Re: [Caml-list] exn vs option

[Francois Berenger <berenger@riken.jp>]

I think there was an article about options versus exceptions
in the OCaml journal.

If I remember well, the exceptions were faster, but I can't
find back the exact benchmark and context of this assertion.

Regards,
F.

On 04/05/2012 07:10 AM, Julien Verlaguet wrote:
> 2 more use cases:
>
> 1) When writing a deep recursion
> Throwing an exception will directly jump to your "catch" block without
> having to unfold every return call site on the stack one by one. Which
> can be much faster if the recursion is very "deep".
>
> 2) When your exception is exceptional :-)
> If Not_found is never caught, then using exceptions is faster than
> option because you don't have to allocate to perform the "find"
> operation (the difference should be minimal though).
> Plus it makes your code more readable, you don't have to match on the
> return value of the find.
> This use case makes sense if you don't intend to catch Not_found, when
> Not_found is a bug, period.
>
> Le 4 avril 2012 13:38, John Carr <jfc@mit.edu <mailto:jfc@mit.edu>> a
> écrit :
>
>
>     When thinking about performance, consider the "try" keyword to take time
>     to execute.  A try block pushes an exception handler onto a stack and
>     pops the stack on exit.  The try block may also interfere with tail call
>     optimizations.
>
>     A loop like
>
>       for i = 0 to 10000000 do try ... done
>
>     executes "try" 10000001 times and will run much more slowly than
>
>       try for i = 0 to 10000000 do ... done
>
>     where "try" only executes once.
>
>     I use options where performance matters, in frequently executed code
>     where the amount of computation is not much more than the overhead of
>     a try...with.  For example, I have variants of List.assoc that return
>     options instead of raising exceptions.
>
>     Where performance doesn't matter, i.e. the amount of code in the block
>     is large or the block is rarely executed, I use exceptions or options
>     based on convenience.
>
>      > I benchmarked two programs, in one case the main function throw
>     an exception
>      > that is caught, in the other the function returns an option that
>     is pattern
>      > matched on.
>      >
>      > I noticed that, whether the exception is thrown or not, the
>     option version is
>      > always faster.
>      >
>      > Is there any case where it makes sense, performance wise, to use
>     exception
>      > instead of 'a option ?
>
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