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Re^10: Modernizing the Postmodern Language?

by b2gills (Novice)
on Jul 06, 2020 at 22:50 UTC ( #11118985=note: print w/replies, xml ) Need Help??


in reply to Re^9: Modernizing the Postmodern Language?
in thread Modernizing the Postmodern Language?

Can you explain why Perl is sometimes slower than Raku then?
$ time perl -e 'for (1..1_000_000_000) {}' real 0m30.291s user 0m30.256s sys 0m0.020s $ time raku -e 'for (1..1_000_000_000) {}' real 0m12.407s user 0m12.436s sys 0m0.040s

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Re^11: Modernizing the Postmodern Language?
by chromatic (Archbishop) on Jul 06, 2020 at 23:24 UTC

    Because Raku has a better internal representation for integers than Perl's SvIV and can manage ranges lazily without reifying a large data structure. (I can't remember right now if Perl optimizes this in recent releases.)

    I don't know what doing nothing a billion times in 12 or seconds has to do with my point that the semantic mismatch between a language and a target platform is difficult to manage, however.

    You can port Raku to LLVM or Node or Inferno or whatever platform you want, but unless that platform can optimize grammars that require dynamic dispatch for every individual lexeme, you're going to end up with a slow Raku.

      I can't remember right now if Perl optimizes this in recent releases.

      I don't think so - and same goes for raku, apparently.
      On Ubuntu-20.04 (perl-5.32.0):
      $ perl -le '$x = time;for (1..1000000000) {}; print time - $x;' 51
      On Windows7 (perl-5.32.0):
      C:\>perl -le "$x = time;for (1..1000000000) {}; print time - $x;" 13
      The Windows box is about twice as fast as the Ubuntu box, so I'm not sure why the difference in this case is a factor of 4.

      Anyway, thankfully perl has XS/Inline::C at hand to enable sane and efficient handling for cases such as these.

      Cheers,
      Rob

      A question in my mind is: can Perl's internals be re-written for more efficiency, given all this experience gained over the years in these parallel attempts? Equally important: an API to access the internals a la XS. Obviously easier, user-friendly, perhaps "isolating" the core better?

      One point of view is by salva here Re^4: Modernizing the Postmodern Language?. Is yours different? Is there hope?

        Can they be rewritten? Yes. It's just code.

        Replacing XS is a big deal though. That's a bigger break than syntax, because 30% of the CPAN won't work with new releases.

        Nicholas Clark's Ponie work shows one way where it's difficult. Artur Bergman ran an experiment around the same time to migrate SVs to something more like Parrot's PMCs, where every data type had virtual methods in well-defined slots instead of accessor macros. That didn't go very far either. These are fundamental assumptions of perl's implementation without any encapsulation beyond C macros.

        It'll be a lot of work.

        The best way I've ever figured out to do this is to introduce an abstraction layer for XS that's not XS and that lets the core gradually migrate away from the XS-ish implementation, but even that's a decades-long project I fear.

      So in other words, Raku is a better designed language.

      Actually no. That is not the correct view.

      Raku is actually a designed language. Perl is an accumulation of parts that mostly work together.

      The main reason grammars are slow is because basically no one has touched the slow parts of it for the better part of a decade. We have some knowledge about how to speed it up because earlier prototypes had those optimizations.

      The thing is, that it isn't that slow. Or rather it isn't that slow considering that you get an actual parse tree.

      If you must know, the main reason it is slow is probably because it sometimes looks at particular tokens perhaps a half-dozen times instead of once. (This is the known optimization that was in one of the prototypes that I talked about.)

      It has absolutely nothing to do with being able to replace what whitespace matches. That is already fairly optimized because it is a method call, and we have optimizations which can eliminate method call overhead. Since regexes are treated as code, all of the code optimizations can apply to them as well. Including the JIT.


      Really if Perl doesn't do something drastic, in five to ten years I would suspect that Raku would just plain be faster in every aspect. (If not sooner.) The Raku object system already is faster for example. (And that is even with MoarVM having to be taught how Raku objects work every time it is started.)

      Something like splitting up the abstract syntax tree from the opcode list. That way it can get the same sort of optimizations that Raku has that makes it faster than Perl in the places where it is faster.

      Imagine if the code I posted would turn into something more like this:

      loop ( my int64 $i = 1; $i <= 1_000_000_000; ++$i ) {}
      Or rather transform that into assembly language. Which is basically what happens for Raku. (Writing that directly only reduces the runtime by a little bit more than a second.)

      It seems like every year or two we get a new feature or a redesign on a deep feature that speeds some things up by a factor of two or greater. Since Perl is more stratified than designed, it is difficult to do anything of the sort for it.


      Also I don't know why we would want to downgrade to LLVM. (Perhaps it can be made to only be a side-grade.)

      As far as I know LLVM only does compile-time optimizations. The thing is that runtime optimizations can be much much better, because they have actual example data to examine.


      Perl is an awesome language.
      Raku is an awesome language in the exact same ways, but also in a lot more ways as well.
      Many of those ways make it easier to produce faster code.

        Also I don't know why we would want to downgrade to LLVM.

        That wasn't the point of my post, but it was also exactly the point of my post, so I'm not sure why we're having a discussion on how Raku will someday eventually be faster than Perl, because that's irrelevant to my point that the semantic mismatch between a language and its implementation is really, really important to performance.

        The main reason grammars are slow is because basically no one has touched the slow parts of it for the better part of a decade.

        I remember profiling and optimizing grammars in an earlier version a little over a decade ago, so.

        It has absolutely nothing to do with being able to replace what whitespace matches.

        I don't believe this, because:

        • Like I said, I spent a lot of time looking at this.
        • Doing nothing is faster than doing something. A JIT is not magic fairy dust that makes everything faster. Even if you can get this codepath down to where you can JIT across a monomorphic call site, the resulting code is still not faster than a single inlined lexeme, especially if you account for the time and memory overhead of JITting at all. The semantic mismatch between a language and its implementation is really really important to performance.
        Really if Perl doesn't do something drastic, in five to ten years I would suspect that Raku would just plain be faster in every aspect.

        I've heard this every year for the past 10 years, but I respect that you're not promising it in the next year, like Raiph always used to. I'll believe it when I see it.

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