[Vector API] Why to talk about lanes, shapes and species in the API doc?

[Adrian Trapletti]

Hi,

In this context, maybe interesting
https://github.com/luhenry/netlib/blob/master/blas/src/main/java/dev/ludovic/netlib/blas/VectorBLAS.java
that is a BLAS implementation using the Vector API. Performance is on-par
or above native libraries for Level-1 and Level-2 BLAS.

Best regards
Adrian

*Dr. Adrian Trapletti*
CEO

*Uster Metrics GmbH  *|  Steinstrasse 9b, 8610 Uster, Switzerland
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On Wed, Mar 30, 2022 at 11:25 PM <panama-dev-request at openjdk.java.net>
wrote:

> Message: 1
> Date: Wed, 30 Mar 2022 19:37:54 +0000
> From: Paul Sandoz <paul.sandoz at oracle.com>
> To: Dietmar Lippold <dietmar.lippold at mailbox.org>
> Cc: "panama-dev at openjdk.java.net" <panama-dev at openjdk.java.net>
> Subject: Re: [Vector API] Why to talk about lanes, shapes and species
>         in the API doc?
> Message-ID: <EE93DF51-34FC-4DE9-A64C-9A69F102A0D3 at oracle.com>
> Content-Type: text/plain; charset="utf-8"
>
> Hi Dietmar,
>
> I think you have misunderstood the intent of the Vector API.
>
> The Vector API uses the term vector as in vector hardware register, whose
> size is a fixed number of bits (shape), and can be viewed as a fixed-sized
> array of primitive values (species). The API is specifically designed such
> that an instance of Vector compiles down to a value in a vector register,
> and operations compile down to one or a few vector hardware instructions. I
> sometimes refer to this API as a What You See Is What You Get (WYSIWYG) API.
>
> What you desire, quite reasonably, is a higher level abstraction to
> operate over variable length arrays. The chosen parallel mechanism would be
> an implementation detail of such an abstraction. This kind of abstraction
> also makes sense for matrices or tensors. We do want to explore such APIs
> in the platform, but IMO we would first need to identify/propose
> enhancements to language so we can design the array-like API that we would
> be comfortable proposing and supporting. (Note some enhancements make come
> with Project Valhalla we likely require more.)
>
> ?
>
> Providing a link to the relevant area of the release JavaDoc (once
> available) seems reasonable. It?s not something we have generally done with
> appropriate JEPs, but I think it?s useful.
>
> Paul.
>
> > On Mar 29, 2022, at 11:41 AM, Dietmar Lippold <
> dietmar.lippold at mailbox.org> wrote:
> >
> > Hi,
> >
> > why is it necessary to talk about "lanes", "shapes" and "species" in the
> API doc?  From my point of view a Vector should be similar to an array, in
> particular it could have an arbitrary number of _elements_ (up to
> Integer.MAX_VALUE) and it should not be necessary to know something about
> the hardware (CPU or GPU).
> >
> > On the page of JEP 417 (https://openjdk.java.net/jeps/417) there is the
> code:
> >
> >  static final VectorSpecies<Float> SPECIES =
> FloatVector.SPECIES_PREFERRED;
> >
> >  void vectorComputation(float[] a, float[] b, float[] c) {
> >      int i = 0;
> >      int upperBound = SPECIES.loopBound(a.length);
> >      for (; i < upperBound; i += SPECIES.length()) {
> >          // FloatVector va, vb, vc;
> >          var va = FloatVector.fromArray(SPECIES, a, i);
> >          var vb = FloatVector.fromArray(SPECIES, b, i);
> >          var vc = va.mul(va)
> >                     .add(vb.mul(vb))
> >                     .neg();
> >          vc.intoArray(c, i);
> >      }
> >      for (; i < a.length; i++) {
> >          c[i] = (a[i] * a[i] + b[i] * b[i]) * -1.0f;
> >      }
> >  }
> >
> > It should be possible to write instead:
> >
> >  void vectorComputation(float[] a, float[] b, float[] c) {
> >      // FloatVector va, vb, vc;
> >      var va = FloatVector.fromArray(a);
> >      var vb = FloatVector.fromArray(b);
> >      var vc = va.mul(va)
> >                 .add(vb.mul(vb))
> >                 .neg();
> >      vc.intoArray(c);
> >  }
> >
> > To make that possible the current class Vector (as well as its
> subclasses) could be converted into an inner class VectorHelp (or named
> similar) and that could handle all things of lanes, shapes and species.
> >
> > Btw: Please add a link to the API doc of the Vector package (
> https://docs.oracle.com/en/java/javase/18/docs/api/jdk.incubator.vector/jdk/incubator/vector/package-summary.html)
> to the page of the JEP 417 (https://openjdk.java.net/jeps/417).
> >
> > Dietmar
>
>