[Pixman] [PATCH] sse2: Using MMX and SSE 4.1

[Bill Spitzak]

On 06/16/2012 07:08 AM, Siarhei Siamashka wrote:

>> An alternative idea is instead of changing the algorithm across the
>> board, we could stop requiring bit exact results. The main piece of work
>> here is to change the test suite so that it will accept pixels up to
>> some maximum relative error. There is already some support for this: the
>> 'composite' test is using the 'pixel_checker_t" to do compare the pixman
>> output with perfect pixels computed in double precision.
>>
>> This latter idea is ultimately more useful because it will allow much
>> more flexibility in the kinds of SIMD instruction sets we can support.
>
> This is also a very useful test, but it effectively requires to have
> an alternative double precision implementation for all the pixman
> functionality to be verified.

I don't understand this.

The current tests are checking for equality with am image. The 
approximate results will just check for approximate equality with the 
same image. I fail to see why the image has to somehow be "more correct".