double base_c( const double[] values) pure nothrow @nogc @safe
{
    double sum = 0.0;
    for (auto i = 0; i < values.length; ++i)
        sum += values[i] * values[i];
    return sum;
}

double base_d(double[] values) pure nothrow @nogc @safe
{
    double sum = 0.0;
    foreach (v; values)
        sum += v * v;
    return sum;
}

double d_with_sum(double[] values) @safe pure nothrow
{
    import std.algorithm : sum;
    double[] squares;
    squares[] = values[] * values[];
    return squares.sum;
}

double d_with_fold(double[] values) pure @safe
{
    import std.algorithm : fold;
    return values.fold!((r,v) => r + v*v)(0.0);
}

void main() @safe
{
    import std.random : uniform, Random, unpredictableSeed;
    import std.stdio : writefln, writeln;
    import std.datetime.stopwatch : StopWatch, Duration;

    double[] values;
    auto rnd = Random(unpredictableSeed);
    foreach (i; 0 .. 32_000_000)
        values ~= i; //uniform(0.0f, 10.0, rnd);

    Duration t1, t2, t3, t4;
    StopWatch sw;
    enum n = 10;//0_000;
    double r1, r2, r3, r4;
    r1 = r2 = r3 = r4 = 0;
    foreach (_; 0 .. n) {
        sw.reset();
        sw.start();
        r1 += base_c(values);
        sw.stop();
        t1 += sw.peek();

        sw.reset();
        sw.start();
        r2 += base_d(values);
        sw.stop();
        t2 += sw.peek();

        sw.reset();
        sw.start();
        r3 += d_with_sum(values);
        sw.stop();
        t3 += sw.peek();

        sw.reset();
        sw.start();
        r4 += d_with_fold(values);
        sw.stop();
        t4 += sw.peek();
    }

    // print res(rX) too for no drop calcs at all
    writefln( "t1=%-30s \tr=%-25.0f", t1/n, r1/n );
    writefln( "t2=%-30s \tr=%-25.0f", t2/n, r2/n );
    writefln( "t3=%-30s \tr=%-25.0f", t3/n, r3/n );
    writefln( "t4=%-30s \tr=%-25.0f", t4/n, r4/n );
}