the 1970's.
I still thinking you're mixing SIMD ISA and vector machine ... As I see it, Vector machine as in http://en.wikipedia.org/wiki/SIMD#Chronology existed since 197x. BUT, what you purposely fake to not understand is that we don't care about this type of machine and focus on this http://en.wikipedia.org/wiki/SIMD#Hardware which exists since 1994 or such and for which the use cases, idioms and techniques are completely different. So yeah, autovectorization on huge CRAY system is done automatically with results I really don't know about and for which i dont care as it is not our target audience but I concede it is maybe good or w/e. Now, strictly speaking on SIMD ISA in x86/PPC familly, no, auto-vectorizing is not that good and still require manual input, functions library and so forth. So in this case, our claims hold and boost.simd has to been has a set of enabling tools for helping people writing generic code able to be vectorized. Learn that Template Meta-Programming as we use it there don't prevent compiler to do stuff afterward our code generation process. They usually do (inlining or loop unrolling etc ...) and we let them do so as they wish cause they fill the gaps we can not access with our library. Did you ever go to the last slides where we have the Range based functions code where no SIMD stuff leak but yet is able to eat up SIMDRange ? I fail to see how this is *not* a correct way of designing code in C++ : - relying on range abstraction + providing a Range with proper properties. And this kind of code is largely sufficent and generic to handle most classical use cases with high level of performances. Dealing with microarchitecture never went that far as manual code goes, and I don't really get your obsession with that.