Old problem with performance

[Weed]

(Has started here:
http://www.digitalmars.com/webnews/newsgroups.php?art_group=digitalmars.D&article_id=81359)

To me still does not give rest performance of classes (in comparison
with C++ or with D structs)

I still think that it is a serious problem.

Colleagues from our national D forum have asked to show it and I have
written simple examples on D. I want to share with you too them.

On my computer the code with structure (i.e. object by value) runs in 6
times faster than a code with a class:

$ time ./struct

real    0m8.515s
user    0m7.796s
sys     0m0.016s
$ time ./class

real    0m52.185s
user    0m40.543s
sys     0m0.076s

The code on C++ is also approximately in 6 times faster a code with
classes on D. (I do not give an example on C++ because classes on C++
work just as structures in D.)

I think with it it is necessary to do something.


Examples code:

//========================
struct C {
    int i;
    real[5] unused; // to prevent returning this object in registers

    C opAdd( C src ) {
        C ret;
        ret.i = i + src.i;
        return ret;
    }
}

int main() {
    C c1;
    C c2;

    // initialise i by "random" value to prevent compile-time calculation
    c1.i = cast(int)&c1;
    c2.i = 0;

    for(int i = 0; i < 50_000_000; ++i)
        c2 = c1 + c1 + c1;

    return c2.i;
}

//========================

class C {
    int i;
    real[5] unused; // to prevent returning this object in registers

    C opAdd( C src ) {
        auto ret = new C;
        ret.i = i + src.i;
        return ret;
    }
}

int main() {
    auto c1 = new C;
    auto c2 = new C;

    // initialise i by "random" value to prevent compile-time calculation
    c1.i = cast(int)&c1;
    c2.i = 0;

    for(int i = 0; i < 50_000_000; ++i)
        c2 = c1 + c1 + c1;

    return c2.i;
}
//========================