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.
