Saturating integer arithmetic

[Andrei Alexandrescu via Digitalmars-d]

On 6/26/16 9:47 AM, Manu via Digitalmars-d wrote:
> Hi people. I've been working on this colour library when I have free
> time (almost never!), and I want to work on blending/filtering
> functions, but that work is kinda blocked by saturating arithmetic
> logic.
> I started working on a saturating integer library a few times, but
> it's much a much bigger job than it appears, and I haven't had enough
> time for it. (Efficient) implementation tends to be significantly
> different for every int width and signed/unsigned. I see no use for an
> inefficient implementation used by a colour library; images tend to be
> millions of pixels, and inefficiency very quickly adds up.

See the recent thread "DbI checked integral". Saturation is a direct 
goal, and you should be able to optimize operations for each type by 
defining relatively small hooks.

> I wonder if anyone has an interest in the area and wants to have a go
> at it? It's a pretty big job.
> It should support scalars, packed vectors (ie, 4 bytes in an int), and
> SIMD vectors (wider vectors using hardware simd ops). Each step can
> gain considerable efficiency for the vector width. It's hard to write
> a useful colour blending library without the full set of these
> available.

What primitives would the vectors implement?


Andrei