Re: [Boost-users] metafunction invocation performance

The solution to this one is provided by Joaquin, in his reply below: I tried compiling your code with MSVC++ 8.0 and it is indeed incredibly slow. After playing a little with the code I realized that MPL views are the culprit here: for some reason it is much faster to fold on a vector-based computation rather than a view: template struct sequence_product : boost::mpl::fold< Sequence1, boost::mpl::vector0<>, boost::mpl::copy< boost::mpl::transform< Sequence2, pair_withboost::mpl::_2 >, boost::mpl::back_inserterboost::mpl::_1 > > {}; This transformation on sequence_product and seq_seqpair_product alone improved the performance tremendously. Additionally I've tried a small optimization: in seq_seqpair_product it is preumable better to fold on Sequence rather than SequencePair, since on average the first is expected to be shorter. Truth be said, I haven't detected any improvement with this, anyway.

Shouldn't there be a dot-product or cross-product of mpl sequences as a general algorithm? and not just 2 sequences but N.

I guess it is the O(n^2) behavior that deterred the author from including the algorithm (much as STL usually does not contain quadratic algorithms). It might be a worthy addition, nonetheless Joaquin --------- Interesting why a joint_view slower than the alternative. This result confirmed then on MSVC8 , gcc4.1, Intel10... regards, /Hicham