[ODE] ODE and SIMD

[Rodrigo Hernandez]

ODE vectors are already dReal[4], other than that is better for the 
variables to be aligned at 16 bit
memory boundaries.

Vrej Melkonian wrote:
> Thanks, I previously had asked how SSE could be used
> on Windows platform but nobody knew, because gcc
> inserts SSE instructions.
>
> Also, I pretty sure the vectors need to be 4D.
>
>
> --- Francisco Leon <projectileman at yahoo.com> wrote:
>
>   
>> ODE uses macros widely for vector operations, so it
>> could take advantage of SIMD instructions implicity.
>>
>> Modern compilers translate macros to SIMD
>> instructions
>> by default, if you configure the project for
>> generating MMX/Pentium 3 instructions. 
>>
>> For example, you can configure MingW compiler for
>> generate machine code for Pentium3 or Athlon
>> plattforms, wich could result in fast code as the
>> compiler decides where to put SIMD instructions in
>> the
>> program.
>>
>> In my own benchmarking I've discovered that a vector
>> library that uses c++ templates (Like Blitz) is
>> often
>> faster than those which have SIMD assembler
>> instructions (Like NVEC or SIMDx86 libraries).
>>
>> So I think that it would better to leave the
>> low-level
>> optimizations to the compiler. Microsoft people are
>> wise enough for putting all necessary gadgets into
>> their C++ compiler. Just Trust in your compiler, it
>> is
>> more intelligent than You!! ;)
>>
>> One way for optimizing ODE is reducing the use of
>> linked lists, and pack structures in vectors. That
>> will helps the CPU work because it reduces cache
>> filling. 
>>
>> Also we can optimize ODE by using alternative math
>> functions for Sqrt and trigonometry functions.
>> Making
>> Sine and Cosine tables and using the GIMPACT SQRT
>> function would be helpful.
>>
>>     
>
>
>
>  
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