github.com/moarvm/moarvm | IRC logs at colabti.org/irclogger/irclogger_logs/moarvm
Set by AlexDaniel on 12 June 2018.
nine moon-child: those errors are hard and a single core dump most likely won't be enough. Can you post code somewhere that reproduces this issue (even if only sometimes)? 05:48
moon-child nine: github.com/moon-chilled/SEProxy/bl...seproxy.p6 06:23
it's quite innocuous (though not very well written)
another thing: I was using mvm from a few months ago; just updated it. Might that be the issue? 06:24
another thing: I'm on freebsd
nine Yes, a newer MoarVM may already have a fix (as well as new bugs...) 09:10
nwc10 good *, #moarvm 09:11
nine good weekend! 09:40
timotimo good *9 09:53
MasterDuke rainy weekend here 10:09
nwc10 currently sunny, but wind threatened 10:10
dogbert17 m: say "Hi #moarvm" 14:03
camelia Hi #moarvm
dogbert17 does anyone know if the following debugserver function is in fact used? github.com/MoarVM/MoarVM/blob/mast...ver.c#L146 14:04
timotimo ^^ 14:05
my reason for asking is that it seems as if the last parameter, i.e. 'MVMuint32 *file_idx' has not been properly initialized 14:08
see github.com/MoarVM/MoarVM/blob/mast...rage.c#L61 and line 22 in the same file 14:09
MasterDuke how could i end up in this branch (assuming the `|| 1` wasn't in the if)? i.e., how can i call `%` with two bigints that have smallint values? 14:24
dogbert17 MasterDuke: what branch? 14:39
MasterDuke oh, ha. github.com/MoarVM/MoarVM/blob/mast...#L543-L545 14:40
dogbert17 I'm note sure I understand. Do you want to use the else branch if the two operands are small? 14:47
MasterDuke yeah. it's currently disabled by the `1 ||` because the standard c `%` operator doesn't work for us, but i want to try and create a working smallint version 14:48
but i can't seem to get to the function at all without having actually big bigints 14:49
dogbert17 is it the size of a number which makes a bigint big? 14:54
dogbert17 hello brrt 14:58
brrt hi dogbert17
dogbert17 MasterDuke: does commit 8e9761efb3e give any clues? 15:04
brrt: are local variable, which are not explicitly initializes, undefined in c? 15:06
*variables 15:07
nine yes
dogbert17 nine: any comment wrt to the stuff I wrote here an hour ago, have I misunderstood what's going on?
brrt dogbert17: yes, undefined 15:15
in practice, without optimization, garbage values;
under influence of optimization pretty unpredictable
I think some compilers default to setting to zero 15:16
but don't rely on it
dogbert17 brrt and nine: thank you 15:17
MasterDuke: seems as if MVM_bigint_mod is bypassed if the numbers are small 15:31
MasterDuke yeah
but is that always going to be the case? if it's guaranteed never to happen, we can simplify. if it's just some combination of optimizations, codegen, etc that means we haven't been able to trigger it in practice, it has to stay 15:35
i tried stuff like `my Int $a = 2**66 + 5; my Int $b = 2**67 + 3; say ($a - 2**66) % ($b - 2**67)`, but no dice 15:37
i can if i call nqp::mod_I directly, but why isn't it being codegenned? 15:38
moritz sounds like to be able to know for certain you don't need the bigint variant, you must know the value of the operands. If you know that at compile time, you can just constant-fold it away 15:44
MasterDuke github.com/rakudo/rakudo/blob/mast...#L375-L392 15:51
dogbert17 mod_i vs mod_I 15:52
MasterDuke that can probably be simplified if i get a working small bigint version. might be faster then without all the extra hll code 15:53
brrt mind that mod_i is not a very fast opcode because the underlying idiv is a slow, slow, slow operation 15:56
(presumably because of this, everybody optimizes it away; presumably because of that, intel/amd get away with not optimizing)
bbiab 15:57
brrt \o 18:20
nwc10 o/
brrt One of the things that stuck to me when I read the long javascript article that MasterDuke shared some time ago... 19:19
Their interpreter is written in assembly (with macros, and 'machine independent', so far as possible)
luajit has the same thing
and ... truth be told it's really a good idea 19:20
timotimo have you had any look at jitter? ageinghacker.net/git/cgit.cgi/jitter 22:24
it looked like it has a few cool tricks up its sleeve
there was a presentation about it, i saw it on video, but i'm not sure where i found the link 22:30
ageinghacker.net/talks/jitter-slide...-08-25.pdf or perhaps i have really only seen the slides?
andhallucinated the video 22:31
moon-child timotimo: I've heard of it. I hear it's not actually that fast, though. And (iirc) it wouldn't let you do type specialization or anything like that 22:32
timotimo oh,hm 22:33
we get a lot of our speed even if jit fails from type specialization
the developer of gnu poke uses jitter, maybe that'sa good place to ask,if not where-ever jitterusershang out 22:35
MasterDuke yep. github.com/rakudo/rakudo/blob/mast...#L375-L392 is now just `nqp::if(b, nqp::mod_I(nqp::decont(a),nqp::decont(b),Int),Failure.new(X::Numeric::DivideByZero.new(:using<%>, :numerator(a))))` and `my $a; for ^1_000_000 { $a = $_ % ($_ + 2) }; say now - INIT now; say $a` goes from 0.16s to 0.088s. passes a spectest 23:12
timotimo oh my 23:16
that is from switching libtommath for gmp?
hum.does $_ % ($_ + 2) alwaysresult in $_? maybenot for negatives 23:17
oh, or is thatfrom putting a "no big integer needed" path in there by having it inside the implementation of mod_I? 23:18
could you look at numbers above 2 ** 32?
because those would be handle-able by mod_i,but will have a realbigint formod_I

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