Vector performance

[Marco Leise]

Am 13.01.2012, 11:37 Uhr, schrieb Iain Buclaw <ibuclaw at ubuntu.com>:

> On 13 January 2012 04:16, Marco Leise <Marco.Leise at gmx.de> wrote:
>> Am 12.01.2012, 16:40 Uhr, schrieb Iain Buclaw <ibuclaw at ubuntu.com>:
>>
>>> On 12 January 2012 08:29, Manu <turkeyman at gmail.com> wrote:
>>>>
>>>> On 12 January 2012 02:46, F i L <witte2008 at gmail.com> wrote:
>>>>>
>>>>>
>>>>> Well the idea is you can have both. You could even have a:
>>>>>
>>>>>  Vector2!(Transition!(Vector4!(Transition!float))) // headache
>>>>>  or something more practical...
>>>>>
>>>>>  Vector4!(Vector4!float) // Matrix4f
>>>>>  Vector4!(Transition!(Vector4!float)) // Smooth Matrix4f
>>>>>
>>>>> Or anything like that. I should point out that my example didn't  
>>>>> make it
>>>>> clear that a Matrix4!(Transition!float) would be pointless compared  
>>>>> to
>>>>> Transition!(Matrix4!float) unless each Transition held it's own
>>>>> iteration
>>>>> value. Example:
>>>>>
>>>>>  struct Transition(T, bool isTimer = false) {
>>>>>
>>>>>      T value, start, target;
>>>>>      alias value this;
>>>>>
>>>>>      static if (isTimer) {
>>>>>          float time, speed;
>>>>>
>>>>>          void update() {
>>>>>              time += speed;
>>>>>              value = start + ((target - start) * time);
>>>>>          }
>>>>>      }
>>>>>  }
>>>>>
>>>>> That way each channel could update on it's own time frame. There may
>>>>> even
>>>>> be a way to have each channel be it's own separate Transition type.
>>>>> Which
>>>>> could be interesting. I'm still playing with possibilities.
>>>>
>>>>
>>>>
>>>> The vector's aren't quite like that.. you can't make a hardware vector
>>>> out
>>>> of anything, only things the hardware supports: __vector(float[4]) for
>>>> instance.
>>>> You can make your own vector template that wraps those I guess if you
>>>> want
>>>> to make a matrix that way, but it sounds inefficient. When it comes to
>>>> writing the vector/matrix operations, if you're assuming generic code,
>>>> you
>>>> won't be able to make it anywhere near as good as if you write a
>>>> Matrix4x4
>>>> class.
>>>>
>>>>
>>>>>> I think that is also possible if that's what you want to do, and I  
>>>>>> see
>>>>>> no
>>>>>> reason why any of these constructs wouldn't be efficient (or
>>>>>> supported).
>>>>>> You can probably even try it out now with what Walter has already
>>>>>> done...
>>>>>
>>>>>
>>>>>
>>>>> Cool, I was unaware Walter had begun implementing SIMD operations.  
>>>>> I'll
>>>>> have to build DMD and test them out. What's the syntax like right  
>>>>> now?
>>>>
>>>>
>>>>
>>>> The syntax for the types (supporting basic arithmetic) look like
>>>> __vector(float[4]) float4vector.. Try it on the latest GDC.
>>>>
>>>
>>> This will change.  I'm uploading core.simd later which has a Vector!()
>>> template, and aliases for vfloat4, vdouble2, vint4, etc...
>>>
>>> I don't plan on implementing vector instrinsics in the same way Walter
>>> is doing it.
>>>
>>> a)  GCC already prodives it's own intrinsics
>>> b) The intrinsics I see Walter has already implemented in core.simd is
>>> restricted to x86 line of architectures.
>>>
>>>
>>> Regards
>>
>>
>> Looks like you two should discuss this. I see how Walter envisioned D to
>> have an inline assembler unlike C, which resulted in several vendor  
>> specific
>> syntaxes and how GCC has already done the bulk load of work to support  
>> SIMD
>> and multiple platforms. Naturally you don't want to redo that work to  
>> wrap
>> Walter's immature approach around the solid base in GDC.
>> Can you please have a meeting together with the LDC devs and decide on a
>> fair way for everyone to support inline ASM and SIMD intrinsics? Once  
>> there
>> is a common ground for three compilers other compilers will want to go  
>> the
>> same route and everyone is happy with source code that can be compiled  
>> by
>> every compiler.
>> I think this is a fundamental decision for a systems programming  
>> language.
>
> Who are the LDC devs? :)

:) Actually I don't know. Only heard about this "LLVM" that's supposed to  
be good at source-to-source compilation and is more of a framework than a  
single compiler. And then LDC emerged around that and I recently heard  
that 'its pretty much up to date'. Since you are working on GDC it seemed  
natural someone else must be actively maintaining LDC...
But dsource.org shows commits that are at least 2 years old. Look at the  
positive side: One less party to satisfy!