Don't expose initial aggregator values when reducing empty tensors

2 files changed, 12 insertions, 2 deletions

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 86f23487efb..879daefaf72 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/Reduce.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/Reduce.java
@@ -114,7 +114,9 @@ public class Reduce<NAMETYPE extends Name> extends PrimitiveTensorFunction<NAMET
 
         // Special case: Reduce all
         if (dimensions.isEmpty() || dimensions.size() == argument.type().dimensions().size())
-            if (argument.type().dimensions().size() == 1 && argument instanceof IndexedTensor)
+            if (argument.isEmpty())
+                return Tensor.from(0.0);
+            else if (argument.type().dimensions().size() == 1 && argument instanceof IndexedTensor)
                 return reduceIndexedVector((IndexedTensor)argument, aggregator);
             else
                 return reduceAllGeneral(argument, aggregator);
diff --git a/vespajlib/src/test/java/com/yahoo/tensor/functions/ReduceTestCase.java b/vespajlib/src/test/java/com/yahoo/tensor/functions/ReduceTestCase.java
index 21fed1745b9..7d052467f64 100644
--- a/vespajlib/src/test/java/com/yahoo/tensor/functions/ReduceTestCase.java
+++ b/vespajlib/src/test/java/com/yahoo/tensor/functions/ReduceTestCase.java
@@ -16,7 +16,6 @@ public class ReduceTestCase {
 
     @Test
     public void testReduce() {
-        assertNan(Tensor.from("tensor(x{})", "{}").median());
         assertEquals(1.0, Tensor.from("tensor(x[1])", "[1]").median().asDouble(), delta);
         assertEquals(1.5, Tensor.from("tensor(x[2])", "[1, 2]").median().asDouble(), delta);
         assertEquals(3.0, Tensor.from("tensor(x[7])", "[3, 1, 1, 1, 4, 4, 4]").median().asDouble(), delta);
@@ -28,6 +27,15 @@ public class ReduceTestCase {
         assertNan(Tensor.Builder.of("tensor(x[1])").cell(Double.NaN, 0).build().median());
     }
 
+    @Test
+    public void testEmptyReduce() {
+        assertEquals(0.0, Tensor.from("tensor(x[3],y{})", "{}").avg().asDouble(), delta);
+        assertEquals(0.0, Tensor.from("tensor(x[3],y{})", "{}").max().asDouble(), delta);
+        assertEquals(0.0, Tensor.from("tensor(x[3],y{})", "{}").median().asDouble(), delta);
+        assertEquals(0.0, Tensor.from("tensor(x[3],y{})", "{}").min().asDouble(), delta);
+        assertEquals(0.0, Tensor.from("tensor(x[3],y{})", "{}").prod().asDouble(), delta);
+    }
+
     private void assertNan(Tensor tensor) {
         assertTrue(tensor + " is NaN", Double.isNaN(tensor.asDouble()));
     }