Amon is right. In my experience, if you want it fast with Marpa::R2, then, if you can, don’t use G1 for lexing, omit unnecessary symbols, streamline your grammar to resemble the desired AST as much as possible, and drop semantic actions altogether, process AST instead.
Examples: https://github.com/rns/Marpa--R2/blob/master/cpan/t/sl_json_ast.t https://github.com/rns/Marpa--R2/blob/master/cpan/t/sl_timeflies.t On Tue, Nov 21, 2017 at 12:52 AM, <[email protected]> wrote: > Hey, all, > > > > I’ve been hoping for some time to replace an existing parser---implemented > using YAPP and a custom lexer---with a parser implemented using Marpa::R2. > > > > After a moderate amount of work, I finally got a working parser. > > > > The grammar is far easier to understand and work with than the old YAPP > parser; because we’re dealing with an indentation based format, I do have > to use a discard event to track indentation depths and emit indentation > tokens and the like. > > > > However, it’s disappointingly slow, taking about twice as long to parse > our full set of files. That was *really* unexpected. > > > > Immediately suspecting my code, I cranked my pathological case through > Devel::NYTProf; imagine my surprise when the top entry in the list of ‘top > 15 subroutines’ was an xsub: Marpa::R2::Thin::V::*stack_step* > <https://groups.google.com/forum/parser-1-line.html#Marpa__R2__Thin__V__stack_step>. > And this wasn’t by a small amount: that routine took 556s out of 590s or > so, and the next most expensive routine is Marpa::R2::Thin::SLR::read at > 12.7s. These completely dominated the total runtime. > > > > While I will try to sanitize my parser and make it postable so people can > perhaps point out problems, I thought I might first just ask: is that sort > of high cost in stack_step generally representative of some sort of problem > in the grammar? Is there some well-known construct that leads to a blow-up > that is easily eliminated, etc.? Is there something I could log or examine > that might shed some light? > > > > Any guidance would be appreciated. > > > > Michael Dorman > > -- > You received this message because you are subscribed to the Google Groups > "marpa parser" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "marpa parser" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
