[erlang-questions] Erlang shows its slow face!

Frédéric Trottier-Hébert fred.hebert@REDACTED
Tue Nov 16 16:21:00 CET 2010

On 2010-11-16, at 09:51 AM, Evans, Matthew wrote:

> Interesting thread...I think we can all take the following from this:
> 1) Write your solution in the "Erlang way", using Erlang's strengths such as spawning parallel processes, also HIPE and NIFS where appropriate.
Spawning parallel processes is, in my opinion, a false ideal when it comes to algorithms like the ones presented here. In a micro-benchmark or in software that is oriented on doing only this task, multiprocessing might gain you points. In a loaded production system where all the processors are likely already busy, I wouldn't be surprised to see no big gain by using multiple processes, and if any, the gain would likely be very hard to predict. 

I think it's better to aim for the scaling kind of concurrency, not the speed-up kind. If you use processes for truly concurrent tasks (rather than attempting speedups of a single call), You'll benefit from concurrency on a higher level on a server than from each function individually.

This has to be pretty application specific, though.

> 2) Write your solution efficiently - true in all languages, but especially in Erlang where you could end up doing needless recursion.
> 3) Erlang isn't always the best language for all problems. Neither is C, C++, C#, Java or any other language. Choose the language, or a mix of languages, that are the best fit your problem.
> What I would like to add is that we are trying to get Erlang accepted in a very C/C++ centric development environment. Although time and time again Erlang has shown itself a superior language and development environment for our domain, there is still a big problem in people accepting it. One of the main stumbling blocks is it is perceived to be "slow". People always say "it won't be faster than a C/C++ solution", or "a language written in a VM will always be slow [rolleyes]".
> We can argue until we are blue in the face that it will be as good or better when you throw multi-cores in the mix. That there are other advantages including shorter development time, better debugging, redundancy, failure detection etc. But overcoming that initial "speed" bias is a tough sell. I'm not saying there is an answer to this, and I know that the development team is doing their best to make Erlang faster, but we mustn't forget that for many, the "perceived" slowness is one factor that prevents them developing in Erlang.

I think the speed obsession has to be remnants of an education always based on time efficiency, especially for programmers coming from the era where processors were really slow. Whether this explanation is right or not, I don't think it is easily possible to convince someone that 1. his priorities are not the right one and 2. the language he uses isn't the best choice for the priorities he has.

We should consider that the burden of proof is ours, not theirs. Any unsubstantiated claim is usually met with skepticism and possibly violence. This is completely normal and natural, in my opinion. The best way to convince someone is with irrefutable proof, which might be why the most common suggested way to get a team to accept Erlang is to provide them with an implementation or success stories. And maybe Erlang is no better than what they're using right now, in which case it would be a waste of money to train everyone to work in a new environment with little benefit in the long run.

If people still are not accepting it even after valid proofs, then all bets are off: maybe they don't feel like learning new technology, maybe they don't believe that *they* can write efficient Erlang code (and then you have to prove them they can), maybe they think it all comes down to the same anyway (project success isn't language dependent? which could be true in many cases), etc. I'm not sure much can be done except leading by example, in any case.

> /Rant over
> Matt

Fred Hébert

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