this works ok for me with ldc compiler, gdc does not work on my arch machine so I can not do comparsion to your c++ versin (clang does not work with your c++ code)

import std.stdio : writeln;

import std.algorithm.comparison: min;

import std.algorithm.iteration: sum;

import core.time: MonoTime, Duration;

T[] sum_subranges(T)(T[] input, uint range)

{

    import std.array : appender;

    auto app = appender!(T[])();

    if (range == 0)

    {

        return app.data;

    }

    for (uint i; i < input.length; i=min(i+range, input.length))

    {

        app.put(sum(input[i..min(i+range, input.length)]));

    }

    return app.data;

}

unittest

{

    assert(sum_subranges([1,1,1], 2) == [2, 1]);

    assert(sum_subranges([1,1,1,2,3,3], 2) == [2, 3, 6]);

    assert(sum_subranges([], 2) == []);

    assert(sum_subranges([1], 2) == [1]);

    assert(sum_subranges([1], 0) == []);

}

int main()

{

    import std.range : iota, array;

    auto v = iota(0,1000000).array;

    int sum;

    MonoTime beg = MonoTime.currTime;

    for (int i=0; i < 100; i++)

        sum += cast(int)sum_subranges(v,2).length;

    MonoTime end = MonoTime.currTime;

    writeln(end-beg);

    writeln(sum);

    return sum;

}

On Sun, Aug 13, 2017 at 9:03 AM, Neia Neutuladh via Digitalmars-d-learn <digitalmars-d-learn@puremagic.com> wrote:

On Sunday, 13 August 2017 at 06:09:39 UTC, amfvcg wrote:

Hi all,
I'm solving below task:

Well, for one thing, you are preallocating in C++ code but not in D.

On my machine, your version of the code completes in 3.175 seconds. Changing it a little reduces it to 0.420s:

    T[] result = new T[input.length];
    size_t o = 0;
    for (uint i; i < input.length; i=min(i+range, input.length))
    {
        result[o] = sum(input[i..min(i+range, input.length)]);
        o++;
    }
    return result[0..o];

You can also use Appender from std.array.