msokolov commented on code in PR #1054:
URL: https://github.com/apache/lucene/pull/1054#discussion_r949256714
##########
lucene/core/src/java/org/apache/lucene/util/VectorUtil.java:
##########
@@ -213,4 +243,48 @@ public static void add(float[] u, float[] v) {
u[i] += v[i];
}
}
+
+ /**
+ * Dot product computed over signed bytes.
+ *
+ * @param a bytes containing a vector
+ * @param b bytes containing another vector, of the same dimension
+ * @return the value of the dot product of the two vectors
+ */
+ public static float dotProduct(BytesRef a, BytesRef b) {
+ assert a.length == b.length;
+ int total = 0;
+ int aOffset = a.offset, bOffset = b.offset;
+ for (int i = 0; i < a.length; i++) {
+ total += a.bytes[aOffset++] * b.bytes[bOffset++];
+ }
+ return total;
+ }
+
+ /**
+ * Dot product score computed over signed bytes, scaled to be in [0, 1].
+ *
+ * @param a bytes containing a vector
+ * @param b bytes containing another vector, of the same dimension
+ * @return the value of the similarity function applied to the two vectors
+ */
+ public static float dotProductScore(BytesRef a, BytesRef b) {
+ // divide by 2 * 2^14 (maximum absolute value of product of 2 signed
bytes) * len
+ return (1 + dotProduct(a, b)) / (float) (a.length * (1 << 15));
+ }
+
+ /**
+ * Convert a floating point vector to an array of bytes using casting; the
vector values should be
+ * in [-128,127]
+ *
+ * @param vector a vector
+ * @return a new BytesRef containing the vector's values cast to byte.
+ */
+ public static BytesRef toBytesRef(float[] vector) {
Review Comment:
hmm, that seems costly to me. I think these VectorUtil methods should be
tuned for performance not safety, and we should find a way to move the safety
checks up to a higher-level API?
##########
lucene/core/src/java/org/apache/lucene/index/VectorEncoding.java:
##########
@@ -0,0 +1,45 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.lucene.index;
+
+/** The numeric datatype of the vector values. */
+public enum VectorEncoding {
+
+ /**
+ * Encodes vector using 8 bits of precision per sample. Use only with
DOT_PRODUCT similarity.
Review Comment:
no
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