1 files changed, 33 insertions, 0 deletions
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/MatchProduct.java b/vespajlib/src/main/java/com/yahoo/tensor/MatchProduct.java
new file mode 100644
index 00000000000..074742acee1
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+++ b/vespajlib/src/main/java/com/yahoo/tensor/MatchProduct.java
@@ -0,0 +1,33 @@
+// Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.tensor;
+
+import com.google.common.collect.ImmutableMap;
+
+import java.util.Map;
+import java.util.Set;
+
+/**
+ * Computes a <i>match product</i>, see {@link Tensor#match}
+ *
+ * @author bratseth
+ */
+class MatchProduct {
+
+    private final Set<String> dimensions;
+    private final ImmutableMap.Builder<TensorAddress, Double> cells = new ImmutableMap.Builder<>();
+
+    public MatchProduct(Tensor a, Tensor b) {
+        this.dimensions = TensorOperations.combineDimensions(a, b);
+        for (Map.Entry<TensorAddress, Double> aCell : a.cells().entrySet()) {
+            Double sameValueInB = b.cells().get(aCell.getKey());
+            if (sameValueInB != null)
+                cells.put(aCell.getKey(), aCell.getValue() * sameValueInB);
+        }
+    }
+
+    /** Returns the result of taking this product */
+    public MapTensor result() {
+        return new MapTensor(dimensions, cells.build());
+    }
+
+}