Use MappedTensor to represent tensor with no dimensions or values

5 files changed, 24 insertions, 27 deletions

diff --git a/vespajlib/src/main/java/com/yahoo/tensor/IndexedTensor.java b/vespajlib/src/main/java/com/yahoo/tensor/IndexedTensor.java
index 4654f53647f..deee4aa02b6 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/IndexedTensor.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/IndexedTensor.java
@@ -103,7 +103,6 @@ public class IndexedTensor implements Tensor {
      * @throws IndexOutOfBoundsException if any of the indexes are out of bound or a wrong number of indexes are given
      */
     public double get(int ... indexes) {
-        if (values.length == 0) return Double.NaN;
         return values[toValueIndex(indexes, dimensionSizes)];
     }
 
@@ -157,7 +156,7 @@ public class IndexedTensor implements Tensor {
     @Override
     public Map<TensorAddress, Double> cells() {
         if (dimensionSizes.dimensions() == 0)
-            return values.length == 0 ? Collections.emptyMap() : Collections.singletonMap(TensorAddress.empty, values[0]);
+            return Collections.singletonMap(TensorAddress.empty, values[0]);
         
         ImmutableMap.Builder<TensorAddress, Double> builder = new ImmutableMap.Builder<>();
         Indexes indexes = Indexes.of(dimensionSizes, dimensionSizes, values.length);
@@ -221,7 +220,7 @@ public class IndexedTensor implements Tensor {
         public TensorType type() { return type; }
 
         @Override
-        public abstract IndexedTensor build();
+        public abstract Tensor build();
 
     }
     
@@ -269,11 +268,14 @@ public class IndexedTensor implements Tensor {
         }
 
         @Override
-        public IndexedTensor build() {
+        public Tensor build() {
             // Note that we do not check for no NaN's here for performance reasons. 
             // NaN's don't get lost so leaving them in place should be quite benign 
-            if (values.length == 1 && Double.isNaN(values[0]))
-                values = new double[0];
+
+            // An empty tensor with no dimensions is mapped
+            if (values.length == 1 && Double.isNaN(values[0]) && type.dimensions().isEmpty())
+                return MappedTensor.Builder.of(type).build();
+
             IndexedTensor tensor = new IndexedTensor(type, sizes, values);
             // prevent further modification
             sizes = null;
@@ -316,24 +318,28 @@ public class IndexedTensor implements Tensor {
         }
 
         @Override
-        public IndexedTensor build() {
-            if (firstDimension == null) // empty
-                return new IndexedTensor(type, new DimensionSizes.Builder(type.dimensions().size()).build(), new double[] {});
+        public Tensor build() {
+            if (firstDimension == null && type.dimensions().isEmpty()) // empty
+                return MappedTensor.Builder.of(type).build();
             if (type.dimensions().isEmpty()) // single number
                 return new IndexedTensor(type, new DimensionSizes.Builder(type.dimensions().size()).build(), new double[] {(Double) firstDimension.get(0) });
 
             DimensionSizes dimensionSizes = findDimensionSizes(firstDimension);
             double[] values = new double[dimensionSizes.totalSize()];
-            fillValues(0, 0, firstDimension, dimensionSizes, values);
+            if (firstDimension != null)
+                fillValues(0, 0, firstDimension, dimensionSizes, values);
             return new IndexedTensor(type, dimensionSizes, values);
         }
         
         private DimensionSizes findDimensionSizes(List<Object> firstDimension) {
             List<Integer> dimensionSizeList = new ArrayList<>(type.dimensions().size());
-            findDimensionSizes(0, dimensionSizeList, firstDimension);
+            if (firstDimension != null)
+                findDimensionSizes(0, dimensionSizeList, firstDimension);
             DimensionSizes.Builder b = new DimensionSizes.Builder(type.dimensions().size()); // may be longer than the list but that's correct
-            for (int i = 0; i < b.dimensions(); i++)
-                b.set(i, dimensionSizeList.get(i));
+            for (int i = 0; i < b.dimensions(); i++) {
+                if (i < dimensionSizeList.size())
+                    b.set(i, dimensionSizeList.get(i));
+            }
             return b.build();
         }
 
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/Tensor.java b/vespajlib/src/main/java/com/yahoo/tensor/Tensor.java
index 51d40a89f3b..29c508ce12f 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/Tensor.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/Tensor.java
@@ -213,10 +213,9 @@ public interface Tensor {
 
     static String contentToString(Tensor tensor) {
         List<java.util.Map.Entry<TensorAddress, Double>> cellEntries = new ArrayList<>(tensor.cells().entrySet());
-        if (tensor.type().dimensions().isEmpty()) { // TODO: Decide on one way to represent degeneration to number
+        if (tensor.type().dimensions().isEmpty()) {
             if (cellEntries.isEmpty()) return "{}";
-            double value = cellEntries.get(0).getValue();
-            return value == 0.0 ? "{}" : "{" + value +"}";
+            return "{" + cellEntries.get(0).getValue() +"}";
         }
         
         Collections.sort(cellEntries, java.util.Map.Entry.<TensorAddress, Double>comparingByKey());
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/TensorType.java b/vespajlib/src/main/java/com/yahoo/tensor/TensorType.java
index 82f36972a47..fbc469c1829 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/TensorType.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/TensorType.java
@@ -53,9 +53,6 @@ public class TensorType {
         return TensorTypeParser.fromSpec(specString);
     }
 
-    /** Returns true if all dimensions of this are indexed */
-    public boolean isIndexed() { return dimensions().stream().allMatch(d -> d.isIndexed()); }
-    
     /** Returns an immutable list of the dimensions of this */
     public List<Dimension> dimensions() { return dimensions; }
     
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/Join.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/Join.java
index ceade39ce42..f295e129a0f 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/Join.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/Join.java
@@ -113,7 +113,7 @@ public class Join extends PrimitiveTensorFunction {
     
     /** Join a tensor into a superspace */
     private Tensor subspaceJoin(Tensor subspace, Tensor superspace, TensorType joinedType, boolean reversedArgumentOrder) {
-        if (subspace.type().isIndexed() && superspace.type().isIndexed())
+        if (subspace instanceof IndexedTensor && superspace instanceof IndexedTensor)
             return indexedSubspaceJoin((IndexedTensor) subspace, (IndexedTensor) superspace, joinedType, reversedArgumentOrder);
         else
             return generalSubspaceJoin(subspace, superspace, joinedType, reversedArgumentOrder);
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/serialization/DenseBinaryFormat.java b/vespajlib/src/main/java/com/yahoo/tensor/serialization/DenseBinaryFormat.java
index c3284131be0..0a97576d5b7 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/serialization/DenseBinaryFormat.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/serialization/DenseBinaryFormat.java
@@ -41,13 +41,8 @@ public class DenseBinaryFormat implements BinaryFormat {
 
     private void encodeCells(GrowableByteBuffer buffer, Tensor tensor) {
         Iterator<Double> i = tensor.valueIterator();
-        if ( ! i.hasNext()) { // no values: Encode as NaN, as 0 dimensions may also mean 1 value
-            buffer.putDouble(Double.NaN);
-        }
-        else {
-            while (i.hasNext())
-                buffer.putDouble(i.next());
-        }
+        while (i.hasNext())
+            buffer.putDouble(i.next());
     }
 
     @Override