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Sat, 02 Jul 2011

How fast is Rakudo's "nom" branch?


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Nearly one year ago, the Rakudo Perl 6 developers proudly released the first Rakudo Star, a distribution aimed at showing the world what Perl 6 can look like, and in turn get feedback from more early adaptors.

And feedback we got. While the overall response was very positive, people had one main concern: it was too slow. That didn't come as a surprise, considering that we had focused on features first. Now it was time to change that, and work on massive performance improvements.

That is easier said than done. One of the reasons is that Rakudo is tightly coupled to the parrot virtual machine, but there is a lot of mismatch between the two. For example parrot provides multi dispatch built-in, but not quite with the semantics that Perl 6 needs. Same for parameter binding, objects and a number of other areas.

In the following year, parrot got a new, faster garbage collector, and Jonathan Worthington came up with a cache for type checks at routine call time.

This sped up this simple mandelbrot fractal generator at size 201x201 from 18 minutes to 16 minutes 14 seconds. Actually the speedup was better than that, but we paid a performance penalty for new features, bug fixes and parrot performance regressions.

But it was clear that more substantial improvements where needed. One of the most promising candidates for speedups is a complete redesign of the object model, resulting in the "nom" (new object model) branch of Rakudo. Additionally to providing much more well suited OO primitives than parrot can offer right now, it also allows to share more information between compile time and run time, making a lot of optimizations possible.

Yesterday I sped up some operations on Complex numbers, and implemented a built-in that was missing to run the mandelbrot script. And today I timed it: 3 Minutes. From originally 18 Minutes.

Now that's a speedup by more than a factor of 5. I'm not sure if it will extend to other operators, but it sure is encouraging.

And that's without the optimizations that will now be possible, for example inlining operators. So after a literally slow start, Rakudo Perl 6 has a bright and fast future ahead. And it's already here, just not evenly distributed.

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