[Vector] RFR: reshape, resize, rebracket, cast

[Vladimir Ivanov]

>> I have new webrev which modifies the tests to use the new methods - 
>> http://cr.openjdk.java.net/~kkharbas/vector-api/webrev-reshape_etc.01
>> Incremental webrev - 
>> http://cr.openjdk.java.net/~kkharbas/vector-api/webrev-reshape_etc.01_to_base 

One comment about the patch:

src/jdk.incubator.vector/share/classes/jdk/incubator/vector/Vector.java:

+    public <F> Vector<F> defaultReinterpret(Species<F> s) {

+        public abstract Class<?> vectorType();

Those operations shouldn't be part of public API.

Best regards,
Vladimir Ivanov


> It looks good to me and aligned with what was discussed previously.
> 
> Please, also update users:
> 
> $ egrep -r -e resize -e reshape -e rebracket -I -l 
> test/jdk/jdk/incubator/vector
> test/jdk/jdk/incubator/vector/benchmark/src/main/java/benchmark/jdk/incubator/vector/AbstractVectorBenchmark.java 
> 
> test/jdk/jdk/incubator/vector/benchmark/src/main/java/benchmark/jdk/incubator/vector/PopulationCount.java 
> 
> test/jdk/jdk/incubator/vector/benchmark/src/main/java/benchmark/jdk/incubator/vector/Rearrange.java 
> 
> test/jdk/jdk/incubator/vector/benchmark/src/main/java/benchmark/jdk/incubator/vector/SumOfUnsignedBytes.java 
> 
> test/jdk/jdk/incubator/vector/VectorHash.java
> test/jdk/jdk/incubator/vector/VectorReshapeTests.java
> test/jdk/jdk/incubator/vector/CovarOverrideTest.java
> 
>> New methods:
>>      class Vector<E> {
>>
>>          /* E x S  ->  E' x S' */
>>          /* was reshape() and rebracket() before */
>>          Vector<F> reinterpret(Species<F> s)
>>
>>          /* E x S  ->  E x S' */
>>          /* was resize() before */
>>          Vector<E> reshape(Species<E> s)
>>          /* E x S  ->  E' x S' */
>>          Vector<F> cast(Species<F> s)
>>      }
> 
> As a next step, I'd like to question the presence of `reshape`.
> 
> It seemed reasonable to keep it at the time discussion happened, but 
> based on my recent experience with the API, `reinterpret`/`cast` look 
> more than enough unless truncation/padding is forbidden on 
> `reinterpret`/`cast` and exposed through a dedicated API point (`reshape`).
> 
> There's one nice thing about `reshape`: it preserves element type, so 
> there's no need to cast result back to specialized vector type (e.g., 
> Vector<Integer> => IntVector). But `reinterpret`/`cast` suffer from that 
> and it would be nice to provide a workaround/solution.
> 
> For example, how about introducing Vector.toIntVector() et al which 
> serve as assertions about vector shapes backed by runtime checks?
> 
>    IntVector   v = ... ; // Int128Vector
>    LongSpecies s = ... ; // Long256Species
>    LongVector vl1 = (LongVector)v.cast(s);
>    LongVector = v.cast(s).toLongVector();
> 
> Should work rather well for fluent-style code.
> 
> Best regards,
> Vladimir Ivanov
> 
>>> -----Original Message-----
>>> From: Viswanathan, Sandhya
>>> Sent: Wednesday, January 16, 2019 12:33 PM
>>> To: Kharbas, Kishor <kishor.kharbas at intel.com>; panama-
>>> dev at openjdk.java.net; Brian Goetz <brian.goetz at oracle.com>; John Rose
>>> <john.r.rose at oracle.com>; Vladimir Ivanov
>>> <vladimir.x.ivanov at oracle.com>
>>> Cc: joe.darcy at oracle.com
>>> Subject: RE: [Vector] RFR: reshape, resize, rebracket, cast
>>>
>>>
>>> Adding Brian, John, Joe and Vladimir to the thread. Please do give your
>>> feedback on the patch from Kishor
>>> (http://cr.openjdk.java.net/~kkharbas/vector-api/webrev-reshape_etc)
>>> implementing the reinterpret API as suggested by Brian and Vladimir in
>>> thread https://mail.openjdk.java.net/pipermail/panama-dev/2018-
>>> December/003365.html.
>>>
>>> Best Regards,
>>> Sandhya
>>>
>>>
>>> -----Original Message-----
>>> From: panama-dev [mailto:panama-dev-bounces at openjdk.java.net] On
>>> Behalf Of Kharbas, Kishor
>>> Sent: Wednesday, January 16, 2019 12:20 AM
>>> To: panama-dev at openjdk.java.net
>>> Subject: [Vector] RFR: reshape, resize, rebracket, cast
>>>
>>> Hi,
>>> I have a patch which refactors the above methods as discussed in this 
>>> thread
>>> - https://mail.openjdk.java.net/pipermail/panama-dev/2018-
>>> December/003365.html.
>>>
>>> Please review the changes at - 
>>> http://cr.openjdk.java.net/~kkharbas/vector-
>>> api/webrev-reshape_etc
>>> Generation of intrinsics and correct vector boxing elimination have been
>>> verified. In the next patch I will add changes to jtreg tests.
>>>
>>> I wanted to bring forth one small issue(possibly) which programmers 
>>> might
>>> face with this change -
>>>
>>> We provide specialized types like IntVector, FloatVector, etc for 
>>> users to
>>> define their vectors and they would be able to write code like this with
>>> previous methods,
>>>      FloatVector float256 = SPECIES_FLOAT256.cast(int256); Here 
>>> FloatSpecies
>>> would always return FloatVector.
>>>
>>> However with this change, since cast() is defined on a vector and takes
>>> species of a generic type, it cannot return a specialized Vector like 
>>> IntVector
>>> or FloatVector. User has to explicitly cast the return vector from 
>>> Vector<T>
>>> to specialized Vector or use a generic vector of corresponding 
>>> element type.
>>> For example,
>>>      FloatVector float256 = (FloatVector)int256.cast(SPECIES_FLOAT256);
>>>    or
>>>      Vector<Float> float256 = int256.cast(SPECIES_FLOAT256);
>>>
>>> I am not sure if this is even a problem, but I thought its worth 
>>> mentioning.
>>>
>>> Thanks
>>> Kishor