[Mono-dev] Incoming changes to Mono.Simd

[Rodrigo Kumpera]

After some discussions with Mark we decided to do a few changes to Mono.Simd
and
it would be really nice to have some feedback from everyone on them.

One of the motivation is that the current C# of Mono.Simd is not endianess
safe and doesn't
work as expected on platforms such as ppc. The other is to advance the
quality of the API.

The first change is to remove byte oriented methods from all vector types
that don't work on byte quantities.

Right now the only method is ExtractByteMask which is mostly used together
with compare ops and will be replaced
 with proper operator overloads.

The second change is actually a clarification, Mono.Simd have some arch
dependent methods such as casting between
vector types that are endian unsafe. The alternative would be to define
those methods to have little-endian semantics
and, latter on, when we add support to a big-endian arch revert this
decision.

The last one is a call if extension methods should be used or not.
Extensions methods will make coding with vector
types quite a bit simpler as a lot less typing will be needed. For example,
"Vector8us.AddWithSaturation (a, b)" would
become "a.AddWithSaturation (b)". Right now we already expose some extension
methods for interoperability with arrays.

There are two issues with extension methods, first that it requires C# 3.0
and .NET 3.5 if you want your code to compile for it.
AFAIK this is no big deal as those methods would still be available under C#
2.0. The second issue is a limitation of the C# language,
which require extension methods to be defined of sealed classes. This would
mean that code written against mono 2.2 version
of Mono.Simd might not compiler with newer versions.

Keeping both versions of the methods is an option as well, but I'm not very
keen on the extra bloat imposed. Either way, I would
love to rear feedback from people evaluating or using Mono.Simd.


Cheers,
Rodrigo
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