on Tue Jun 02 2009, Eric Niebler <eric-AT-boostpro.com> wrote:
Larry Evans wrote:
On 06/01/09 20:26, Eric Niebler wrote:
I'm attaching a simple patch to vector_n_chooser.hpp that replaces some template metaprogramming with preprocessor metaprogramming in the interest of improving compile times. I found this hotspot through profiling, [snip] Eric,
Could you post your benchmark code that showed the improvement in compile speed? I'd like to eventually try it with a variadic template compiler version of fusion vector.
I confess that I'm not actually benchmarking compile speed; rather, I'm benchmarking the number of template instantiations as reported by Steven's template profiler.
Watch out: PP metaprogramming can slow down compilation, too. I had to get Paul Mensonides to help me figure out how to make it efficient in Boost.Python, because what I was doing caused noticeable drag.
I'm profiling TMP-heavy code like some of Proto's and xpressive's tests and cherry-picking the worst offenders. The Fusion vector_n_chooser patch knocked off 100's of template instantiations, for instance.
Better make sure you're actually saving cycles, or you could be obfuscating code for naught. -- Dave Abrahams BoostPro Computing http://www.boostpro.com