Add duplicate and identity offset tests for BULK_OFFSETS

libs/native/src/test/java/org/elasticsearch/nativeaccess/jdk/JDKVectorLibraryInt7uTests.java

@@ -140,6 +140,61 @@ public void testInt7uBulkWithOffsets() {
         assertScoresEquals(expectedScores, bulkScoresSeg);
     }
 
+    // All offsets point to the same vector; every score in the result should be identical.
+    public void testInt7uBulkWithDuplicateOffsets() {
+        assumeTrue(notSupportedMsg(), supported());
+        final int dims = size;
+        final int numVecs = randomIntBetween(4, 101);
+        var vectors = new byte[numVecs][dims];
+        var vectorsSegment = arena.allocate((long) dims * numVecs);
+        for (int i = 0; i < numVecs; i++) {
+            randomBytesBetween(vectors[i], MIN_INT7_VALUE, MAX_INT7_VALUE);
+            MemorySegment.copy(vectors[i], 0, vectorsSegment, ValueLayout.JAVA_BYTE, (long) i * dims, dims);
+        }
+        int target = randomInt(numVecs - 1);
+        var offsets = new int[numVecs];
+        var offsetsSegment = arena.allocate((long) numVecs * Integer.BYTES);
+        for (int i = 0; i < numVecs; i++) {
+            offsets[i] = target;
+            offsetsSegment.setAtIndex(ValueLayout.JAVA_INT, i, target);
+        }
+        int queryOrd = randomInt(numVecs - 1);
+        float[] expectedScores = new float[numVecs];
+        scalarSimilarityBulkWithOffsets(vectors[queryOrd], vectors, offsets, expectedScores);
+
+        var nativeQuerySeg = vectorsSegment.asSlice((long) queryOrd * dims, dims);
+        var bulkScoresSeg = arena.allocate((long) numVecs * Float.BYTES);
+        similarityBulkWithOffsets(vectorsSegment, nativeQuerySeg, dims, dims, offsetsSegment, numVecs, bulkScoresSeg);
+        assertScoresEquals(expectedScores, bulkScoresSeg);
+
+        for (int i = 1; i < numVecs; i++) {
+            assertEquals(bulkScoresSeg.get(JAVA_FLOAT_UNALIGNED, 0L), bulkScoresSeg.get(JAVA_FLOAT_UNALIGNED, (long) i * Float.BYTES), 0f);
+        }
+    }
+
+    // Identity offsets (offsets[i] == i) should produce the same results as the non-offset bulk path.
+    public void testInt7uBulkWithIdentityOffsets() {
+        assumeTrue(notSupportedMsg(), supported());
+        final int dims = size;
+        final int numVecs = randomIntBetween(2, 101);
+        var vectors = new byte[numVecs][dims];
+        var vectorsSegment = arena.allocate((long) dims * numVecs);
+        var offsetsSegment = arena.allocate((long) numVecs * Integer.BYTES);
+        for (int i = 0; i < numVecs; i++) {
+            randomBytesBetween(vectors[i], MIN_INT7_VALUE, MAX_INT7_VALUE);
+            MemorySegment.copy(vectors[i], 0, vectorsSegment, ValueLayout.JAVA_BYTE, (long) i * dims, dims);
+            offsetsSegment.setAtIndex(ValueLayout.JAVA_INT, i, i);
+        }
+        int queryOrd = randomInt(numVecs - 1);
+        float[] expectedScores = new float[numVecs];
+        scalarSimilarityBulk(vectors[queryOrd], vectors, expectedScores);
+
+        var nativeQuerySeg = vectorsSegment.asSlice((long) queryOrd * dims, dims);
+        var bulkScoresSeg = arena.allocate((long) numVecs * Float.BYTES);
+        similarityBulkWithOffsets(vectorsSegment, nativeQuerySeg, dims, dims, offsetsSegment, numVecs, bulkScoresSeg);
+        assertScoresEquals(expectedScores, bulkScoresSeg);
+    }
+
     public void testInt7uBulkWithOffsetsAndPitch() {
         assumeTrue(notSupportedMsg(), supported());
         final int dims = size;