ConstKnnFloat16ValueSource accepts Inf/NaN float16 query vectors that its float32 twin ConstKnnFloatValueSource rejects (missing VectorUtil.checkFiniteFloat16)

Finding LFV-092Area: queries / function vector sourcesPriority: lowImpact: wrong errorNovelty: new

AI-assisted finding, confirmed by automated checks, not yet triaged by a human Lucene committer. This site files nothing upstream.

What it shows

You build a ConstKnnFloat16ValueSource from a float16 query vector that contains an infinity or NaN half and score it against a KnnFloat16VectorField with a FunctionQuery over Float16VectorSimilarityFunction. You expect the constructor to throw IllegalArgumentException, as its float32 twin ConstKnnFloatValueSource does (VectorUtil.checkFinite) and as KnnFloat16VectorQuery and KnnFloat16VectorField do for the same halves (VectorUtil.checkFiniteFloat16). Instead the constructor only null-checks the array, so with -ea scoring later fails with an AssertionError inside VectorUtil (no message for EUCLIDEAN; 'not finite: ... from <raw shorts>' for DOT_PRODUCT and MAXIMUM_INNER_PRODUCT; COSINE silently scores 0), and with -da documents score 0 through FunctionQuery's intended NaN/negative clamp or, for DOT_PRODUCT and MAXIMUM_INNER_PRODUCT with an infinite component, +Infinity.

The test shows that new ConstKnnFloat16ValueSource(new short[] {Float.floatToFloat16(Float.NaN)}) accepts a non-finite float16 query vector (TestConstKnnFloat16ValueSourceNonFinite#testNaNQueryVectorIsRejected), while its float32 twin ConstKnnFloatValueSource and KnnFloat16VectorQuery/KnnFloat16VectorField reject such vectors.

Expected vs actual

Expected: IllegalArgumentException (VectorUtil.checkFiniteFloat16). Actual: Expected exception IllegalArgumentException but no exception was thrown, the same with -ea and -da.

Files

src/org/apache/lucene/queries/function/TestConstKnnFloat16ValueSourceNonFinite.java (JUnit test)

Run it

Tested on Lucene main e1faeba08bde (2026-11-02): still reproduces.
Tested on Lucene main 645d4fe14a20 (2026-10-28): reproduced.
Recorded outcome of run 1 on Lucene main 645d4fe14a20: 1 test(s) run, 1 failed.
How to read the outcome: a failing test is the finding reproducing (the failure message states expected against actual).
Seeds: a rerun with the same seed replays the same random choices. Assertions off (-da -dsa -Dtests.asserts=false) is the production-like setting.

# Lucene checkout at the tested commit, built with: ./gradlew --no-daemon assemble   (JDK 25)
LUCENE=/path/to/lucene; V=12.0.0-SNAPSHOT
CP=$LUCENE/lucene/core/build/libs/lucene-core-$V.jar
CP=$CP:$LUCENE/lucene/codecs/build/libs/lucene-codecs-$V.jar
CP=$CP:$LUCENE/lucene/test-framework/build/libs/lucene-test-framework-$V.jar
CP=$CP:$LUCENE/lucene/queries/build/libs/lucene-queries-$V.jar
CP=$CP:randomizedtesting-runner-2.9.2.jar:junit-4.13.2.jar:hamcrest-3.0.jar   # test-framework dependencies (Maven Central)
CP=$CP:junit-platform-console-standalone-6.1.3.jar   # JUnit Platform console launcher (Maven Central)

javac -d classes -cp "$CP" $(find src -name '*.java')

# run 1: assertions on, seed DEADBEEF
java -ea -esa --add-modules jdk.incubator.vector --enable-native-access=ALL-UNNAMED -Dtests.seed=DEADBEEF \
     -cp "classes:$CP" org.junit.platform.console.ConsoleLauncher \
     execute --select-class org.apache.lucene.queries.function.TestConstKnnFloat16ValueSourceNonFinite

Gradle alternative: copy the test into the matching module's src/test/ tree of the checkout and run ./gradlew -p lucene/<module> test --tests <class> -Ptests.seed=<seed> (add -Ptests.asserts=false for a run without assertions).

Feedback

Open an issue in lucene-ai-bug-hunt. Please do not open issues or pull requests in apache/lucene about this finding unless a Lucene committer agrees it should be filed.

Snapshot of 2026-11-04. AI-assisted; not yet triaged by a human Lucene committer. Feedback: open an issue in lucene-ai-bug-hunt.