[GitHub] [lucene] msokolov commented on a diff in pull request #913: Lucene 10577

[GitBox <gi...@apache.org>]

msokolov commented on code in PR #913:
URL: https://github.com/apache/lucene/pull/913#discussion_r878553114


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lucene/core/src/java/org/apache/lucene/util/VectorUtil.java:
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@@ -213,4 +213,21 @@ public static void add(float[] u, float[] v) {
       u[i] += v[i];
     }
   }
+
+  public static float dotProduct(BytesRef a, int aOffset, BytesRef b, int bOffset, int len) {
+    // fixme -- move to codec? What if later we want to access the bytes some other way?
+    int total = 0;
+    for (int i = 0; i < len; i++) {
+      total += a.bytes[aOffset++] * b.bytes[bOffset++];

Review Comment:
   hm, well in the worst case (128 * 128) = 2^7*2^7 = 2^14 and we can sum lots of these in an int without any concern about overflow. I think the limit is on the dimension of the vector; I mean 2^31/2^14 = 2^17 and I don't think we would ever have a 2^17-dimensional vector. Perhaps this gives us a principled way to choose that max dimension :) I guess 2^17 = 128K.
   
   Looking at what `ByteVector.mul()` does ...



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