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.
>
