Re: FP/IP and performance (in general) and Patterns... (Re: [Caml-list] Avoiding shared data)

[Oliver Bandel <oliver@first.in-berlin.de>]

On Tue, Oct 04, 2005 at 07:45:12PM -0500, Brian Hurt wrote:
[...] 
> The big advantage of FP programming IMHO is not performance, but instead 
> *correctness*.  With today's multi-gigahertz machines with multi-gigabytes 
> of memory, performance isn't as critical as it used to be.  But 
> correctness- especially automatically gaurenteed correctness on projects 
> spanning hundreds of thousands of lines of code and dozens of developers 
> maintained over decades of time- starts becoming critical.

Yes, I agree on this.
I get daily messages from an buglist-mailinglist, where most often
things like typical memory-exploits are the reason of why a system
or a process can be exploited.

So, the typical "out of bounds" and "format string" problems
are typical security risks.
(Btw: is OCaml's format-string stuff from the Printf-module save in
this respect?!)


> I'd quite 
> happily trade off 10% performance for correctness, or even 50% 
> performance.

Well, if the code with correctness is nearly as fast as the code without,
it would be best.


> 
> FP is a huge gain in correctness, because it allows me to *control 
> mutability*.  If I pass a mutable data structure to a block of code there 
> is an instant implicit contract between the caller and the callee on how 
> (or wether) to modify the mutable data structure.  It doesn't matter what 
> the contract is- wether it's to not modify the structure at all, to allow 
> optional modification (either unlimited or only in certain ways), or to 
> require certain modifications- a dependency between the two different 
> peices of code exists.  And this dependency, this contract, is probably 
> undocumented and always unchecked by the compiler, which means it's a 
> maintaince nightmare waiting to happen.  One peice of code gets modified 
> to violate the contract, perhaps even unknowingly, or perhaps due to some 
> changing requirement, and untouched code thousands of lines away suddenly 
> breaks.


Yes, this is a very well description of the FP-advantages.
Nevertheless, if a solution is too slow, it hinders
people from adopting FPLs for their programmig, and
software remains unsecure/unsafe, because they again and again
will choose the unsafe langauges... :(


Ciao,
   Oliver