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Comment by WildUtah | Hacker News Reader

It's fairly easy to get C performance (and even beat it in concurrent code) for the same amount of effort on the JVM.

Ha.

That's what we were promised back in the mid-1990s. It's no more true today than it was then. Well written Java will always be about 2-4x slower than similar C code.

JVM applications have many compensating advantages, including the aforementioned ease of exploiting concurrency. That doesn't erase the reality of single thread performance where Java has never, in twenty years of strong expert effort, caught up.

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Agreed, in that the performance benefits you can get out of a higher level language will often depend on the stuff where the limits of human cognition is the performance boundary. As computing gets faster in general, the practical considerations should shift more towards the performance you can get out of an entire system than unit-for-unit performance. On that level, human comprehension often seems to be what needs to be accounted for.

I think of it as problem akin to how you can make traffic run better in an entire city rather than optimising the performance of an engine in a single car. It doesn't invalidate making more performant engines, but it's a different level of consideration.

When saying, "JVM is as performant as C", it's easy to run the numbers and see whether it's true or not, objectively. The caveat that GP throws in is, for the same amount of effort. Then you need to specify which human and under what circumstances, and the entire thing gets hairier.

As computing gets faster in general, the practical considerations should shift more towards the performance you can get out of an entire system than unit-for-unit performance.

Those days are over, unfortunately. Computing stopped getting faster in general around 2010. And that also changes the calculus around single thread performance. You can no longer count on hardware eventually to solve performance problems.

And this is why parallel/concurrent computing/applications are necessary to ease speedups. And that's what the new languages promise to let you get right. For the same effort.

Which is precisely why it matters that I can write functionally pure code that is trivial to parallelize. At $FORMER_WORK, I even wrote (the same!) code as reasonably idiomatic-looking Clojure (essentially, reducer fns) that transparently runs locally single-threadedly, multi-threadedly, and on Hadoop.

That C program might be fast, but it's not a great tool for processing petabytes of data on a stampeding herd of angry elephants. So, I think performance arguments need a little nuance about what you're doing.

(My experiments include soft real time with deadline scheduling. Clojure's fine.)

I can't remember the source, but I remember reading about a case where someone replaced a large hadoop cluster with one node running highly tuned C. Distributed computing comes with a lot of overhead and you might be surprised at just how much you can get out of a highly tuned C application.

> Well written Java will always be about 2-4x slower than similar C code.

Nope. A large, concurrent app is likely to be faster in Java given similar effort (of course, given enough effort -- which may be double -- C will eventually surpass that, sometimes even significantly, depending on usage). Currently the main bottleneck, which makes the above statement very dependent on application type, is lack of value types, and that's being addressed. In small sequential apps, there will be a significant advantage to C, which diminishes with the size of the app. The reason is that as the app grows, it gets harder to write manual optimizations while keeping the code modular and maintainable, while HotSpot can do all sorts of optimizations even with nice abstractions.

See my comment here: https://news.ycombinator.com/item?id=13349838

I "kinda" agree with you. Java has the right stability and speed trade offs and can be wicked fast. It beats the crap out of most garbage collected languages save maybe .net and the CLR.

For real applications I agree with you that c is the way to go. Java with c and off heap memory gets you a pretty long way.

It depends on the application domain and the developer skills.

In many domains it doesn't matter you can do it in 10ms in C and I do it in 1s in Java, if the customer is willing to wait 5s.

Also I see all the time badly written Java code. For example copying an array via for loop, instead of System.arrayCopy.

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