Vector API factories

[Graves, Ian L]

Hi Paul,

I love it!

I think you're right that it makes a lot of sense to offload instantiation routines to species and make them semi-concrete by element type.  This solves the issue of our element types being too unconstrained.  This approach lets us fix the instantiatable-element-types by exposing allowed ones through this semi-concrete species.  I think it also makes sense to refactor the vector construction methods to the Species class because instantiation is unique per-species and not per-vector.  That's a good play.



> Also i am wondering about the horizontal reductions now returning a Vector.
> I can see why you did this, we really don’t want the primitive boxes being
> exposed and you can easily reuse the result in further calculations.
> 
> This works well for the fixed sized small vectors but what if we have different
> kinds of shape that signify a larger size?
> 
> An alternative is to move those reductions into the semi-concrete species. If
> there is a method to construct a new vector with an element at the first
> position then i bet the JIT can optimize to avoid register shuffling.
> 

Reductions are somewhat sensitive to species.  I can see how some operations that are more amenable to floating point (div, etc) would be better served to be placed in a more precise location.  Right now I think you're right that it makes sense to limit this placement to species and not Vector.

Would species form the basis of a future templated feature-set of Vector that could be dropped in?  Something that could come out of the enhanced generics work in Valhalla?

--Ian