On 7/29/12 11:20 AM, Gor Gyolchanyan wrote:

On Sun, Jul 29, 2012 at 6:43 PM, Dmitry Olshansky <dmitry.olsh@gmail.com

<mailto:dmitry.olsh@gmail.com>> wrote:
    This should be more relevant then:

    //fib.d
    import std.datetime, std.stdio, std.variant;

    auto fib(Int)()
    {
             Int a = 1, b = 1;
             for(size_t i=0; i<100; i++){
                     Int c = a + b;
                     a = b;
                     b = c;
             }
             return a;
    }

    void main()
    {
             writeln(benchmark!(fib!int, fib!long, fib!Variant)(10_000));
    }


    dmd -O -inline -release fib.d

    Output:

    [TickDuration(197), TickDuration(276), TickDuration(93370107)]

    I'm horrified. Who was working on std.variant enhancements? Please
    chime in.

    --
    Dmitry Olshansky

Thank you for demonstrating my point. :-)

I don't think he demonstrated your point (even leaving aside that the benchmark above is also flawed). I don't think there was a point, unless it was you wanted to vent and looked for a pretext - which is, by the way, entirely reasonable.

You mentioned you need "a very fast typeless storage with maximum performance and type safety." Well if it's typeless then it means you're using it for storage, not for computationally-intensive operations, as the code above does. So what you'd presumably want to test is the speed of data storage and retrieval. A loop that does a bunch of adds on Variant does not go in that direction.

Benchmarks are notoriously hard to get right. You need to think of reasonable baselines - if you want to use Variant for typeless storage, what is your vanilla implementation, the "obvious contender"? What are the primitives of which speed is important? Then you need to make sure you subtract noise from all your comparisons. Then you need to figure whether the issue is with the design or with the implementation of Variant. In the former case, maybe Variant isn't for you. In the latter, bug reports are always welcome.


Andrei