std.variant benchmark

[jerro]

On Sunday, 29 July 2012 at 20:24:42 UTC, Dmitry Olshansky wrote:
> On 30-Jul-12 00:11, Dmitry Olshansky wrote:
>> I've found something far more evil:
>>
>> @property bool convertsTo(T)() const
>>     {
>>         TypeInfo info = typeid(T);
>>         return fptr(OpID.testConversion, null, &info) == 0;
>>     }
>>
>> Okay... now let me pull off another piece of rag:
>>
>> private VariantN opArithmetic(T, string op)(T other)
>>     {
>>         VariantN result;
>>         static if (is(T == VariantN))
>>         {
>>            /*if (convertsTo!(uint) && other.convertsTo!(uint))
>>                 result = mixin("get!(uint) " ~ op ~ " 
>> other.get!(uint)");
>>             else*/ if (convertsTo!(int) && 
>> other.convertsTo!(int))
>>                 result = mixin("get!(int) " ~ op ~ " 
>> other.get!(int)");
> ...
> Apparently I'm spot on.
> Just commenting one extra branch of this horror movie
> gives interesting change:
>
> 2779us
> 2667us
> 3153762us
>
> After:
>
> 2319us
> 2523us
> 288581us
>
> Aye, 10x :o)

I profiled it and found out much of the time is spent inside 
TypeInfo.opEquals being called from tryPutting. So I tried 
replacing "!= typeid" in tryPutting with "!is typeid". That 
brought the time from 2.8 s down to 0.12 on my machine. I don't 
know if that is the proper solution, since I don't know if typeid 
can ever return two TypeInfo objects that aren't the same but are 
equal (I haven't used typeid and TypeInfo much before). The fib 
function here does return correct result after doing that, though.