# [Mono-dev] Mono.SIMD

Alan McGovern alan.mcgovern at gmail.com
Mon Feb 23 05:41:49 EST 2009

```Hey,

The big issue you're having is that you haven't implemented a SIMD algorithm
;) I spent 15 mins 'optimising' your code and came up with this. Notice that
I made everything a SIMD operation. There is no scalar code in the method
anymore. This tripled performance as compared to the non-SIMD version. On my
machine:

-FLOAT 00:00:00.3888930 Color
-SIMD   00:00:00.1266820 Mono.Simd.Vector4f

You'd want to double check the result just in case I made a mistake with my
alterations.

Alan.

{
Vector4f finv_WH = new Vector4f (1.0f / (w*h), 1.0f / (w*h),
1.0f / (w*h), 1.0f / (w*h));
Vector4f ret = new Vector4f();

Vector4f a = new Vector4f(0.0f, 0.0f, 1.0f, 1.0f);
a += new Vector4f(0.0f, 1.0f, 0.0f, 1.0f);
a += new Vector4f(1.0f, 0.0f, 0.0f, 1.0f);
a += new Vector4f(0.5f, 0.5f, 1.0f, 1.0f);

//Process operator
Vector4f yVec = new Vector4f (h, h, 0, 0);
Vector4f yDiff = new Vector4f (-1, -1, 1, 1);
for (int y=0; y<h; y++)
{
Vector4f factor = yVec * finv_WH;
yVec += yDiff;

Vector4f xVec = new Vector4f (w, 0, w, 0);
Vector4f xDiff = new Vector4f (-1, 1, -1, 1);
for (int x=0; x<w; x++)
{
ret += (a * xVec * factor);
xVec += xDiff;
}
}
return ret;
}

On Fri, Feb 20, 2009 at 8:12 AM, Johann_fxgen <jnadalutti at gmail.com> wrote:

>
> I have done some performance tests of SIMD under windows.
>
> Results tests in ms:
> In MS C         235   (Visual Studio Release Mode With SIMD)
> In MS C         360   (Visual Studio Release Mode With 4D Float)
> In Mono C#    453   (With Mono SIMD)
> In Mono C#    562   (With Mono 4D Float)
> In MS C#       609   (Visual Studio With 4D Float)
> In MS C         672   (Visual Studio Debug Mode)
>
> I'm just surprise by difference between C SIMD and mono SIMD version.
>
> Is Mono.SIMD under linux speeder than under windows ?
>
> Johann.
>
> My mono code for test:
>
>        using Mono.Simd;
>        using System;
>        using Mono;
>
>        public struct Color
>        {
>                public float r,g,b,a;
>        };
>
>        public class TestMonoSIMD
>        {
>                public  Color m_pixels;
>                const int w = 4096;
>                const int h = 4096;
>
>                public static void Main ()
>                {
>                        //Debug
>                        Console.WriteLine("AccelMode: {0}",
> Mono.Simd.SimdRuntime.AccelMode );
>
>                        //Without SIMD
>                        DateTime start1 = DateTime.Now;
>                        TimeSpan ts1 = DateTime.Now - start1;
>                        Console.WriteLine("-FLOAT {0} {1}", ts1, ret1);
>
>                        //With SIMD
>                        DateTime start2 = DateTime.Now;
>                        TimeSpan ts2 = DateTime.Now - start2;
>                        Console.WriteLine("-SIMD  {0} {1}", ts2, ret2);
>                }
>
>                {
>                        float finv_WH = 1.0f / (float)(w*h);
>                        Color ret = new Color();
>                        ret.r=ret.g=ret.b=ret.a=0.0f;
>
>                        Color a = new Color();
>                        Color b = new Color();
>                        Color c = new Color();
>                        Color d = new Color();
>                        a.r=0.0f;       a.g=0.0f; a.b=1.0f; a.a=1.0f;
>                        b.r=0.0f;       b.g=1.0f; b.b=0.0f; b.a=1.0f;
>                        c.r=1.0f;       c.g=0.0f; c.b=0.0f; c.a=1.0f;
>                        d.r=0.5f;       d.g=0.5f; d.b=1.0f; d.a=1.0f;
>
>                        //Process operator
>                        for (int y=0; y<h; y++)
>                        {
>                                for (int x=0; x<w; x++)
>                                {
>                                        //Calc percent A,B,C,D
>                                        float pa = (float)((w-x)        *
> (h-y)) * finv_WH;
>                                        float pb = (float)((x)          *
> (h-y)) * finv_WH;
>                                        float pc = (float)((w-x)        *
> (y))   * finv_WH;
>                                        float pd = (float)((x)          *
> (y))   * finv_WH;
>
>                                        float cr= ((a.r*pa) + (b.r*pb) +
> (c.r*pc) + (d.r*pd));
>                                        float cg= ((a.g*pa) + (b.g*pb) +
> (c.g*pc) + (d.g*pd));
>                                        float cb= ((a.b*pa) + (b.b*pb) +
> (c.b*pc) + (d.b*pd));
>                                        float ca= ((a.a*pa) + (b.a*pb) +
> (c.a*pc) + (d.a*pd));
>                                        ret.r+=cr;      ret.g+=cg;
>  ret.b+=cb;      ret.a+=ca;
>                                }
>                        }
>                        return ret;
>                }
>
>                {
>                        float finv_WH = 1.0f / (float)(w*h);
>                        Vector4f ret = new Vector4f(0.0f, 0.0f, 0.0f, 0.0f);
>
>                        Vector4f a = new Vector4f(0.0f, 0.0f, 1.0f, 1.0f);
>                        Vector4f b = new Vector4f(0.0f, 1.0f, 0.0f, 1.0f);
>                        Vector4f c = new Vector4f(1.0f, 0.0f, 0.0f, 1.0f);
>                        Vector4f d = new Vector4f(0.5f, 0.5f, 1.0f, 1.0f);
>
>                        //Process operator
>                        Vector4f p = new Vector4f();
>                        Vector4f r = new Vector4f();
>                        for (int y=0; y<h; y++)
>                        {
>                                for (int x=0; x<w; x++)
>                                {
>                                        //Calc percent A,B,C,D
>                                        p.X = (float)((w-x)     * (h-y)) *
> finv_WH;
>                                        p.Y = (float)((x)               *
> (h-y)) * finv_WH;
>                                        p.Z = (float)((w-x)     * (y))   *
> finv_WH;
>                                        p.W = (float)((x)               *
> (y))   * finv_WH;
>
>                                        ret+=a*p + b*p + c*p + d*p;
>                                }
>                        }
>                        return ret;
>                }
>
>        }
>
>
> --
> View this message in context:
> http://www.nabble.com/Mono.SIMD-tp22116483p22116483.html
> Sent from the Mono - Dev mailing list archive at Nabble.com.
>
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>
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