Perl 6 - the future is here, just unevenly distributed

IRC log for #moarvm, 2016-06-30

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Time Nick Message
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03:17 travis-ci MoarVM build errored. Jonathan Worthington 'Merge branch 'new-multi-cache''
03:17 travis-ci https://travis-ci.org/MoarVM/MoarVM/builds/141061323 https://github.com/MoarVM/MoarVM/compare/419c4a5ed6e9...8fc21d50aa4f
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03:56 geekosaur ... wat
06:51 nine Build failures seem to be a failed download of perl 5.14 on a worker
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11:31 brrt hmm, C optimizers aren't all they're cracked up to be
11:32 brrt case in point, i kind of know the ideal assembly code for a routine i'm writing, and neither clang nor gcc will make it
11:32 jnthn Optimizers are often fairly cracked up :P
11:32 brrt indeed
11:33 brrt yesterday i overhead a normal person saying 'optimization' in a context that almost made sense
11:33 brrt what have we done to the world
11:34 jnthn ;)
11:35 brrt i have the sequence: return a->foo == b->foo ? a->bar - b->bar : a->foo - b->foo; the point is to sort by field foo then bar
11:35 brrt i can implement this as mov, sub, jne, mov, sub, ret
11:35 brrt because the sub sets the flags for the jump to use
11:36 brrt what they will make is close, but not the same
11:36 jnthn I suspect this is part of my luajit writes its interpreter in assembly :)
11:36 jnthn *why
11:37 brrt right :-)
11:37 brrt well, i know of another reason
11:37 jnthn Also, how confident are you that what you've got will perform better than what the C compiler produces?
11:37 jnthn (Noting that, sure it's less instructions, but after ILP and stalls have effect?)
11:38 brrt if your interpreter is written in assembly, then your JIT and interpreter can be made to agree where 'special' variables are stored and what your stack layout looks like
11:38 brrt fair point
11:38 brrt it probably makes very little difference
11:39 jnthn Yeah, that's also true.
11:39 jnthn Though it's also the kind of coupling that tends to concern me :)
11:39 brrt that... well... i...
11:39 brrt it's complicated
11:40 brrt that kind of coupling, not just in CS but accross technical projects, is where you can get *huge* performance gains
11:40 brrt the most basic version of that is a train vs automobile
11:40 brrt sure the train is heavier, but it has much less specific resistance, hence it is more efficient
11:41 brrt the same principle also works within computer programs
11:43 brrt if you can edit your database rows in place, then you are going to be /much/ more efficient than if you have to load them, marshall and unmarshall them over a socket, submit commands, parse commands, etc.
11:43 brrt but yes, that does give you much more coupling, and a design that is much more difficult to change
11:47 brrt fwiw, i don't think it is worth rewriting moarvm in assembly
11:47 brrt i might be interested in doing a toy project like that, but just as a toy
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12:32 nwc10 So, what should I used to make slides? http://act.yapc.eu/ye2016/talk/6754
12:34 lizmat nwc10: I don't care, I wanna see this in whatever form you put it in!
12:34 lizmat ++nwc10
12:44 nwc10 the slides need to *work*, because there's enough to say that the slides mustn't get in the way
12:49 nwc10 also, pre-apology - my alternative history runs out of steam in about 2012. There weren't any more good jokes or observations to make.
12:49 lizmat yeah, I seem to have that effect on people  :-)
12:54 nine nwc10: typo "In this tall we'll learn"
12:54 nwc10 ooops.
12:54 nwc10 nine++
12:55 nwc10 oooh, bait and switch
12:55 nwc10 I can still edit it :-)
12:55 nwc10 "this space for rent"
13:03 jnthn ;-)
13:13 nwc10 lizmat: "vote for me!"
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19:25 brrt nwc10++ very cool, very sorry i'm going to miss that
19:25 brrt last time i made slides with beamer and was happy enough about it
19:25 brrt but then i didn't use much images
21:23 timotimo the compressed archive of minimized crash cases for moarvm found by afl has surpassed 1 megabyte now
21:23 timotimo about a thousand files
21:33 jdv79 moarvm crashes that much huh?
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21:42 timotimo hah
21:42 timotimo well, there's one particular thing that it finds over and over again
21:42 timotimo which is that you can give arg_* any index you want, even if it's far outside the valid range
21:42 timotimo we've got to hope we can easily filter those crashes out :)

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