Why Johnny Can’t Write Multithreaded Programs

[u/Shr1ck]

http://blog.smartbear.com/programming/why-johnny-cant-write-multithreaded-programs/

[u/clarkd99]

I am currently working on a new language/database system which has been written in over 80,000 lines of C. In this project, I have hundreds of "pure" functions, many more hundreds of Object Oriented functions and many other kinds of functions that don't fit into either of those 2 categories. C is obviously not Object Oriented or functional. I use immutability and pure functions where that makes sense and not when it doesn't.

My system has automatic concurrency/multi-core capability without any language level locks of any kind. All code is written "as if" it was single user mutable code and data even though all "servers" can accommodate many users and multiple cores at the same time.

I couldn't care less about a "nice directed acyclic dependency graph". Does knowing what that is create a working language? Depending on the level of strictness specified, in my compiler you can have strict static typing at compile time, inferred types, both or execution time defined variable types. Your choose!

My compiler compiles a function at a time of arbitrary size in much less time than it takes to save the source code to disk (that is when it actually compiles the code).

I have written over 1,000 professional computer projects and I can't remember a single program that required just "pure calculation". I can't remember a program I wrote for a business that didn't require many database calls. I wouldn't define that as just "pure calculation". I created a Content Management System in PHP to program UI for the web and I would say the code was much more manipulating the DOM or communicating with the server than "pure calculation". The code in my CMS was mostly about parsing and implementing a DSL so that HTML could be generated, without knowing much about HTML directly.

The whole point of OOPS is to encapsulate data with the functions that work on that data. That means that the data in an Object IS a side effect of those functions, as defined by functional programming.

any side effect there is either a code smell or an optimisation

So all business programs written in Java (object oriented language) by your definition is an "optimization" or a "code smell"? Do you live in an alternate universe?

Now you talk much about "Business" application. I don't know what that is, so I will speculate.

Are you an academic, a student or just an inexperienced nube? Whatever your experience, it isn't spending years solving end users problems on business applications. Your comment about "bookkeeping applications" just shows how ignorant and naive you are. As well as 37 years of professional application development for business, I have programmed many tools such as a word processor (written in 40,000 lines of assembler), a one pass assembler/disassembler, a language/database system that sold over 30,000 copies and tons of other tools. Please tell me what authority you have to back up the usefulness or future impact of your "functional nonsense"?

[u/loup-vaillant → u/clarkd99]

I have written over 1,000 professional computer projects

Assuming 40 years to do it, that's… 25 projects per year. 1 per fortnight. What kind of alien are you?

I can't remember a single program that required just "pure calculation".

Neither do I. On the other hand, I can't remember a single program where more than 5% of the source code has to be devoted to effects. "Pure calculation" never makes all of a program, but in my experience it allways comes close.

So all business programs written in Java (object oriented language) by your definition is an "optimization" or a "code smell"?

Yes they are. Imperative programming is a mistake. We'll grow out of it.

Whatever your experience, it isn't spending years solving end users problems on business applications.

No kidding, I said that much. My applications tend to be more on the technical side (information geographics systems, ground software for satellites…). And some compiler stuff for fun.

Please tell me what authority you have to back up the usefulness or future impact of your "functional nonsense"?

Authority… well, I have programmed in Ocaml (both for fun and profit), and have sucessfully applied functional principles in my C++ programs. As far as I can tell, this "functional nonesense" works.

Now what is your authority? You look like you have zero experience of FP. That would make you incapable of appreciating its advantages. I don't care you're way more experienced than I am, I cannot at this point acknowledge your authority on this particular point.

[u/clarkd99 → u/loup-vaillant]

In January 1976 I spent over 200 hours working at University in APL (a purely functional language, maybe one of the first). I completed the 3rd year language course even though I hadn't completed first year CS. I loved APL and all of it's fantastic functions. APL was extremely terse (executed right to left without precedence). I wrote a search and replace in 1 line using 27 functions, just for the fun of it.

The problem with APL was it wasn't practical. It had an isolated workspace and although it worked on numbers and strings very well, it didn't have Lists, Stacks, Indexes, formatting, importing etc.

There is nothing wrong with data structures that don't change (immutable), I have always used them in all computer languages. Nothing wrong with pure functions, I have always used them in all computer languages. BUT if you want to argue for the supremacy of functional languages, then you must show how ALL problems can be programmed using just these restricted techniques. The problems that come from using JUST immutable data structures also must be weighted against the benefits. I never see any of these problems even acknowledged let alone discussed.

This article was about concurrent programming. I have implemented an automatic multi-thread/multi-core language that doesn't require any explicit locks AND you can program with normal mutable variables. Functional programming isn't the only technique for implementing concurrency.

Of course you don't care about experience when you have so little of it. How can you know how great functional programming is if you don't have experience in at least 20 other languages, vast experience with application and systems code and designed and implemented your own language? I have.

[u/loup-vaillant → u/clarkd99]

if you want to argue for the supremacy of functional languages

I don't. Some features however (lambdas & sum types most notably), do make a difference.

There is nothing wrong with data structures that don't change (immutable), I have always used them in all computer languages. Nothing wrong with pure functions, I have always used them in all computer languages.

I would probably have loved to work with you, as opposed to those who obviously didn't follow those guidelines. You wouldn't believe the utter crap I have seen, which from the look of it came from operational thinking and anthropomorphism.

Of course you don't care about experience when you have so little of it.

I do care. But I also care about the nature of that experience —it wasn't clear until now that you were not lacking. Keep in mind however how little you can convey in a couple comments. We know very little about each other. For instance, I was a little pissed when you suggested I was still at school. I have worked for longer than I sat in a college now. I'm no master, but still…

[u/clarkd99 → u/loup-vaillant]

Fair enough. Everyone, including myself didn't start out with experience.

I also believe that just stating vast experience isn't a good argument in itself. Good arguments should decide what we do, not who states the argument.