Vector API factories

[Paul Sandoz]

> On 17 Jul 2017, at 16:55, Graves, Ian L <ian.l.graves at intel.com> wrote:
> 
> 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.
> 

Ok. With that and separating FP and bitwise i think we have a reasonable API story.


> 
> 
>> 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?
> 

Yes, i think so. The lack of generics over primitives is steering me to keep Vector in the Vector world and species is the bridge to/from the Vector world.

Generics over values/primitives would be beneficial API-wise. Depending on the language features supported it may be possible to declare methods specific to the type parameter(s), so Vector<float> would have FP methods, where as Vector<int> would not (and vice versa for bitwise ops), thereby not requiring specific FP and bitwise interfaces.

Paul.