[Mono-dev] mono.simd sugestions

[Rodrigo Kumpera]

On Wed, Nov 19, 2008 at 4:23 PM, crashfourit <crashfourit at gmail.com> wrote:

>
>
> It would be nice to have the vector* have a constructor that takes in only
> one argument and fills all spots in the vector* with the same value.
> Like...
> Vector4f vector = new Vector4f(1);
>
> Second... I can really see someone doing this to use mono.simd in already
> established code base.
>
> [StructLayout( LayoutKind.Sequential, Pack = 0, Size = 16 )]
> class Vector4 {
>
>                /*
>                     some user defined vector methods.
>                     ..........
>               */
>
>                private static explicit operator Vector4f(Vector4 v){
>                        unsafe {
>                                Vector4f* p = (Vector4f*) &v;
>                                return *p;
>                        }
>                }
>
>                private static explicit operator Vector4(Vector4f v){
>                        unsafe {
>                                Vector4* p = (Vector4*) &v;
>                                return *p;
>                        }
>                }
> }
>
> Is it possible to accelerate these user defined operator overloads? Or do I
> have to resort to C# style unions?
> --
>
>

This code will be inlined and work like a charm. But I recommend coding it
in the following way to
squeeze the maximum  performance out of it:

    public static unsafe Vector4f AsVector(ref Vector4 v){
        fixed (Vector4 *f = &v) {
            return *(Vector4f*)f;
        }
    }



This will avoid the extra copy of passing the valuetype by value on stack
and will inline straight to a load from the
load/array element to a simd machine register. Pretty cool, isn't it?
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