I´m playing remaking D functionalities with nogc structs, and to at least match D performance.
But in this particular case i´m unable to get near D performance.  Can someone point me out what i´m doing wrong, or if there is some magic behind the curtains on D strings?

https://dpaste.dzfl.pl/1c981fdc71ac

Dne 5.9.2016 v 13:11 Patric via Digitalmars-d-learn napsal(a):

> I´m playing remaking D functionalities with nogc structs, and to at least match D performance.
> But in this particular case i´m unable to get near D performance.  Can someone point me out what i´m doing wrong, or if there is some magic behind the curtains on D strings?
>
> https://dpaste.dzfl.pl/1c981fdc71ac

One of reason could be GC, because I belive in D string it reuse memory, but in your case you always do malloc

Dne 5.9.2016 v 13:17 Daniel Kozak napsal(a):

> Dne 5.9.2016 v 13:11 Patric via Digitalmars-d-learn napsal(a):
>
>> I´m playing remaking D functionalities with nogc structs, and to at least match D performance.
>> But in this particular case i´m unable to get near D performance.  Can someone point me out what i´m doing wrong, or if there is some magic behind the curtains on D strings?
>>
>> https://dpaste.dzfl.pl/1c981fdc71ac
>
> One of reason could be GC, because I belive in D string it reuse memory, but in your case you always do malloc
>

BTW on my pc your Custom String is faster than D string

On 05/09/2016 11:11 PM, Patric wrote:
> I´m playing remaking D functionalities with nogc structs, and to at
> least match D performance.
> But in this particular case i´m unable to get near D performance.  Can
> someone point me out what i´m doing wrong, or if there is some magic
> behind the curtains on D strings?
>
> https://dpaste.dzfl.pl/1c981fdc71ac

Ok lots of bad assumptions in there so lets declare what they should be:

1. D supports three string types, string, wstring and dstring with the character types of char, wchar and dchar.
   Strings themselves have no special behavior in the compiler as they are arrays.
2. Types such as char are fixed in size, no point multiplying when its a constant 1.
3. A D string is length then pointer.

Ok, now on to implementation do not use StopWatch for benchmarking. Use benchmark[0]. This will execute the benchmark many times which removes one off errors.

Don't directly call malloc, it will never be free'd in this case.
``new char(length)`` would be better as it will automatically be handled by the GC.
You'll also want to reserve a block of memory to remove allocation from the cost as much as possible (after all you're not measuring that are you?). Don't forget to disable the GC as well so it doesn't try to collect during the tests.

[0] https://dlang.org/phobos/std_datetime.html#.benchmark
[1] http://dlang.org/spec/type.html
[2] http://dlang.org/spec/abi.html
[3] https://github.com/dlang/druntime/blob/master/src/object.d#L41

On Monday, 5 September 2016 at 11:11:23 UTC, Patric wrote:
> I´m playing remaking D functionalities with nogc structs, and to at least match D performance.
> But in this particular case i´m unable to get near D performance.
>  Can someone point me out what i´m doing wrong, or if there is some magic behind the curtains on D strings?
>
> https://dpaste.dzfl.pl/1c981fdc71ac

    string s;
    string a = "testing";
    string b = "another";
    foreach(_ ; 0..max){
	s = a ~ b;
    }

Potentially this makes no allocation at all. "testing" and "another" will be in readonly memory, "a ~ b" will be constant-folded, and s will get assigned the same slice every-time.

Now replace it with std::string in C++ and count the number of malloc ;)

Dne 5.9.2016 v 13:20 rikki cattermole via Digitalmars-d-learn napsal(a):
> ...
> Don't forget to disable the GC as well so it doesn't try to collect during the tests.
>
This is not true, in many cases it will hurt performance a lot

On Monday, 5 September 2016 at 11:20:08 UTC, rikki cattermole wrote:
> On 05/09/2016 11:11 PM, Patric wrote:
>> I´m playing remaking D functionalities with nogc structs, and to at
>> least match D performance.
>> But in this particular case i´m unable to get near D performance.  Can
>> someone point me out what i´m doing wrong, or if there is some magic
>> behind the curtains on D strings?
>>
>> https://dpaste.dzfl.pl/1c981fdc71ac
>
> Ok lots of bad assumptions in there so lets declare what they should be:
>
> 1. D supports three string types, string, wstring and dstring with the character types of char, wchar and dchar.
>    Strings themselves have no special behavior in the compiler as they are arrays.
> 2. Types such as char are fixed in size, no point multiplying when its a constant 1.
> 3. A D string is length then pointer.
>
> Ok, now on to implementation do not use StopWatch for benchmarking. Use benchmark[0]. This will execute the benchmark many times which removes one off errors.
>
> Don't directly call malloc, it will never be free'd in this case.
> ``new char(length)`` would be better as it will automatically be handled by the GC.
> You'll also want to reserve a block of memory to remove allocation from the cost as much as possible (after all you're not measuring that are you?). Don't forget to disable the GC as well so it doesn't try to collect during the tests.
>
> [0] https://dlang.org/phobos/std_datetime.html#.benchmark
> [1] http://dlang.org/spec/type.html
> [2] http://dlang.org/spec/abi.html
> [3] https://github.com/dlang/druntime/blob/master/src/object.d#L41

I´m aware of 1, and 2.

I look one million times on datetime and did´nt see the benchmark, thanks xD

My intention is to not use gc at all, so no "new" for me.
Yes the optimal case will be reserve the memory beforehand, but i´m benchmarking the opBinary.

So now a bit better example :)
https://dpaste.dzfl.pl/b9356f57a8c8


Daniel Kozak:
Ok, now it gets a bit weird.

On DPaste it shows:
14 ms and 343 μs - DString
3 ms and 928 μs - CustomString

And on my PC (with dub release mode) :

7 ms, 885 μs, and 9 hnsecs - DString
18 ms, 740 μs, and 8 hnsecs - CustomString

(!!!)

Dne 5.9.2016 v 13:45 Patric via Digitalmars-d-learn napsal(a):
> On Monday, 5 September 2016 at 11:20:08 UTC, rikki cattermole wrote:
>> On 05/09/2016 11:11 PM, Patric wrote:
>>> I´m playing remaking D functionalities with nogc structs, and to at
>>> least match D performance.
>>> But in this particular case i´m unable to get near D performance.  Can
>>> someone point me out what i´m doing wrong, or if there is some magic
>>> behind the curtains on D strings?
>>>
>>> https://dpaste.dzfl.pl/1c981fdc71ac
>>
>> Ok lots of bad assumptions in there so lets declare what they should be:
>>
>> 1. D supports three string types, string, wstring and dstring with the character types of char, wchar and dchar.
>>    Strings themselves have no special behavior in the compiler as they are arrays.
>> 2. Types such as char are fixed in size, no point multiplying when its a constant 1.
>> 3. A D string is length then pointer.
>>
>> Ok, now on to implementation do not use StopWatch for benchmarking. Use benchmark[0]. This will execute the benchmark many times which removes one off errors.
>>
>> Don't directly call malloc, it will never be free'd in this case.
>> ``new char(length)`` would be better as it will automatically be handled by the GC.
>> You'll also want to reserve a block of memory to remove allocation from the cost as much as possible (after all you're not measuring that are you?). Don't forget to disable the GC as well so it doesn't try to collect during the tests.
>>
>> [0] https://dlang.org/phobos/std_datetime.html#.benchmark
>> [1] http://dlang.org/spec/type.html
>> [2] http://dlang.org/spec/abi.html
>> [3] https://github.com/dlang/druntime/blob/master/src/object.d#L41
>
> I´m aware of 1, and 2.
>
> I look one million times on datetime and did´nt see the benchmark, thanks xD
>
> My intention is to not use gc at all, so no "new" for me.
> Yes the optimal case will be reserve the memory beforehand, but i´m benchmarking the opBinary.
>
> So now a bit better example :)
> https://dpaste.dzfl.pl/b9356f57a8c8
>
>
> Daniel Kozak:
> Ok, now it gets a bit weird.
>
> On DPaste it shows:
> 14 ms and 343 μs - DString
> 3 ms and 928 μs - CustomString
>
> And on my PC (with dub release mode) :
>
> 7 ms, 885 μs, and 9 hnsecs - DString
> 18 ms, 740 μs, and 8 hnsecs - CustomString
>
> (!!!)
Do you have windows or linux? Which version of dmd you have?

On 05/09/2016 11:45 PM, Patric wrote:
> On Monday, 5 September 2016 at 11:20:08 UTC, rikki cattermole wrote:
>> On 05/09/2016 11:11 PM, Patric wrote:
>>> I´m playing remaking D functionalities with nogc structs, and to at
>>> least match D performance.
>>> But in this particular case i´m unable to get near D performance.  Can
>>> someone point me out what i´m doing wrong, or if there is some magic
>>> behind the curtains on D strings?
>>>
>>> https://dpaste.dzfl.pl/1c981fdc71ac
>>
>> Ok lots of bad assumptions in there so lets declare what they should be:
>>
>> 1. D supports three string types, string, wstring and dstring with the
>> character types of char, wchar and dchar.
>>    Strings themselves have no special behavior in the compiler as they
>> are arrays.
>> 2. Types such as char are fixed in size, no point multiplying when its
>> a constant 1.
>> 3. A D string is length then pointer.
>>
>> Ok, now on to implementation do not use StopWatch for benchmarking.
>> Use benchmark[0]. This will execute the benchmark many times which
>> removes one off errors.
>>
>> Don't directly call malloc, it will never be free'd in this case.
>> ``new char(length)`` would be better as it will automatically be
>> handled by the GC.
>> You'll also want to reserve a block of memory to remove allocation
>> from the cost as much as possible (after all you're not measuring that
>> are you?). Don't forget to disable the GC as well so it doesn't try to
>> collect during the tests.
>>
>> [0] https://dlang.org/phobos/std_datetime.html#.benchmark
>> [1] http://dlang.org/spec/type.html
>> [2] http://dlang.org/spec/abi.html
>> [3] https://github.com/dlang/druntime/blob/master/src/object.d#L41
>
> I´m aware of 1, and 2.
>
> I look one million times on datetime and did´nt see the benchmark,
> thanks xD
>
> My intention is to not use gc at all, so no "new" for me.
> Yes the optimal case will be reserve the memory beforehand, but i´m
> benchmarking the opBinary.
>
> So now a bit better example :)
> https://dpaste.dzfl.pl/b9356f57a8c8
>
>
> Daniel Kozak:
> Ok, now it gets a bit weird.
>
> On DPaste it shows:
> 14 ms and 343 μs - DString
> 3 ms and 928 μs - CustomString
>
> And on my PC (with dub release mode) :
>
> 7 ms, 885 μs, and 9 hnsecs - DString
> 18 ms, 740 μs, and 8 hnsecs - CustomString
>
> (!!!)

Be a bit careful there, when a struct is moved around its destructor will be called. This is why I suggested you to use the GC to allocate memory or else ouch.

So you'll find very quickly that you will be having segfaults since you will be doing use after free.

Oh and you'll want to turn that into a slice at some point ``char[] str = ptr[0 .. length];``.

On Monday, 5 September 2016 at 11:53:12 UTC, Daniel Kozak wrote:
> Do you have windows or linux? Which version of dmd you have?

Now on my job pc:
DMD32 D Compiler v2.071.0-b2

In home i have 64 last version, and with my first version it shows the DString faster than my custom.