std.variant benchmark

[Gor Gyolchanyan]

On Mon, Jul 30, 2012 at 6:07 AM, Andrei Alexandrescu <
SeeWebsiteForEmail at erdani.org> wrote:

> On 7/29/12 11:20 AM, Gor Gyolchanyan wrote:
>
>> On Sun, Jul 29, 2012 at 6:43 PM, Dmitry Olshansky <dmitry.olsh at gmail.com
>> <mailto:dmitry.olsh at 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
>

You're right. I'm trying to make a subject-oriented system, where there are
nodes and accessors and each accessor has access to a specific part of the
node. I must have the data stored in typeless manner and cast to the
appropriate type (depending on the accessor). This is all necessary for my
very flexible graph data structure.

-- 
Bye,
Gor Gyolchanyan.
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