Re: Should we separate Panama FFM and Vector classes in Lucene?

Hi,

we can't backport this to 10.x because it is Java 21 only so we can't 
have any memory segments in public APIs. The plan is already to release 
a Lucene 11 at some point before end of year!

Uwe

Am 16.10.2025 um 00:06 schrieb Kaival Parikh:
> Thanks Uwe and Trevor,
>
>     No public API is allowed to have any internal Vector API
>     signatures in public API
>
>
> I agree, that's what I aimed for in the PR, keeping all incubating 
> stuff in internal APIs..
>
>     Agree on waiting for Lucene 11, otherwise it may become very
>     difficult to backport any related features into 10.x.
>
>
> To unblock related features in 10.x, can we backport this change 
> /partially/ by cherry-picking stuff internal to Lucene (i.e. 
> VectorUtilSupport), and just exclude public changes (i.e. the new 
> signatures in VectorUtil)?
>
> I really feel making MemorySegment-based vector scoring a first-class 
> API in Lucene could open up some interesting features..
>
> But yes, it would be easier overall with Lucene 11, do we have a 
> timeline for it?
>
> - Kaival
>
>
> On Mon, Oct 13, 2025 at 12:14 PM Trevor McCulloch 
> <[email protected]> wrote:
>
>     Agree on waiting for Lucene 11, otherwise it may become very
>     difficult to backport any related features into 10.x.
>
>     On Sat, Oct 11, 2025 at 5:58 PM Uwe Schindler <[email protected]> wrote:
>
>         Hi,
>
>         hi, I am on travel at the moment till end of October and won't
>         be able to look into this. Basically we can move some parts of
>         the MemorySegment supporting code to main sourceSet, but I
>         don't want to touch that code too much. The nmost important
>         thing si: No public API is allowed to have any internal Vector
>         API signatures in public API (we don't have a check fo this),
>         so we'd need to closely look at it. The reason why some of the
>         code is in the java 25 sourceset is exactly because of this.
>         E.g. the MemorySegment-based scoring.
>
>         In the future we may add more MemorySegment based APIs into
>         core (and remove all ByteBuffers, too), but this is some
>         approach I wanted to look at after we have released Lucene 11.
>
>         Uwe
>
>         Am 09.10.2025 um 23:57 schrieb Kaival Parikh:
>>         For vector search in Lucene, functionality for memory access
>>         (on/off-heap -- using Panama FFM) and vectorization (using
>>         the Vector API -- jdk.incubator.vector) is tightly coupled
>>         (see |PanamaVectorUtilSupport|
>>         <https://github.com/apache/lucene/blob/602bfbd9af0ee9027de45c1572527eee6b073841/lucene/core/src/java25/org/apache/lucene/internal/vectorization/PanamaVectorUtilSupport.java#L57>|).
>>         This made sense when it was originally added, because Panama
>>         FFM was in preview + Vector API was incubating.|
>>         |
>>         |
>>         |However, since Panama FFM was finalized in JDK22
>>         (|https://openjdk.org/jeps/454|), I wonder if we should
>>         decouple it from vectorization now?|
>>         |This would mean exposing (and supporting!) top-level
>>         on/off-heap vector similarity functions from all
>>         VectorUtilSupport
>>         <https://github.com/apache/lucene/blob/8f68736e75609d13053420450ad451e52cba107d/lucene/core/src/java/org/apache/lucene/internal/vectorization/VectorUtilSupport.java#L25> implementations
>>         (with Lucene providing one non-vectorized
>>         <https://github.com/apache/lucene/blob/8f68736e75609d13053420450ad451e52cba107d/lucene/core/src/java/org/apache/lucene/internal/vectorization/DefaultVectorUtilSupport.java#L26>
>>         and another Vector API powered vectorized
>>         <https://github.com/apache/lucene/blob/8f68736e75609d13053420450ad451e52cba107d/lucene/core/src/java25/org/apache/lucene/internal/vectorization/PanamaVectorUtilSupport.java#L57> implementation),
>>         and only scoping non-finalized (i.e. incubating Vector API
>>         related) functionality in the MR-JAR (i.e. java25/
>>         <https://github.com/apache/lucene/tree/main/lucene/core/src/java25>)|
>>         |
>>         |
>>         |Although not a huge motivation, this would allow users that
>>         do not use vectorization to score vectors off-heap.|
>>         |The main benefit could be cleaner separation of
>>         functionality in the long term, also making it easier to
>>         write new ||VectorUtilSupport
>>         <https://github.com/apache/lucene/blob/8f68736e75609d13053420450ad451e52cba107d/lucene/core/src/java/org/apache/lucene/internal/vectorization/VectorUtilSupport.java#L25> implementations
>>         that primarily work with MemorySegment APIs (for example a
>>         native implementation in #
>>         <https://github.com/apache/lucene/pull/13572>|13572
>>         <https://github.com/apache/lucene/pull/13572>|)|
>>
>>         Issue: https://github.com/apache/lucene/issues/15284
>>         PR: https://github.com/apache/lucene/pull/15285
>>
>>         - Kaival
>
>         -- 
>         Uwe Schindler
>         Achterdiek 19, D-28357 Bremen
>         https://www.thetaphi.de
>         eMail:[email protected]
>
-- 
Uwe Schindler
Achterdiek 19, D-28357 Bremen
https://www.thetaphi.de
eMail:[email protected]