FreeLists / openbeos / [openbeos] Re: app_server: MMX/SSE help wanted

[Adi Oanca <e2joseph@xxxxxxxxxx>]

Hi,

Christian Packmann wrote:

> I've got a blur routine (3x3 matrix) for B_RGB32 bitmaps, which gives 
> following results on my Athlon XP 2100+ (1733MHz) with DDR266 memory:
>
>               Bitmap 640x480, 1200 KB    Bitmap 100x100, 9.76KB
> 	Code         MegaPixels/second          MegaPixels/second 
> C integer              33                           35
> MMX                    80                          125
> 3DNow!                110                          134

    Wow! I was sure there was at least a 2x difference.
        Thanks for these tests.

> The MMX routine is faster by virtue of processing multiple values with one 
> instruction. The 3DNow! routine adds data prefetching, so that the CPU 
> preloads the next chunk of data while the current chunk is being processed. 
> The C version could be improved slightly by using loop unrolling, which 
> both MMX and 3DNow! use; but this would give 10-20% increase at best.

	What about SSE, SSE2, SSE3? what can you tell us?
	Knowing they use 128bit registers, do they deliver a 4x performance 
gain over the CPU? These have support for floating point instructions 
isn't it?

> Similar speedups are likely for many bitmap operations which use alpha or 
> blending. In some extreme cases the improvements might be far more 
> spectacular, especially on the P4. The P4 design made many compromises in 
> the integer engine in order to achieve high clock speeds - shifts and 
> multiplies are very slow compared to other architectures (PIII, K7/8). This 
> will hurt performance of integer code using these instructions; and 
> especially in graphics processing you need shifts all the time to isolate 
> and join color components. By using SIMD you can alleviate this problem, as 
> the P4 delivers very good SIMD performance.

    I have a P4. I am curios about the results. :-P

> I'm not really a SIMD pro, but I'll gladly help with whatever I know. And I 
> already have a few suggestions about data alignment of bitmaps, which would 
> help SIMD coders a lot in writing efficient code.

	Good, let's hear them. Before that: do you want to write some code for 
Haiku project?

> I guess we should move this to interfacekit@xxxxxxxxxxxxx?

    Let's continue here, maybe others can help too.


Adi.