Ideally, a good compiler that understands FP will, behind the scenes, detect when it's safe to mutate the old data rather than creating a copy. That's a big part of why Haskell manages to be neck-and-neck with C despite being functionally pure.
Where it gets tricky is in an environment like the JVM where programming in that style was not anticipated, and introducing any optimizations along these lines for the benefit of the proverbial Scala fans needs to be balanced against the obligation not to adversely impact idiomatic Java code.
That said, even without that, it's not necessarily crazy. It's just a value call: Do you believe that more functional code is easier to maintain, and perhaps value that above raw performance? I'm old enough to remember similar debates about how object-oriented C++ code should be, and to have at least encountered Usenet posts from similar debates about how structured C code should be. I don't bring this up by way of trying to weasel in some "historical inevitability" argument - these are legitimate debates, and there are still problem domains where coding guidelines may discourage, or even prohibit, certain structured programming practices. For very good reasons.
Rust gives you FP-style without loads of copies and C-like performance. Immutable data-structures aren't idiomatic, but it's ownership gives you most of the same benefits.
The nice thing about Rust is that it gives you the main benefits of FP even when you're not programming in "FP style". The Rust "sharing xor mutability" default model provides underlying semantics and ease of analysis that's quite comparable to what you get with a pure-functional language. Of course extended mutability as with Cell<>, RefCell<> etc. undermines this, but these are only used when necessary.
Would you say idiomatic Haskell is faster or slower than idiomatic use of Java and the JVM? I'm interested in actual experience and preferably benchmarks of real cases, no thought experiments please :)
(If this sounds harsh, it's not my intention. In another HN thread I had someone "explain" to me how Java and Java's OOP is "not suitable for business software development". If this seems like a bizarre statement which disregards more than a decade of business software development -- this is why I ask for actual experience and not opinions or "I think this can't be right").
Lots of people hate Java. It's unsuitable for those people.
There are certain things you might have trouble getting Java to perform, such as strict latency requirements. Another language might be more suitable for that. But that generally doesn't describe business software.
Desktop software is somewhere you probably don't want to use Java. Although if it's business desktop software, it might be a good fit since it can be cross platform (but ugly - but if it's business, it might not matter). We've built several desktop apps for warehouse computers in Java.
Getting the JVM on a machine may or may not be a hurdle. This is one of many reasons why Go is getting popular - you can just build a binary.
The positive of Java is that if you want to do something in it, someone else has probably tried. It has several large organizations backing professional quality libraries and frameworks that have had a ton of resources poured into them. It's easy to build on the shoulders of giants while relying on 3rd party libraries that don't have a bus factor of 1 - this is rare in many other languages.
If you want stability and well trodden paths, it's hard to go wrong with Java. We've had projects that continued to just work from Java 1.4 to Java 8 - a span of almost 15 years without ever having to touch the code. Java 9 was a bit of a hurdle because of project Jigsaw.
Lots of people hate Java. It's unsuitable for those people.
Understood, but I'm specifically excluding those opinions because they tell me nothing and are unrelated to suitability. Some Smalltalk folk will tell you nothing that is not Smalltalk is suitable for anything; how much would you value their opinion when determining whether a language is suitable for development?
"I hate $LANGUAGE, therefore it's unsuitable for $DOMAIN" is the lowest, less useful form of opinion. It belongs in the realm of flamewars, not of informed decisions.
Suitability to me is not related to whether I hate or like a language. I hate COBOL. I've worked with it. I'd never in a million years argue it's not suitable for banking systems, because that would run contrary to established history.
As for other applications: I agree Java is not suitable for everything. I specifically argued about business software. That said, what about Minecraft, a hugely successful desktop game? :)
Getting the JVM on a machine may or may not be a hurdle.
This was/is one of Java's mistakes. It's always been oddly hostile to JVM bundling, although some projects do so anyway (e.g. Jira). More generally, Java makes the mistake of making itself known to the user. The user is expected to install a JVM, rather than one being bundled with the application, and they're then expected to ensure it updates itself appropriately, complete with an annoying taskbar icon and always-resident auto-updater (on Windows, that is).
The user shouldn't even know the word 'Java'. Applications written in Pascal, for instance, are just applications. The user isn't made aware of the technology used.
Especially unfortunate considering that, as far as I can tell, JavaFX is really a pretty good GUI toolkit (I've only dabbled). Perhaps things will change as ahead-of-time compilation for Java becomes more mainstream.
Perhaps things will change as ahead-of-time compilation for Java becomes more mainstream
I understand JIT compilation is pretty advanced these days. Wouldn't this go against it? Or maybe the approach can be mixed, but if so, you'd still need the runtime environment ("the JVM").
A mixed approach can be done, yes. If dynamic classloading is needed, you need to bundle a JIT as well (or at least a traditional interpreter). Excelsior JET has used this hybrid approach for years. [0] I imagine it should be possible to omit the JIT if it can be determined that it's not needed.
If you ever try to write a bash script that calls a Java program in a tight loop, you'll know the limitations of a fat interpreting runtime with JIT compilation. Another relevant use case is the Stateless Lambda server-side architecture.
I believe Java (OpenJDK at least) is slow to start even if you disable the JIT and go with pure interpretation, and even if you disable runtime bytecode verification. It's just generally heavyweight and slow to get off the ground.
I imagine JIT compilation should help with this, as you suggest.
Since Java 8, there are two ways to build a binary: the javapackager tool, and the Ant JavaFX tasks (with the OpenJDK, install the openjfx package). It'll include the JRE [~50MB], and there are pros and cons with that obviously.
"One can, with sufficient effort, essentially write C code in Haskell using various unsafe primitives. We would argue that this is not true to the spirit and goals of Haskell, and we have attempted in this paper to remain within the space of reasonably idiomatic Haskell. However, we have made abundant use of strictness annotations, explicit strictness, and unboxed vectors. We have, more controversially perhaps, used unsafe array subscripting in places. Are our choices reasonable?"
“Unsuitable” doesn’t mean it can’t be done. Having written a lot of business software in Java, I actually agree it’s unsuitable. The only way I’ve been able to make it bearable is by using Lombok and pcollections.
How so? Performance? Reliability? Verbosity? Which language is suitable in your opinion?
To me this kind of opinion-based... um, opinions... fly in the face of evidence. Java has been used for more than a decade to deploy business software to great success. What more evidence does one need? It'd be like arguing "COBOL is unsuitable for banking".
In the meantime, opinions have shifted on best engineering practices, and Java has naturally run the gamut of all these opinions. And because there are tons of Java systems, there's no shortage of examples of failed/bad projects one could pick on. I wonder how many languages/platforms would have fared better...
"Unsuitable" meaning it's not a great choice. Yes, it's been done a lot (whether or not you can really say "to great success" is another matter, I think).
What I mean is that I think using Java meant the company was required to spend more resources than should have been necessary to accomplish their goal.
BTW, when I say "Java", I mean the language, not the platform. Java-the-platform is very suitable to business software. Java-the-language, less so. Java OOP brings with it a ridiculous amount of incidental complexity, boilerplate, and impedance mismatches. Of course you can make it work, I do it every day. I just think it's a poor choice. It's certainly not the worst choice, and the platform + available libraries is definitely a plus.
And as I mentioned in my original post, there are way to make it more suitable through various hacks (like Lombok) and libraries, but other languages are more suitable out of the box (including other JVM languages).
Ideally, a good compiler that understands FP will, behind the scenes, detect when it's safe to mutate the old data rather than creating a copy. That's a big part of why Haskell manages to be neck-and-neck with C despite being functionally pure.
Not talking against Haskell or FP; The disadvantage is being hard to reason about performance. Ensuring compiler will optimize something will take more cognitive load than simply writing straightforward code.
Imagine having a map() method on an array that produces another array. In a long chained pipeline of such things, compiler may be able to elide extra allocations and generate asm very near to handwritten for loops. But the abstraction breaks when the method does I/O or has side effects - you can't reorder anything in order to elide allocations. (Well this example may not make sense in Haskell because Haskell is lazily evaluated).
However there is a limit to what compiler can do, and it might manifest in edge cases like variation in order of imports. I'd rather have straightforward code than relying on compiler optimizations.
I am not arguing "against abstractions" like some Go fanboys tell you map and filter are less efficient. It is always possible to apply same map filter to iterators/lazy streams instead of arrays and get same performance in straightforward code. But that's not same as keeping in mind what heuristics compiler uses to optimize the code.
I suppose in FP/Haskell you would structure your code differently, so that it wouldn't have side effects when mapping arrays. That way you could even parallelize it trivially.
High level languages produce a lot less code than than less optimized implementations. Difficulties with reasoning about execution/performance is the penalty you potentially have to pay.
In my experience it indeed may be hard to understand performance with Haskell. That said, it comes with excellent tooling to overcome it in most of the cases.
Comments
Ideally, a good compiler that understands FP will, behind the scenes, detect when it's safe to mutate the old data rather than creating a copy. That's a big part of why Haskell manages to be neck-and-neck with C despite being functionally pure.
Where it gets tricky is in an environment like the JVM where programming in that style was not anticipated, and introducing any optimizations along these lines for the benefit of the proverbial Scala fans needs to be balanced against the obligation not to adversely impact idiomatic Java code.
That said, even without that, it's not necessarily crazy. It's just a value call: Do you believe that more functional code is easier to maintain, and perhaps value that above raw performance? I'm old enough to remember similar debates about how object-oriented C++ code should be, and to have at least encountered Usenet posts from similar debates about how structured C code should be. I don't bring this up by way of trying to weasel in some "historical inevitability" argument - these are legitimate debates, and there are still problem domains where coding guidelines may discourage, or even prohibit, certain structured programming practices. For very good reasons.
Come on... that's not what you typically get with Haskell, is it.
Rust gives you FP-style without loads of copies and C-like performance. Immutable data-structures aren't idiomatic, but it's ownership gives you most of the same benefits.
The nice thing about Rust is that it gives you the main benefits of FP even when you're not programming in "FP style". The Rust "sharing xor mutability" default model provides underlying semantics and ease of analysis that's quite comparable to what you get with a pure-functional language. Of course extended mutability as with Cell<>, RefCell<> etc. undermines this, but these are only used when necessary.
And many string types, like Haskell /s
Haskell is only close to C in extremely rare cases or when using unsafe features and the FFI.
Would you say idiomatic Haskell is faster or slower than idiomatic use of Java and the JVM? I'm interested in actual experience and preferably benchmarks of real cases, no thought experiments please :)
(If this sounds harsh, it's not my intention. In another HN thread I had someone "explain" to me how Java and Java's OOP is "not suitable for business software development". If this seems like a bizarre statement which disregards more than a decade of business software development -- this is why I ask for actual experience and not opinions or "I think this can't be right").
Lots of people hate Java. It's unsuitable for those people.
There are certain things you might have trouble getting Java to perform, such as strict latency requirements. Another language might be more suitable for that. But that generally doesn't describe business software.
Desktop software is somewhere you probably don't want to use Java. Although if it's business desktop software, it might be a good fit since it can be cross platform (but ugly - but if it's business, it might not matter). We've built several desktop apps for warehouse computers in Java.
Getting the JVM on a machine may or may not be a hurdle. This is one of many reasons why Go is getting popular - you can just build a binary.
The positive of Java is that if you want to do something in it, someone else has probably tried. It has several large organizations backing professional quality libraries and frameworks that have had a ton of resources poured into them. It's easy to build on the shoulders of giants while relying on 3rd party libraries that don't have a bus factor of 1 - this is rare in many other languages.
If you want stability and well trodden paths, it's hard to go wrong with Java. We've had projects that continued to just work from Java 1.4 to Java 8 - a span of almost 15 years without ever having to touch the code. Java 9 was a bit of a hurdle because of project Jigsaw.
Understood, but I'm specifically excluding those opinions because they tell me nothing and are unrelated to suitability. Some Smalltalk folk will tell you nothing that is not Smalltalk is suitable for anything; how much would you value their opinion when determining whether a language is suitable for development?
"I hate $LANGUAGE, therefore it's unsuitable for $DOMAIN" is the lowest, less useful form of opinion. It belongs in the realm of flamewars, not of informed decisions.
Suitability to me is not related to whether I hate or like a language. I hate COBOL. I've worked with it. I'd never in a million years argue it's not suitable for banking systems, because that would run contrary to established history.
As for other applications: I agree Java is not suitable for everything. I specifically argued about business software. That said, what about Minecraft, a hugely successful desktop game? :)
This was/is one of Java's mistakes. It's always been oddly hostile to JVM bundling, although some projects do so anyway (e.g. Jira). More generally, Java makes the mistake of making itself known to the user. The user is expected to install a JVM, rather than one being bundled with the application, and they're then expected to ensure it updates itself appropriately, complete with an annoying taskbar icon and always-resident auto-updater (on Windows, that is).
The user shouldn't even know the word 'Java'. Applications written in Pascal, for instance, are just applications. The user isn't made aware of the technology used.
Especially unfortunate considering that, as far as I can tell, JavaFX is really a pretty good GUI toolkit (I've only dabbled). Perhaps things will change as ahead-of-time compilation for Java becomes more mainstream.
They (Oracle and Java) are going the other direction on this. Jigsaw helped with JDK bundling. IntelliJ bundles its own distribution.
Excellent, I see I'm behind the times.
I understand JIT compilation is pretty advanced these days. Wouldn't this go against it? Or maybe the approach can be mixed, but if so, you'd still need the runtime environment ("the JVM").
A mixed approach can be done, yes. If dynamic classloading is needed, you need to bundle a JIT as well (or at least a traditional interpreter). Excelsior JET has used this hybrid approach for years. [0] I imagine it should be possible to omit the JIT if it can be determined that it's not needed.
[0] https://en.wikipedia.org/wiki/Excelsior_JET
If you ever try to write a bash script that calls a Java program in a tight loop, you'll know the limitations of a fat interpreting runtime with JIT compilation. Another relevant use case is the Stateless Lambda server-side architecture.
I believe Java (OpenJDK at least) is slow to start even if you disable the JIT and go with pure interpretation, and even if you disable runtime bytecode verification. It's just generally heavyweight and slow to get off the ground.
I imagine JIT compilation should help with this, as you suggest.
Oops, too late to edit, but I meant ahead-of-time compilation should help with this
Since Java 8, there are two ways to build a binary: the javapackager tool, and the Ant JavaFX tasks (with the OpenJDK, install the openjfx package). It'll include the JRE [~50MB], and there are pros and cons with that obviously.
jlink[1] makes it pretty easy if you're using a recent JDK.
[1] https://docs.oracle.com/javase/9/tools/jlink.htm
Which person's idea of idiomatic ?
"One can, with sufficient effort, essentially write C code in Haskell using various unsafe primitives. We would argue that this is not true to the spirit and goals of Haskell, and we have attempted in this paper to remain within the space of reasonably idiomatic Haskell. However, we have made abundant use of strictness annotations, explicit strictness, and unboxed vectors. We have, more controversially perhaps, used unsafe array subscripting in places. Are our choices reasonable?"
http://www.leafpetersen.com/leaf/publications/ifl2013/haskel...
Programs for the n-body and spectral-norm procedural benchmarks game tasks, perform kind-of the same in Haskell and Java
https://benchmarksgame-team.pages.debian.net/benchmarksgame/...
These benchmarks seem pretty good. Filterable by language, etc.
https://www.techempower.com/benchmarks/
The source code is published too (https://github.com/TechEmpower/FrameworkBenchmarks)
“Unsuitable” doesn’t mean it can’t be done. Having written a lot of business software in Java, I actually agree it’s unsuitable. The only way I’ve been able to make it bearable is by using Lombok and pcollections.
How so? Performance? Reliability? Verbosity? Which language is suitable in your opinion?
To me this kind of opinion-based... um, opinions... fly in the face of evidence. Java has been used for more than a decade to deploy business software to great success. What more evidence does one need? It'd be like arguing "COBOL is unsuitable for banking".
In the meantime, opinions have shifted on best engineering practices, and Java has naturally run the gamut of all these opinions. And because there are tons of Java systems, there's no shortage of examples of failed/bad projects one could pick on. I wonder how many languages/platforms would have fared better...
"Unsuitable" meaning it's not a great choice. Yes, it's been done a lot (whether or not you can really say "to great success" is another matter, I think).
What I mean is that I think using Java meant the company was required to spend more resources than should have been necessary to accomplish their goal.
BTW, when I say "Java", I mean the language, not the platform. Java-the-platform is very suitable to business software. Java-the-language, less so. Java OOP brings with it a ridiculous amount of incidental complexity, boilerplate, and impedance mismatches. Of course you can make it work, I do it every day. I just think it's a poor choice. It's certainly not the worst choice, and the platform + available libraries is definitely a plus.
And as I mentioned in my original post, there are way to make it more suitable through various hacks (like Lombok) and libraries, but other languages are more suitable out of the box (including other JVM languages).
If you liked pcollections, you might also like https://www.vavr.io/
Not talking against Haskell or FP; The disadvantage is being hard to reason about performance. Ensuring compiler will optimize something will take more cognitive load than simply writing straightforward code.
Imagine having a map() method on an array that produces another array. In a long chained pipeline of such things, compiler may be able to elide extra allocations and generate asm very near to handwritten for loops. But the abstraction breaks when the method does I/O or has side effects - you can't reorder anything in order to elide allocations. (Well this example may not make sense in Haskell because Haskell is lazily evaluated).
However there is a limit to what compiler can do, and it might manifest in edge cases like variation in order of imports. I'd rather have straightforward code than relying on compiler optimizations.
I am not arguing "against abstractions" like some Go fanboys tell you map and filter are less efficient. It is always possible to apply same map filter to iterators/lazy streams instead of arrays and get same performance in straightforward code. But that's not same as keeping in mind what heuristics compiler uses to optimize the code.
I suppose in FP/Haskell you would structure your code differently, so that it wouldn't have side effects when mapping arrays. That way you could even parallelize it trivially.
High level languages produce a lot less code than than less optimized implementations. Difficulties with reasoning about execution/performance is the penalty you potentially have to pay.
In my experience it indeed may be hard to understand performance with Haskell. That said, it comes with excellent tooling to overcome it in most of the cases.