D outperformed by C++, what am I doing wrong?

[Daniel Kozak via Digitalmars-d-learn]

And this one is awesome :P
http://ideone.com/muehUw

On Sun, Aug 13, 2017 at 10:27 AM, Daniel Kozak <kozzi11 at gmail.com> wrote:

> this one is even faster than c++:
> http://ideone.com/TRDsOo
>
> On Sun, Aug 13, 2017 at 10:00 AM, Daniel Kozak <kozzi11 at gmail.com> wrote:
>
>> my second version on ldc takes 380ms and c++ version on same compiler
>> (clang), takes 350ms, so it seems to be almost same
>>
>> On Sun, Aug 13, 2017 at 9:51 AM, amfvcg via Digitalmars-d-learn <
>> digitalmars-d-learn at puremagic.com> wrote:
>>
>>> On Sunday, 13 August 2017 at 07:30:32 UTC, Daniel Kozak wrote:
>>>
>>>> Here is more D idiomatic way:
>>>>
>>>> import std.stdio : writeln;
>>>> import std.algorithm.comparison: min;
>>>> import std.algorithm.iteration: sum;
>>>> import core.time: MonoTime, Duration;
>>>>
>>>>
>>>> auto sum_subranges(T)(T input, uint range)
>>>> {
>>>>     import std.array : array;
>>>>     import std.range : chunks, ElementType;
>>>>     import std.algorithm : map;
>>>>
>>>>     if (range == 0)
>>>>     {
>>>>         return ElementType!(T)[].init;
>>>>     }
>>>>     return input.chunks(range).map!(sum).array;
>>>> }
>>>>
>>>> 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);
>>>>     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 9:13 AM, Daniel Kozak <kozzi11 at gmail.com>
>>>> wrote:
>>>>
>>>> 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 at puremagic.com> wrote:
>>>>>
>>>>> [...]
>>>>>>
>>>>>
>>> Thank you all for the replies. Good to know the community is alive in d
>>> :)
>>>
>>> Let's settle the playground:
>>> D  : http://ideone.com/h4fnsD
>>> C++: http://ideone.com/X1pyXG
>>>
>>> Both using GCC under the hood.
>>> C++ in 112 ms;
>>> D in :
>>> - 2.5 sec with original source;
>>> - 2.5 sec with Daniel's 1st version;
>>> - 5 sec timeout exceeded with Daniel's 2nd version;
>>> - 1.8 sec with Neia-like preallocation;
>>>
>>> So still it's not that neaty.
>>>
>>> (What's interesting C++ code generates 2KLOC of assembly, and Dlang @
>>> ldc 12KLOC - checked at godbolt).
>>>
>>> P.S. For C++ version to work under clang, the function which takes
>>> (BinaryOp) must go before the other one (my bad).
>>>
>>
>>
>
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