Allow compatible changes to stored tensors

Allow increasing the size of tensor dimensions without making stored
data incompatible.

2 files changed, 42 insertions, 1 deletions

diff --git a/vespajlib/src/main/java/com/yahoo/tensor/TensorType.java b/vespajlib/src/main/java/com/yahoo/tensor/TensorType.java
index 7eae9539e77..8ff9774fc7d 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/TensorType.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/TensorType.java
@@ -82,6 +82,21 @@ public class TensorType {
      * i.e if the given type is a generalization of this type.
      */
     public boolean isAssignableTo(TensorType generalization) {
+        return isConvertibleOrAssignableTo(generalization, false);
+    }
+
+    /**
+     * Returns whether this type can be converted to the given type.
+     * This is true if this type isAssignableTo the given type or
+     * if it is not assignable only because it has a shorter dimension length
+     * than the given type in some shared dimension(s), as it can then be
+     * converted to the given type by zero padding.
+     */
+    public boolean isConvertibleTo(TensorType generalization) {
+        return isConvertibleOrAssignableTo(generalization, true);
+    }
+
+    private boolean isConvertibleOrAssignableTo(TensorType generalization, boolean convertible) {
         if (generalization.dimensions().size() != this.dimensions().size()) return false;
         for (int i = 0; i < generalization.dimensions().size(); i++) {
             Dimension thisDimension = this.dimensions().get(i);
@@ -90,7 +105,12 @@ public class TensorType {
             if ( ! thisDimension.name().equals(generalizationDimension.name())) return false;
             if (generalizationDimension.size().isPresent()) {
                 if ( ! thisDimension.size().isPresent()) return false;
-                if ( ! thisDimension.size().get().equals(generalizationDimension.size().get()) ) return false;
+                if (convertible) {
+                    if (thisDimension.size().get() > generalizationDimension.size().get()) return false;
+                }
+                else { // assignable
+                    if (!thisDimension.size().get().equals(generalizationDimension.size().get())) return false;
+                }
             }
         }
         return true;
diff --git a/vespajlib/src/test/java/com/yahoo/tensor/TensorTypeTestCase.java b/vespajlib/src/test/java/com/yahoo/tensor/TensorTypeTestCase.java
index c3e31fad2da..eef0b090fd1 100644
--- a/vespajlib/src/test/java/com/yahoo/tensor/TensorTypeTestCase.java
+++ b/vespajlib/src/test/java/com/yahoo/tensor/TensorTypeTestCase.java
@@ -12,6 +12,7 @@ import static org.junit.Assert.fail;
 
 /**
  * @author geirst
+ * @author bratseth
  */
 public class TensorTypeTestCase {
 
@@ -75,6 +76,18 @@ public class TensorTypeTestCase {
         assertIsAssignableTo("tensor(x{},y[10])", "tensor(x{},y[])");
     }
 
+    @Test
+    public void testConvertibleTo() {
+        assertIsConvertibleTo("tensor(x[])", "tensor(x[])");
+        assertUnconvertibleTo("tensor(x[])", "tensor(y[])");
+        assertIsConvertibleTo("tensor(x[10])", "tensor(x[])");
+        assertUnconvertibleTo("tensor(x[])", "tensor(x[10])");
+        assertUnconvertibleTo("tensor(x[10])", "tensor(x[5])");
+        assertIsConvertibleTo("tensor(x[5])", "tensor(x[10])"); // Different from assignable
+        assertUnconvertibleTo("tensor(x{})", "tensor(x[])");
+        assertIsConvertibleTo("tensor(x{},y[10])", "tensor(x{},y[])");
+    }
+
     private static void assertTensorType(String typeSpec) {
         assertTensorType(typeSpec, typeSpec);
     }
@@ -100,4 +113,12 @@ public class TensorTypeTestCase {
         assertFalse(TensorType.fromSpec(specificType).isAssignableTo(TensorType.fromSpec(generalType)));
     }
 
+    private void assertIsConvertibleTo(String specificType, String generalType) {
+        assertTrue(TensorType.fromSpec(specificType).isConvertibleTo(TensorType.fromSpec(generalType)));
+    }
+
+    private void assertUnconvertibleTo(String specificType, String generalType) {
+        assertFalse(TensorType.fromSpec(specificType).isConvertibleTo(TensorType.fromSpec(generalType)));
+    }
+
 }