On Wed, Dec 1, 2010 at 3:51 AM, Jeroen Habraken <[email protected]> wrote: > > On 30 November 2010 17:38, Dean Michael Berris <[email protected]> wrote: >> >> I see that the URI code has a lot of rules (>5) which can still be >> reduced into a single rule. Jeroen/Glyn can you try and look at >> reducing the number of rules and consolidate to just one rule just to >> see whether it would help reduce the compile times? >> >> Thanks in advance and I hope to hear what you guys think about trying >> that out. I might do that on my own but getting time lately to work on >> cpp-netlib ironically just got really hard. >> > > There is a best practices documentation addendum here: > http://boost-spirit.com/home/articles/doc-addendum/best-practices/, > which states: > > "Avoid complex rules. Rules with complex definitions hurt the compiler > badly. We’ve seen rules that are more than a hundred lines long and > take a couple of minutes to compile. On some compilers, experience > shows that the compile time is exponential in relation to the RHS > expression length. C++ compilers were not designed to handle such big > expressions and some just couldn’t cope (crashes). It is always best > to break complex rules into more manageable, easier to digest parts. > Doing so also makes the rules more readable." >
Yes, that is true, but there was a mailing list discussion about the cost of doing assignments to rules which basically invokes the Proto evaluator. This kills the compiler because the Proto evaluation is a full-on compiler in itself. Invoking it multiple times is a bigger problem than having it deal with a sufficiently complex rule (in our case it's really just a sequencing of optionals, which shouldn't require too much mumbo-jumbo on the Proto side I imagine). > and I've always understood is that multiple simple rules are > preferable to a single complex rule. However, if I find time I'll look > into combining some rules and testing whether it helps the > compile-time, it shouldn't be to hard. > Yep they were -- especially in the Classic days IIRC. But with Qi and the Proto stuff, the rule assignments get more expensive than the more complex rules if I get my Proto correctly. I'll look forward to your experiments and hopefully we can address some of the compile time concerns as I go head-on into 0.9. Thanks for looking into it Jeroen! -- Dean Michael Berris deanberris.com ------------------------------------------------------------------------------ Increase Visibility of Your 3D Game App & Earn a Chance To Win $500! Tap into the largest installed PC base & get more eyes on your game by optimizing for Intel(R) Graphics Technology. Get started today with the Intel(R) Software Partner Program. Five $500 cash prizes are up for grabs. http://p.sf.net/sfu/intelisp-dev2dev _______________________________________________ Cpp-netlib-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/cpp-netlib-devel
