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chromatic (983)

chromatic
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http://wgz.org/chromatic/

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Thursday April 24, 2008
04:16 PM

Perl 6 Design Minutes for 23 April 2008

[ #36241 ]

The Perl 6 design team met by phone on 23 April 2008. Larry, Allison, Patrick, Jerry, Will, Jesse, Nicholas, and chromatic attended.

Jerry:

  • we're in a period where everyone's trying to break Parrot
  • they're adding new features and accidentally breaking thing
  • but they're fixing it
  • it's a good part of the cycle
  • people fix it
  • we don't have a build farm, so we can't test everywhere before committing to trunk

Patrick:

  • I thought that was the point of the release cycle

Jerry:

  • some people have suggested that we always keep trunk building and passing tests
  • but we don't have the means to do that
  • especially when we're playing with config
  • moving on, the big news is that TPF has six slots in Google's Summer of Code
  • one of them is fleshing out the Perl 6 test suite
  • we've needed someone to spearhead that
  • having a funded new contributor is wonderful
  • two Parrot-related projects
  • one is generating NCI stubs
  • Kevin Tew, a long-time contributor
  • the other is the incremental GC specified in the PDD
  • that's Andrew Whitworth
  • there's also an ASF project for integrating the GC from Apache Harmony into Parrot
  • they've wanted to release it as a standalone library
  • Parrot's the first test of a standalone system

Nicholas:

  • nice that it doesn't count against TPF's slot list

Jesse:

  • and it's nice visibility for Parrot from another group

Jerry:

  • I finally have six weeks of no plans to travel
  • should be able to devote more time to Parrot and Rakudo
  • looking forward to that

Larry:

  • getting some hacking in on my two pet bugaboos, the longest token matcher and match object generator
  • I refactored the matcher
  • it still uses TGE
  • instead of lumping all of the expect term possible tokens (that is, all of them) into one bucket it separates them into buckets based on their first letter
  • it's a one-level tree
  • we can build a much smaller DFA for the regexes that start with that letter
  • it caches that, of course
  • can get an instant reject if the next token can't possibly start with that letter
  • also flattened out all of the rules such that the list of tokens is easy to read
  • if the first probe with the DFA engine fails, I can take that small set of tokens that start with the same letter, run all of those rules, and sort from longest to shortest
  • preserves the token matching order without building huge DFA structures
  • as a backoff strategy, that will scale pretty well
  • refactored the parameter passing on the matcher side (STD 5)
  • instead of passing an initial array of random things, I have parameters
  • constructs match objects more correctly
  • in the sense that it gets all the information it's supposed to have
  • also has some attachments where it shouldn't have
  • I'm cleaning that up
  • that should scale pretty well

Jerry:

  • is there a drop in memory usage?

Larry:

  • I haven't measured
  • I'm sure that not feeding 800 regexes to TRE at once will make it allocate 17 megabytes on the stack
  • it might still be allocating too much for some of the larger things
  • I'm still aiming for correct, as opposed to fast
  • just trying to bear fast in mind
  • the longest token matcher now returns a linked list of states
  • not a string
  • should be a lot faster; easier to cache
  • functionally it's the same as before
  • one of those things you don't even have to measure to know it'll be faster
  • trying to avoid the bugaboo of premature optimization by doing what I know will be efficient to begin with
  • all the while trying to make the thing work
  • it has a good chance of being pretty speedy
  • my talk in Tokyo will be about all of the places where the current grammar allows extensibility
  • it'd be nice to be able to demonstrate some of that

Allison:

  • getting work done again
  • launched the Strings PDD
  • list of tasks for concurrency that I'm breaking down into smaller pieces
  • may post what I have now, and leave other people to break them down

Patrick:

  • are they parallelizable? :)

Allison:

  • many of them are
  • there are some bigger things, like switching the exception system over to the event handler
  • otherwise, just life stuff

Patrick:

  • had paying work come up this past week, so not a lot of actual coding
  • need to type the milestones document
  • it's all in my head
  • managed to remove a lot of unused code thanks to chromatic's post about possible optimizations
  • mostly just cleanup
  • but helped me figure out things which will feed into my redesign of PGE for longest token matching
  • should be able to return to direct Rakduo hacking later this week

Will:

  • various Parrot cleanups
  • TPF quarterly grant proposals are due at the end of the month
  • haven't seen anything come in yet

Allison:

  • they're queued in an RT queue
  • I don't know if grant members have access to that queue

Will:

  • we do
  • please, get your proposal in now, sooner than later
  • that goes for you on the call as well as people reading the minutes

c:

  • mostly spent the past week optimizing Parrot and Rakudo
  • looks like it's the building speed is twice as fast as when I started
  • runtime is faster too, but the optimization is compilation time
  • found some infelicities that need more design thought
  • but I'm happy to put these improvements in now and take them out later when the design improves around them
  • hope to start adding new features again soon

Patrick:

  • most of the test execution time is in compilation
  • how useful would it be to compile Rakudo to standalone PIR?

c:

  • I'd find it useful
  • but I'd find about ten things useful with all I work on
  • so not a blocker at the moment

Jesse:

  • how far will that get you toward native executables?

Patrick:

  • the existing trick for building perl6 would work
  • but it's not the same

c:

  • if it takes an hour or two, it would help me with debugging and profiling
  • if it takes more time, it's not that important

Patrick:

  • we have to figure out runtime deployment issues for the Perl 6 runtime library

Will:

  • we could add the requirement to run from languages/perl6/ right now

c:

  • that's fine by me for now

Patrick:

  • that's an afternoon job, not too bad
  • what do we need to do to get the Perl 6 and Parrot pages up to date?

Will:

  • I'll work on that

Nicholas:

  • why is C99 useful to Parrot and the compiler tools?

c:

  • front-end parsing for C header files to build NCI declarations automatically
  • the backend is pretty easy, that's thunk generation
  • the front-end keeps people from having to write boilerplate code by hand
  • generate the front-end once, where you have the headers, and then you can run the generated code anywhere even if you don't have the headers

Jesse:

  • how does that compare to Python's ctypes?

c:

  • as I understand it, they have the nice backend stuff
  • not so sure about the front-end
  • my P5NCI is nicer, if incomplete
  • just haven't had time to work on it...

Jesse:

  • if you put in for a TPF grant, that would be very useful

c:

  • get me a clone first, and you have a deal

Jerry:

  • Allison, we talked about implementing return
  • that requires tying in exceptions to the concurrency scheduler?

Allison:

  • yes
  • just not implemented yet
  • when we did exceptions, we didn't have concurrency
  • so it's on the top of my list to tie them together

Will:

  • Tcl's already using exceptions to handle return, break, and continue

Allison:

  • right now, you can't have an exception handler which is a full subroutine

Patrick:

  • I'm not sure we need one for that feature
  • every subroutine block decorated as such in PAST puts an exception handler in the block
  • if any nested block throws a return type exception, it grabs the arguments, does what it has to, and then does a Parrot return

Allison:

  • if that's what you need, go ahead and do it
  • I thought there are some features you didn't have yet

Patrick:

  • I thought there might be some opcodes I needed, like handled
  • but we can do something now
  • might not be completely optimal
  • but it's just packaging things up now
  • I have something I think will work
  • it's not trivial, but I'm 80% confident
  • just a matter of sitting down and doing it

Allison:

  • the concurrency stuff will be there before the next release
  • might not want to roll it in before the release
  • but it'll be there soon

Patrick:

  • I want to get return in for the April 15 milestone we're behind on

Jerry:

  • have you put in tickets for the breakdown of specific tasks?

Allison:

  • I've never done tickets for that
  • just sent mail to the list of the tasks
  • handed them out to people as they volunteered

c:

  • can you put them on a wiki page?
  • some of the other committers wanted that

Allison:

  • I can do that
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