std.variant benchmark

[Gor Gyolchanyan]

On Fri, Aug 3, 2012 at 8:28 AM, jerro <a at a.com> wrote:

> 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.
>

Wow! Now that's an impressive improvement. If TypeInfo instances are unique
for every type, then we should be good to go!

-- 
Bye,
Gor Gyolchanyan.
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