From 865dac49dcf420cd00b9be0f08ee219e4f519aee Mon Sep 17 00:00:00 2001
From: Henning Baldersheim <balder@yahoo-inc.com>
Date: Wed, 17 Jan 2024 22:55:30 +0100
Subject: Create set of indexes to remove once.

---
 vespajlib/src/main/java/com/yahoo/tensor/Tensor.java        |  6 +++++-
 .../src/main/java/com/yahoo/tensor/functions/Reduce.java    | 13 +++++++++----
 2 files changed, 14 insertions(+), 5 deletions(-)

(limited to 'vespajlib/src')

diff --git a/vespajlib/src/main/java/com/yahoo/tensor/Tensor.java b/vespajlib/src/main/java/com/yahoo/tensor/Tensor.java
index d0d01d29b26..8a4179cdc1a 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/Tensor.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/Tensor.java
@@ -62,7 +62,11 @@ public interface Tensor {
     /** Returns whether this have any cells */
     default boolean isEmpty() { return size() == 0; }
 
-    /** Returns the number of cells in this */
+    /**
+     *  Returns the number of cells in this.
+     *  TODO Figure how to best return an int instead of a long
+     *  An int is large enough, and java is far better at int base loops than long
+     **/
     long size();
 
     /** Returns the value of a cell, or 0.0 if this cell does not exist */
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/Reduce.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/Reduce.java
index 5327457a438..76ca98124b8 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/Reduce.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/Reduce.java
@@ -128,10 +128,13 @@ public class Reduce<NAMETYPE extends Name> extends PrimitiveTensorFunction<NAMET
         TensorType reducedType = outputType(argument.type(), dimensions);
 
         // Reduce cells
-        Map<TensorAddress, ValueAggregator> aggregatingCells = new HashMap<>();
+        Set<Integer> indexesToRemove = createIndexesOfDimensionsToRemove(argument.type(), dimensions);
+        // TODO cells.size() is most likely an overestimate, and might need a better heuristic
+        // But the upside is larger than teh downside.
+        Map<TensorAddress, ValueAggregator> aggregatingCells = new HashMap<>((int)argument.size());
         for (Iterator<Tensor.Cell> i = argument.cellIterator(); i.hasNext(); ) {
             Map.Entry<TensorAddress, Double> cell = i.next();
-            TensorAddress reducedAddress = reduceDimensions(cell.getKey(), argument.type(), reducedType, dimensions);
+            TensorAddress reducedAddress = reduceDimensions(indexesToRemove, cell.getKey(), reducedType);
             aggregatingCells.putIfAbsent(reducedAddress, ValueAggregator.ofType(aggregator));
             aggregatingCells.get(reducedAddress).aggregate(cell.getValue());
         }
@@ -142,12 +145,14 @@ public class Reduce<NAMETYPE extends Name> extends PrimitiveTensorFunction<NAMET
         return reducedBuilder.build();
 
     }
-
-    private static TensorAddress reduceDimensions(TensorAddress address, TensorType argumentType, TensorType reducedType, List<String> dimensions) {
+    private static Set<Integer> createIndexesOfDimensionsToRemove(TensorType argumentType, List<String> dimensions) {
         Set<Integer> indexesToRemove = new HashSet<>(dimensions.size()*2);
         for (String dimensionToRemove : dimensions)
             indexesToRemove.add(argumentType.indexOfDimension(dimensionToRemove).get());
+        return indexesToRemove;
+    }
 
+    private static TensorAddress reduceDimensions(Set<Integer> indexesToRemove, TensorAddress address, TensorType reducedType) {
         String[] reducedLabels = new String[reducedType.dimensions().size()];
         int reducedLabelIndex = 0;
         for (int i = 0; i < address.size(); i++)
-- 
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