Re:Why Python Is Slow: Looking Under the Hood
by jerf on Tuesday November 18, 2014 @06:17PM
(#8627048)
"Javascript, however, is not really slow anymore."
What's easy to lose track of under the steady stream of headlines about this microbenchmark going 5x faster and that microbenchmark going 10x faster and this one microbenchmark being "faster than C" is that Javascript is still a fairly slow language, though. Flick that to compare Javascript vs. C: http://benchmarksgame.alioth.debian.org/u64/benchmark.php?te...
It has come a long way. It is, of course, still usable for many things. But it is still an interpreted language, and my guess is that we've basically plateaued on performance for Javascript, and it's important to remember that it isn't as "fast as C" in any useful sense of the term. And for that matter, to get even that performance out of JS seems to require you to write a very specialized subset of JS that will tickle the optimizers correctly. In practice I suspect you will get even worse deltas over C, which, for all of its many failure modes, does make it often easier to do the fast thing than the slow thing, usually regardless of the correctness of either of them.
(That's why we have asm.js, after all. You can't have both of "Javascript is as fast as C" and "asm.js is several times faster than Javascript", because the composition of both statements is absurd.)
What's easy to lose track of under the steady stream of headlines about this microbenchmark going 5x faster and that microbenchmark going 10x faster and this one microbenchmark being "faster than C" is that Javascript is still a fairly slow language, though. Flick that to compare Javascript vs. C: http://benchmarksgame.alioth.debian.org/u64/benchmark.php?te...
It has come a long way. It is, of course, still usable for many things. But it is still an interpreted language, and my guess is that we've basically plateaued on performance for Javascript, and it's important to remember that it isn't as "fast as C" in any useful sense of the term. And for that matter, to get even that performance out of JS seems to require you to write a very specialized subset of JS that will tickle the optimizers correctly. In practice I suspect you will get even worse deltas over C, which, for all of its many failure modes, does make it often easier to do the fast thing than the slow thing, usually regardless of the correctness of either of them.
(That's why we have asm.js, after all. You can't have both of "Javascript is as fast as C" and "asm.js is several times faster than Javascript", because the composition of both statements is absurd.)