About JEP 338: Vector API

[forax at univ-mlv.fr]

> De: "Paul Sandoz" <paul.sandoz at oracle.com>
> À: "Remi Forax" <forax at univ-mlv.fr>
> Cc: "b lacombe" <b.lacombe at lug.com>, "panama-dev at openjdk.java.net'"
> <panama-dev at openjdk.java.net>
> Envoyé: Mercredi 10 Février 2021 19:11:47
> Objet: Re: About JEP 338: Vector API

> Hi Remi,

> Thanks for pointing out it can be done using serialization, and people do that,
> since that is what's currently possible. I think it's problematic and we can do
> much better.

> Paul.

It's not that awful :) 
Enjoy [ https://github.com/forax/vector-handle | https://github.com/forax/vector-handle ] 

It should perform well but i've not done any perf tests. 
And obviously, i've not implemented all the operations, only +, -, * and /, feel free to do some pull requests. 

Rémi 

>> On Feb 10, 2021, at 7:15 AM, Remi Forax < [ mailto:forax at univ-mlv.fr |
>> forax at univ-mlv.fr ] > wrote:

>> ----- Mail original -----

>>> De: "Paul Sandoz" < [ mailto:paul.sandoz at oracle.com | paul.sandoz at oracle.com ] >
>>> À: "b lacombe" < [ mailto:b.lacombe at lug.com | b.lacombe at lug.com ] >
>>> Cc: " [ mailto:panama-dev at openjdk.java.net | panama-dev at openjdk.java.net ] '" <
>>> [ mailto:panama-dev at openjdk.java.net | panama-dev at openjdk.java.net ] >
>>> Envoyé: Mardi 9 Février 2021 00:10:57
>>> Objet: Re: About JEP 338: Vector API

>>> Hi Bruno,

>>> You make a fair point about the complexity. The API is designed to be low-level
>>> and literal, making use of current language features, requiring a vector
>>> expression be built as an explicit tree (as if input to a compiler).

>>> It would be interesting to express:

>>> DoubleVector va = ...
>>> DoubleVector vb = ...
>>> DoubleVector vc = va.lanewise(vb, (double a, double b) -> -(a*b + b*b));

>>> Whereby the Vector API can reflect over the scalar code of the lambda
>>> expression. Then potentially use the same expression to operate over two
>>> arrays, the implementation of which may utilize the same expression for fixed
>>> length vectors over the variable length arrays.

>>> It is a non-trivial exercise (an understatement!) to modify the Java language
>>> and runtime in such a manner, but something like the above is what we have
>>> mused about before, and I think is a promising approach.

>> Hi Paul,
>> you don't need to modify neither the language nor the JDK, using a serializable
>> lambda should be enough.

>> A nice side effect of using hidden classes for the lambda proxies in jdk 16 is
>> that now the lambda proxy and the lambda itself are nestmate so if you have a
>> Lookup from the class that contains the lambda, you can call writeReplace on
>> the proxy which give you the SerializedLambda object which indicates the class
>> and method name of the lambda once desugared. Once you've got that info, you
>> can use ASM to extract the bytecode and do an abstract interpretation of the
>> bytecode to create the corresponding expression tree. So still some work, but
>> less than before.

>>> Paul.

>> Rémi

>>>> On Feb 5, 2021, at 6:19 AM, [ mailto:b.lacombe at lug.com |
>>>> b.lacombe at lug.com ] wrote:

>>>> About JEP 338: Vector API

>>>> A) you write :
>>>> -----
>>>> static final VectorSpecies<Float> SPECIES = FloatVector.SPECIES_256;

>>>> void vectorComputation(float[] a, float[] b, float[] c) {

>>>> for (int i = 0; i < a.length; i += SPECIES.length()) {
>>>> var m = SPECIES.indexInRange(i, a.length);
>>>> // FloatVector va, vb, vc;
>>>> var va = FloatVector.fromArray(SPECIES, a, i, m);
>>>> var vb = FloatVector.fromArray(SPECIES, b, i, m);
>>>> var vc = va.mul(va).
>>>> add(vb.mul(vb)).
>>>> neg();
>>>> vc.intoArray(c, i, m);
>>>> }
>>>> }
>>>> -----
>>>> It is very complexe source code to write a simple (a*a+b )*-1

>>>> It 'll more easy, if we can write :
>>>> FloatVector.forAll(a).mul(a).add(b).neg().toArray(c)
>>>> Where each operator (mul,add,neg) can make the convertion :
>>>> var va=>FloatVector.fromArray(SPECIES, a, i, m) ...
>>>> Of course optimisation can be done with a code like :
>>>> ----
>>>> void mul(a, ... buf){
>>>> var va = cache.get(a);
>>>> if( va==nul ){
>>>> va = FloatVector.fromArray(SPECIES, a, i, m);
>>>> cache.put(a,va);
>>>> }
>>>> //here va
>>>> .....
>>>> }
>>>> ----

>>>> 2) A another optimisation can be make by preparing data whith a "width"
>>>> operator like :
>>>> FloatVector
>>>> .width(a,b,c)
>>>> .forAll(a)
>>>> .mul(a).add(b).neg()
>>>> .toArray(c);
>>>> then source is more easy to read, and less complex
>>>> what did you think ?

>>>> 3) And if we can upgrade java grammar, a code like this for matrix :
>>>> c = FloatVector[[ a*a+b*-1 ]]
>>>> would be ecxellent (where a,b,c must be final array) and so easy ....

>>>> Cordialement

>>>> Bruno LACOMBE
>>>> Multimédia SOLUTIONS
>>>> Site Technologique de Marticot
>>>> 33610 Cestas
>>>> Tel (33) 05.56.21.51.18
>>>> Téléchargez Windex GED : Gestion Electronique de Documents
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