std.range.zip performance

[bearophile]

I have done one more test, with a much simpler zip(). The code is now faster, but it seems there's no hope to have an acceptable performance. Maybe D needs a built-in zip as Clay.

Bye,
bearophile

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Timings, seconds, best of 3:
  #1:  1.95
  #2: 61.50
  #3:  2.25
  #4:  1.52
  #5: 15.50

Note: removing the this() the program #5 gets about 2-3 seconds faster.

-----------------------

// program #5 (D2)
import std.c.stdio: printf;

struct zip {
    int[] arr1, arr2;
    size_t i;

    static struct Element { int _0, _1; }

    this(int[] a1, int[] a2)
        in {
            assert(a1.length == a2.length);
        } body {
            arr1 = a1;
            arr2 = a2;
        }

    bool empty() {
        return i >= arr1.length;
    }

    @property Element front() {
        return Element(arr1[i], arr2[i]);
    }

    void popFront() {
        i++;
    }
}

void main() {
    auto a = [18,10,17,14,19,23,11,0,6,0,17,25,5,4,19,21,17,13,5,7,11,22,23,17,24,7,11,11,1,28];
    auto b = [9,12,1,4,1,18,11,6,5,18,24,15,26,14,24,8,17,26,23,17,3,28,27,0,9,27,0,19,13,25];
    int tot = 0;
    foreach (i; 0 .. 50_000_000)
        foreach (xy; zip(a, b))
            tot += xy._0 + xy._1;
    printf("%d\n", tot);
}

----------------------

Just loops program #5:

LCE:        mov 024h[ESP],EBX
        lea EBX,054h[ESP]
        xor EDX,EDX
        mov [EBX],EDX
        mov EAX,014h[ESP]
        lea ESI,054h[ESP]
        mov 4[EBX],EDX
        lea EDI,034h[ESP]
        mov 8[EBX],EDX
        mov 0Ch[EBX],EDX
        mov 010h[EBX],EDX
        mov EDX,018h[ESP]
        mov 058h[ESP],EDX
        mov EDX,020h[ESP]
        mov 054h[ESP],EAX
        mov EAX,01Ch[ESP]
        mov 05Ch[ESP],EAX
        mov 060h[ESP],EDX
        movsd
        movsd
        movsd
        movsd
        movsd
        mov ECX,044h[ESP]
        cmp ECX,034h[ESP]
        jae L167
L11D:       mov EBX,044h[ESP]
        mov EDX,038h[ESP]
        mov ESI,[EBX*4][EDX]
        mov EAX,034h[ESP]
        mov EDX,040h[ESP]
        mov ECX,[EBX*4][EDX]
        mov 078h[ESP],ECX
        mov EAX,03Ch[ESP]
        mov EDX,078h[ESP]
        mov 074h[ESP],ESI
        mov EAX,074h[ESP]
        mov EBX,074h[ESP]
        mov 070h[ESP],EDX
        add EBX,070h[ESP]
        add EBP,EBX
        inc dword ptr 044h[ESP]
        mov ESI,044h[ESP]
        mov 06Ch[ESP],EAX
        cmp ESI,034h[ESP]
        jb  L11D
L167:       mov EBX,024h[ESP]
        inc EBX
        cmp EBX,02FAF080h
        jb  LCE

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