Add space type conversion to support Faiss cosine similarity

Signed-off-by: owenhalpert <[email protected]>

Author: owenhalpert

Diff for: src/main/java/org/opensearch/knn/index/engine/faiss/Faiss.java

@@ -138,7 +138,8 @@ public boolean supportsRemoteIndexBuild(MethodComponentContext methodComponentCo
     @Override
     public RemoteIndexParameters createRemoteIndexingParameters(KNNMethodContext knnMethodContext) {
         if (METHOD_HNSW.equals(knnMethodContext.getMethodComponentContext().getName())) {
-            return FaissHNSWMethod.createRemoteIndexingParameters(knnMethodContext);
+            FaissHNSWMethod method = (FaissHNSWMethod) METHODS.get(METHOD_HNSW);
+            return method.createRemoteIndexingParameters(knnMethodContext);
         }
         throw new IllegalArgumentException("Unsupported method for remote indexing");
     }

Diff for: src/main/java/org/opensearch/knn/index/engine/faiss/FaissHNSWMethod.java

@@ -158,10 +158,11 @@ protected Function<TrainingConfigValidationInput, TrainingConfigValidationOutput
      * @param knnMethodContext to parse
      * @return Map of parameters to be used as "index_parameters"
      */
-    public static RemoteIndexParameters createRemoteIndexingParameters(KNNMethodContext knnMethodContext) {
+    public RemoteIndexParameters createRemoteIndexingParameters(KNNMethodContext knnMethodContext) {
         RemoteFaissHNSWIndexParameters.RemoteFaissHNSWIndexParametersBuilder<?, ?> builder = RemoteFaissHNSWIndexParameters.builder();
         builder.algorithm(METHOD_HNSW);
-        builder.spaceType(knnMethodContext.getSpaceType().getValue());
+        SpaceType spaceType = convertUserToMethodSpaceType(knnMethodContext.getSpaceType());
+        builder.spaceType(spaceType.getValue());
 
         MethodComponentContext methodComponentContext = knnMethodContext.getMethodComponentContext();
         Map<String, Object> methodParams = methodComponentContext.getParameters();

Diff for: src/test/java/org/opensearch/knn/index/engine/KNNEngineTests.java

@@ -125,7 +125,8 @@ public void testSupportsRemoteIndexBuild() {
     }
 
     public void testCreateRemoteIndexingParameters_Success() {
-        RemoteIndexParameters result = FaissHNSWMethod.createRemoteIndexingParameters(createMockMethodContext());
+        FaissHNSWMethod method = new FaissHNSWMethod();
+        RemoteIndexParameters result = method.createRemoteIndexingParameters(createMockMethodContext());
 
         assertNotNull(result);
         assertTrue(result instanceof RemoteFaissHNSWIndexParameters);
@@ -139,6 +140,21 @@ public void testCreateRemoteIndexingParameters_Success() {
         assertEquals(14, hnswParams.getM());
     }
 
+    public void testCreateRemoteIndexingParameters_CosineSpaceType() {
+        FaissHNSWMethod method = new FaissHNSWMethod();
+        KNNMethodContext context = createMockMethodContextWithCosineSimil();
+
+        RemoteIndexParameters result = method.createRemoteIndexingParameters(context);
+
+        assertNotNull(result);
+        assertTrue(result instanceof RemoteFaissHNSWIndexParameters);
+
+        RemoteFaissHNSWIndexParameters hnswParams = (RemoteFaissHNSWIndexParameters) result;
+
+        // Test that cosine space type is converted to inner product space type for Faiss
+        assertEquals(SpaceType.INNER_PRODUCT.getValue(), hnswParams.getSpaceType());
+    }
+
     public static KNNMethodContext createFaissIVFMethodContext() {
         MethodComponentContext encoder = new MethodComponentContext(ENCODER_SQ, Map.of());
         Map<String, Object> encoderMap = Map.of(METHOD_ENCODER_PARAMETER, encoder);
@@ -178,4 +194,20 @@ public static KNNMethodContext createMockMethodContext() {
         return new KNNMethodContext(KNNEngine.FAISS, SpaceType.L2, methodComponentContext);
     }
 
+    public static KNNMethodContext createMockMethodContextWithCosineSimil() {
+        MethodComponentContext encoder = new MethodComponentContext(KNNConstants.ENCODER_FLAT, Map.of());
+        Map<String, Object> parameters = Map.of(
+            KNNRemoteConstants.METHOD_PARAMETER_EF_SEARCH,
+            89,
+            KNNRemoteConstants.METHOD_PARAMETER_EF_CONSTRUCTION,
+            94,
+            KNNRemoteConstants.METHOD_PARAMETER_M,
+            14,
+            METHOD_PARAMETER_ENCODER,
+            encoder
+        );
+        MethodComponentContext methodComponentContext = new MethodComponentContext(KNNConstants.METHOD_HNSW, parameters);
+        return new KNNMethodContext(KNNEngine.FAISS, SpaceType.COSINESIMIL, methodComponentContext);
+    }
+
 }