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Welcome to the main channel on the development of MoarVM, a virtual machine for NQP and Rakudo (moarvm.org). This channel is being logged for historical purposes. Set by lizmat on 24 May 2021. |
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| Nicholas | good *, #moarvm | 06:33 | |
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| lizmat | good after* ! | 10:26 | |
| jnthnwrthngtn might find this PR interesting: github.com/rakudo/rakudo/pull/4918 | |||
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| vrurg | Anybody to advise on serialization? | 19:45 | |
| Nicholas | I don't know what the question is yet, so I don't know if I can actually answer usefully | 19:46 | |
| "use Sereal rather than Storable" - oh, very wrong channel | 19:47 | ||
| vrurg | ;) | ||
| I just wonder if it is possible to detach an object from serialization context. | 19:48 | ||
| Nicholas | I have no idea about that | ||
| (Sorry) | |||
| vrurg | nine: ping? | 19:49 | |
| Too late, perhaps. | |||
| Nicholas | I sort of assumed the same - he's not normally around at this time of the morning | 19:50 | |
| vrurg | C'mon, it's just 11 in Germany! Even me is woken up at this time! | 19:51 | |
| Normally... | |||
| MasterDuke | Nicholas: do you know anything about MVM_string_compute_hash_code and whether there are any easy optimization possibilities? | 19:52 | |
| hm, it doesn't have a whole lot of code in it... | 19:53 | ||
| Nicholas | I don't know anything about that code (as in, I've read it breifly previously, but never needed to touch it) | 19:56 | |
| nine | pong | 19:57 | |
| vrurg | nine: if I do `nqp::setobjsc($obj, nqp::null())` – would it throw, or exclude the object from serialization? | 19:58 | |
| nine | I don't think it's possible to detach an object once it's in a serialization context. It is possible to prevent it from getting attached. There's also nqp::neverrepossess | 19:59 | |
| Maybe take a step back and describe your problem? | |||
| vrurg | I'm trying to make symbol merging on Stash more thread-safe by clone - replace $!storage. But when it happens compile time the clone gets lost. If I add it to serialization – the original would still pollute the bytecode. | 20:00 | |
| nine | What do you mean by "pollute the bytecode"? | ||
| vrurg | Both hashes: the original $!storage and its modified clone would be serialized. | 20:01 | |
| nine | Why would the clone get lost if it's referenced from the Stash object? | 20:02 | |
| MasterDuke | just throwing out random words here, but are nqp::scwbdisable and nqp::scwbenable relevant? | ||
| vrurg | It does. Until I added $*W.add_object_if_no_sc($storage) I was experiencing lost symbol tables for `use NativeCall::Compiler::GNU` and alike. | 20:04 | |
| nine | But why? | ||
| vrurg | MasterDuke: no because there is a need to replace an already serialized object. | ||
| nine: No idea. Let me create a gist with the method code. | |||
| gist.github.com/vrurg/b7dcda63d288...9c4151d6a7 | 20:06 | ||
| It is experimental. The idea for now is ModuleLoader.merge_globals calls this method on Stash'es to let them wrap merging into a lock. | 20:07 | ||
| MasterDuke | Nicholas: btw, what does Perl use? | ||
| Nicholas | what what does Perl use? hashing algorithm? | ||
| vrurg | nine: oops, just've noticed that I forgot to uncomment cloning. Perhaps I'm wrong. | 20:08 | |
| MasterDuke | yeah | 20:09 | |
| vrurg is recompiling... | |||
| MasterDuke | particularly for strings, if those are done differently | ||
| a perf report of `say "big2.txt".IO.slurp.lc.words.Bag.elems` has MVM_string_compute_hash_code as the second most expensive function | 20:10 | ||
| and MVM_string_compute_hash_code kind of has just two parts to it, the string iteration and the hashing. i can't easily do anything about the string iteration, but maybe there's something better than siphash | 20:12 | ||
| vrurg | nine: sorry, false alarm. It's not about serialization, after all. | ||
| Nicholas | all things in Perl are hashed as strings. And I've lost track of what is now used. Yves did a lot of work to make it flexible (at C copile time) | ||
| but the choices weren't just Siphash. (And IIRC "Siphash" defaults to something like Siphash 2-4, where the "2" and "4" refer to rounds for each loop iteration, and rounds during finalisation.) | 20:13 | ||
| MasterDuke | perldoc.perl.org/perlsec#Algorithm...ty-Attacks says siphash is the fallback, but the default is much faster (though it doesn't say what that is...) | 20:15 | |
| ah, for my machine at least (using the system perl), `PERL_HASH_SEED_DEBUG=1 perl -e ''` gives `HASH_FUNCTION = SBOX32_WITH_SIPHASH_1_3` | 20:17 | ||
| Nicholas | I should go to bed (evil alarm clock goes off too soon) but I *thought* the default was 1-3, not 2-4 | 20:18 | |
| the Perl 5 default, that is. | |||
| japhb remembers back when it was "multiply by 33, add, shift" | |||
| Nicholas | :-) | 20:19 | |
| Nicholas remembers when it was Kindergarten, and it didn't totally matter when you arrivedd, but "before 9" was generally good. | |||
| I don't appreciate the "good morning" from the alarm clock | |||
| japhb | My biggest problem with alarm clocks is training myself to hit snooze when I'm mostly asleep rather than turning it off completely. | 20:21 | |
| vrurg | Respect to iphone, where 'stop' is a little gray button, hard to click accidentally. Though, I have this achievement unlocked for several times... | 20:23 | |
| MasterDuke | hm, github.com/google/highwayhash looks interesting | ||
| japhb | vrurg: On Pixel, it's swipe center-to-left or swipe center-to-right. Which is especially annoying when the alarm is going off and you're too tired to get your finger to sufficiently match "center" at the start | 20:24 | |
| (Meanwhile your panicing mind is reminding you that your partner is *also* having to hear the alarm that won't stop.) | 20:25 | ||
| MasterDuke | sadly, i sort of look back fondly on when i used to set an alarm clock. i now only set one a couple times a year, kids get us up early enough (for pretty much anything scheduled during the day) otherwise | 20:27 | |
| nine | We now make it through stage parse of Test.pm6 on RakuAST (including BEGIN time effects like traits and proto auto-generation). | 20:45 | |
| MasterDuke | cool beans | 20:46 | |
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| jnthnwrthngtn | nine: Wow, that's some progress :) | 21:20 | |
| MasterDuke | Nicholas: does Perl ever not compute the hash code if the string is too large? | 22:01 | |
| jnthnwrthngtn: you might have some intuition here. for this example `say "big2.txt".IO.slurp.lc.words.Bag.elems` (where big2.txt is a collection of random stuff, e.g., project gutenberg text, wikipedia text), a lot of time is spent in MVM_string_compute_hash_code | 22:03 | ||
| in 1095695 of the cases that MVM_string_compute_hash_code is called, the storage type is MVM_STRING_STRAND, two strands, with 4 graphs in the first strand and 6488666 graphs in the second | 22:05 | ||
| the next most common case for two strands with 21 occurrences is 7 graphs in the first and 15 graphs in the second | 22:06 | ||
| any idea why the case with 6488666 graphs in the second strand would be happening so frequently? | 22:08 | ||
| jnthnwrthngtn | MasterDuke: First guess: Bag uses an object Hash, and thus .WHERE/ObjAt. The WHERE value is formed of "Str|the value", the "Str|" is the first entry in the strand. Look carefully at the second strand, I bet it's got offsets, since substr is generally non-copying rather rather produces a strand. | 22:09 | |
| s:1st/rather/and | |||
| sourceable6 | jnthnwrthngtn, No idea, boss. Can you give me a Code object? Output: 4===SORRY!4=== Error while compiling /tmp/YzdXnm6TNmConfusedat /tmp/YzdXnm6TNm:1------> 318⏏4st/rather/and expecting any of: whitespace | ||
| jnthnwrthngtn | These indices are what I refer to: github.com/MoarVM/MoarVM/blob/d11b...ring.h#L58 | 22:10 | |
| MasterDuke | hm, let's see what those values are... | 22:11 | |
| ah yes. now i see that all the calls have different start and ends | 22:14 | ||
| jnthnwrthngtn | lizmat: Missed this before, but: "what makes the NEXT phaser different from e.g. LAST" - it's that in NEXT we can be 100% sure that we ran the outer block (because if there's a next value, there was a loop iteration), but `LAST` need to run even if we didn't have any values, so we need some kind of hack to cope with it | 22:16 | |
| lizmat | ah, ok | ||
| well, I figured it out in github.com/rakudo/rakudo/pull/4918 | 22:17 | ||
| which in turn lead me to github.com/rakudo/rakudo/pull/4919 | 22:18 | ||
| meanwhile, /me is going to get some shuteye & | 22:19 | ||
| MasterDuke | hm, so i guess the time spent in MVM_string_compute_hash_code is because of the number of calls and their total cost, not because it's being called (multiple times) on a large string | 22:20 | |
| yeah, vast majority of the number of graphs actually being checked are <20 | 22:22 | ||
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