Merge pull request #26501 from vespa-engine/arnej/add-transformer-support

Arnej/add transformer support

17 files changed, 264 insertions, 29 deletions

diff --git a/config-model/src/main/java/com/yahoo/schema/expressiontransforms/ConstantTensorTransformer.java b/config-model/src/main/java/com/yahoo/schema/expressiontransforms/ConstantTensorTransformer.java
index 4e320594918..a9eea3d2ead 100644
--- a/config-model/src/main/java/com/yahoo/schema/expressiontransforms/ConstantTensorTransformer.java
+++ b/config-model/src/main/java/com/yahoo/schema/expressiontransforms/ConstantTensorTransformer.java
@@ -2,14 +2,18 @@
 package com.yahoo.schema.expressiontransforms;
 
 import com.yahoo.schema.FeatureNames;
+import com.yahoo.searchlib.rankingexpression.RankingExpression;
 import com.yahoo.searchlib.rankingexpression.Reference;
 import com.yahoo.searchlib.rankingexpression.evaluation.TensorValue;
 import com.yahoo.searchlib.rankingexpression.evaluation.Value;
+import com.yahoo.searchlib.rankingexpression.parser.ParseException;
 import com.yahoo.searchlib.rankingexpression.rule.CompositeNode;
 import com.yahoo.searchlib.rankingexpression.rule.ExpressionNode;
 import com.yahoo.searchlib.rankingexpression.rule.ReferenceNode;
+import com.yahoo.searchlib.rankingexpression.rule.TensorFunctionNode;
 import com.yahoo.searchlib.rankingexpression.transform.ExpressionTransformer;
 
+import java.io.StringReader;
 import java.util.ArrayList;
 import java.util.List;
 
@@ -22,6 +26,9 @@ public class ConstantTensorTransformer extends ExpressionTransformer<RankProfile
 
     @Override
     public ExpressionNode transform(ExpressionNode node, RankProfileTransformContext context) {
+        if (node instanceof TensorFunctionNode tfn) {
+            node = tfn.withTransformedExpressions(expr -> transform(expr, context));
+        }
         if (node instanceof ReferenceNode) {
             return transformFeature((ReferenceNode) node, context);
         } else if (node instanceof CompositeNode) {
@@ -32,6 +39,32 @@ public class ConstantTensorTransformer extends ExpressionTransformer<RankProfile
     }
 
     private ExpressionNode transformFeature(ReferenceNode node, RankProfileTransformContext context) {
+        Reference ref = node.reference();
+        String name = ref.name();
+        var args = ref.arguments();
+        if (name.equals("onnx") && args.size() == 1) {
+            var arg = args.expressions().get(0);
+            var models = context.rankProfile().onnxModels();
+            var model = models.get(arg.toString());
+            if (model != null) {
+                for (var entry : model.getInputMap().entrySet()) {
+                    String source = entry.getValue();
+                    var reader = new StringReader(source);
+                    try {
+                        var asExpression = new RankingExpression(reader);
+                        String transformed = transform(asExpression.getRoot(), context).toString();
+                        if (! source.equals(transformed)) {
+                            // not sure about this:
+                            throw new IllegalStateException("unexpected rewrite: " + source + " => " + transformed + " for onnx input " + entry.getKey());
+                            // consider instead: model.addInputNameMapping(entry.getKey(), transformed, true);
+                        }
+                    } catch (ParseException e) {
+                        throw new IllegalArgumentException("illegal onnx input '" + source + "': " + e.getMessage());
+                    }
+                }
+                return node;
+            }
+        }
         if ( ! node.getArguments().isEmpty() && ! FeatureNames.isSimpleFeature(node.reference())) {
             return transformArguments(node, context);
         } else {
diff --git a/config-model/src/main/java/com/yahoo/schema/expressiontransforms/InputRecorder.java b/config-model/src/main/java/com/yahoo/schema/expressiontransforms/InputRecorder.java
index 84d0997b12e..af072c5b59a 100644
--- a/config-model/src/main/java/com/yahoo/schema/expressiontransforms/InputRecorder.java
+++ b/config-model/src/main/java/com/yahoo/schema/expressiontransforms/InputRecorder.java
@@ -55,20 +55,7 @@ public class InputRecorder extends ExpressionTransformer<InputRecorderContext> {
                 }
                 return transformChildren(t, childContext);
             }
-            if (f instanceof DynamicTensor d) {
-                for (var tf : d.cellGeneratorFunctions()) {
-                    if (tf instanceof TensorFunctionNode.ExpressionTensorFunction expr) {
-                        transform(expr.wrappedExpression(), context);
-                    }
-                }
-            }
-            if (f instanceof Slice s) {
-                for (var tf : s.selectorFunctions()) {
-                    if (tf instanceof TensorFunctionNode.ExpressionTensorFunction expr) {
-                        transform(expr.wrappedExpression(), context);
-                    }
-                }
-            }
+            node = t.withTransformedExpressions(expr -> transform(expr, context));
         }
         if (node instanceof CompositeNode c)
             return transformChildren(c, context);
diff --git a/config-model/src/test/derived/scalar_constant/rank-profiles.cfg b/config-model/src/test/derived/scalar_constant/rank-profiles.cfg
new file mode 100644
index 00000000000..5b494fa46fb
--- /dev/null
+++ b/config-model/src/test/derived/scalar_constant/rank-profiles.cfg
@@ -0,0 +1,18 @@
+rankprofile[].name "default"
+rankprofile[].fef.property[].name "rankingExpression(makevector).rankingScript"
+rankprofile[].fef.property[].value "tensor(x[3]):{{x:0}:0.25,{x:1}:0.5,{x:2}:0.75}"
+rankprofile[].fef.property[].name "rankingExpression(makevector).type"
+rankprofile[].fef.property[].value "tensor(x[3])"
+rankprofile[].fef.property[].name "vespa.rank.firstphase"
+rankprofile[].fef.property[].value "rankingExpression(firstphase)"
+rankprofile[].fef.property[].name "rankingExpression(firstphase).rankingScript"
+rankprofile[].fef.property[].value "reduce(rankingExpression(makevector), sum)"
+rankprofile[].name "unranked"
+rankprofile[].fef.property[].name "vespa.rank.firstphase"
+rankprofile[].fef.property[].value "value(0)"
+rankprofile[].fef.property[].name "vespa.hitcollector.heapsize"
+rankprofile[].fef.property[].value "0"
+rankprofile[].fef.property[].name "vespa.hitcollector.arraysize"
+rankprofile[].fef.property[].value "0"
+rankprofile[].fef.property[].name "vespa.dump.ignoredefaultfeatures"
+rankprofile[].fef.property[].value "true"
diff --git a/config-model/src/test/derived/scalar_constant/test.sd b/config-model/src/test/derived/scalar_constant/test.sd
new file mode 100644
index 00000000000..5c05e0ba941
--- /dev/null
+++ b/config-model/src/test/derived/scalar_constant/test.sd
@@ -0,0 +1,20 @@
+# Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+schema test {
+    document test {
+        field title type string {
+            indexing: index | summary
+        }
+    }
+    rank-profile default {
+        constants {
+            constant(foobar) double: 0.5
+        }
+        function makevector() {
+            expression: tensor(x[3]):[0.25, constant(foobar), 0.75]
+        }
+        first-phase {
+            expression: sum(makevector())
+        }
+    }
+}
diff --git a/config-model/src/test/derived/vector_constant/ax_plus_b.onnx b/config-model/src/test/derived/vector_constant/ax_plus_b.onnx
new file mode 100644
index 00000000000..17282d13dc3
--- /dev/null
+++ b/config-model/src/test/derived/vector_constant/ax_plus_b.onnx
@@ -0,0 +1,23 @@
+:©

+ 
+matrix_X
+vector_AXA"MatMul
+
+XA
+vector_Bvector_Y"AddlrZ
+matrix_X
+
+
+Z
+vector_A
+
+
+Z
+vector_B
+
+
+b
+vector_Y
+
+
+B
\ No newline at end of file
diff --git a/config-model/src/test/derived/vector_constant/rank-profiles.cfg b/config-model/src/test/derived/vector_constant/rank-profiles.cfg
new file mode 100644
index 00000000000..87edec6ca24
--- /dev/null
+++ b/config-model/src/test/derived/vector_constant/rank-profiles.cfg
@@ -0,0 +1,26 @@
+rankprofile[].name "default"
+rankprofile[].fef.property[].name "constant(bb).value"
+rankprofile[].fef.property[].value "tensor(d0[2]):[4.0, 5.0]"
+rankprofile[].fef.property[].name "constant(bb).type"
+rankprofile[].fef.property[].value "tensor(d0[2])"
+rankprofile[].fef.property[].name "constant(aa).value"
+rankprofile[].fef.property[].value "tensor(d1[3]):[1.0, 2.0, 3.0]"
+rankprofile[].fef.property[].name "constant(aa).type"
+rankprofile[].fef.property[].value "tensor(d1[3])"
+rankprofile[].fef.property[].name "rankingExpression(indirect_a).rankingScript"
+rankprofile[].fef.property[].value "tensor(d1[3]):{{d1:0}:2.0,{d1:1}:(constant(aa){d1:0}),{d1:2}:(constant(bb){d0:(2.0)})}"
+rankprofile[].fef.property[].name "rankingExpression(indirect_a).type"
+rankprofile[].fef.property[].value "tensor(d1[3])"
+rankprofile[].fef.property[].name "vespa.rank.firstphase"
+rankprofile[].fef.property[].value "rankingExpression(firstphase)"
+rankprofile[].fef.property[].name "rankingExpression(firstphase).rankingScript"
+rankprofile[].fef.property[].value "reduce(onnx(inside).foobar, sum)"
+rankprofile[].name "unranked"
+rankprofile[].fef.property[].name "vespa.rank.firstphase"
+rankprofile[].fef.property[].value "value(0)"
+rankprofile[].fef.property[].name "vespa.hitcollector.heapsize"
+rankprofile[].fef.property[].value "0"
+rankprofile[].fef.property[].name "vespa.hitcollector.arraysize"
+rankprofile[].fef.property[].value "0"
+rankprofile[].fef.property[].name "vespa.dump.ignoredefaultfeatures"
+rankprofile[].fef.property[].value "true"
diff --git a/config-model/src/test/derived/vector_constant/ranking-constants.cfg b/config-model/src/test/derived/vector_constant/ranking-constants.cfg
new file mode 100644
index 00000000000..8637be8f175
--- /dev/null
+++ b/config-model/src/test/derived/vector_constant/ranking-constants.cfg
@@ -0,0 +1,3 @@
+constant[].name "xx"
+constant[].fileref "const_xx.json"
+constant[].type "tensor(d0[2],d1[3])"
diff --git a/config-model/src/test/derived/vector_constant/test.sd b/config-model/src/test/derived/vector_constant/test.sd
new file mode 100644
index 00000000000..508bd6505a7
--- /dev/null
+++ b/config-model/src/test/derived/vector_constant/test.sd
@@ -0,0 +1,33 @@
+schema test {
+    document test {
+        field extra type string {
+        }
+    }
+    constant xx {
+        file: const_xx.json
+        type: tensor(d0[2],d1[3])
+    }
+    rank-profile default {
+        constants {
+            constant(aa) tensor(d1[3]): [1,2,3]
+            bb           tensor(d0[2]): [4,5]
+	   dd           double:        2
+        }
+        function indirect_a() {
+            expression: tensor(d1[3]): [constant(dd), constant(aa){d1:0}, constant(bb){d0:(constant(dd))}]
+        }
+        onnx-model inside {
+            file: ax_plus_b.onnx
+            input vector_A: indirect_a
+            input matrix_X: constant(xx)
+            input vector_B: constant(bb)
+            output vector_Y: foobar
+        }
+        first-phase {
+            expression: sum(onnx(inside).foobar)
+        }
+        # function unused() {
+        #    expression: constant(aa)*constant(bb)
+        # }
+    }
+}
diff --git a/config-model/src/test/java/com/yahoo/schema/derived/SmallConstantsTestCase.java b/config-model/src/test/java/com/yahoo/schema/derived/SmallConstantsTestCase.java
new file mode 100644
index 00000000000..09352eb59fa
--- /dev/null
+++ b/config-model/src/test/java/com/yahoo/schema/derived/SmallConstantsTestCase.java
@@ -0,0 +1,27 @@
+// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.schema.derived;
+
+import com.yahoo.schema.parser.ParseException;
+import org.junit.jupiter.api.Test;
+import java.io.IOException;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+/**
+ * Tests constants in rank-profile
+ *
+ * @author arnej
+ */
+public class SmallConstantsTestCase extends AbstractExportingTestCase {
+
+    @Test
+    void testScalarInRankProfile() throws IOException, ParseException {
+        assertCorrectDeriving("scalar_constant");
+    }
+
+    @Test
+    void testVectorInRankProfile() throws IOException, ParseException {
+        assertCorrectDeriving("vector_constant");
+    }
+
+}
diff --git a/model-evaluation/src/main/java/ai/vespa/models/evaluation/BindingExtractor.java b/model-evaluation/src/main/java/ai/vespa/models/evaluation/BindingExtractor.java
index bc71e51655c..8cdd5387acd 100644
--- a/model-evaluation/src/main/java/ai/vespa/models/evaluation/BindingExtractor.java
+++ b/model-evaluation/src/main/java/ai/vespa/models/evaluation/BindingExtractor.java
@@ -96,6 +96,11 @@ class BindingExtractor {
             for (ExpressionNode child : tfn.children()) {
                 result.merge(extractBindTargets(child));
             }
+            // ignore return value:
+            tfn.withTransformedExpressions(expr -> {
+                    result.merge(extractBindTargets(expr));
+                    return expr;
+                });
             var f = tfn.function();
             if (f instanceof Generate) {
                 var tt = f.type(null);
@@ -103,20 +108,6 @@ class BindingExtractor {
                     result.removeTarget(dim.name());
                 }
             }
-            else if (f instanceof Slice<?> s) {
-                for (var selectorFunc : s.selectorFunctions()) {
-                    if (selectorFunc instanceof TensorFunctionNode.ExpressionTensorFunction expr) {
-                        result.merge(extractBindTargets(expr.wrappedExpression()));
-                    }
-                }
-            }
-            else if (f instanceof DynamicTensor<?> d) {
-                for (var tf : d.cellGeneratorFunctions()) {
-                    if (tf instanceof TensorFunctionNode.ExpressionTensorFunction expr) {
-                        result.merge(extractBindTargets(expr.wrappedExpression()));
-                    }
-                }
-            }
             return result;
         }
         else if (isOnnx(node)) {
diff --git a/searchlib/abi-spec.json b/searchlib/abi-spec.json
index de3ec9648d1..f3fe86e261f 100644
--- a/searchlib/abi-spec.json
+++ b/searchlib/abi-spec.json
@@ -1696,6 +1696,7 @@
       "public void <init>(com.yahoo.tensor.functions.TensorFunction)",
       "public com.yahoo.tensor.functions.TensorFunction function()",
       "public java.util.List children()",
+      "public com.yahoo.searchlib.rankingexpression.rule.ExpressionNode withTransformedExpressions(java.util.function.Function)",
       "public com.yahoo.searchlib.rankingexpression.rule.CompositeNode setChildren(java.util.List)",
       "public java.lang.StringBuilder toString(java.lang.StringBuilder, com.yahoo.searchlib.rankingexpression.rule.SerializationContext, java.util.Deque, com.yahoo.searchlib.rankingexpression.rule.CompositeNode)",
       "public com.yahoo.tensor.TensorType type(com.yahoo.tensor.evaluation.TypeContext)",
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/TensorFunctionNode.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/TensorFunctionNode.java
index 7577c65527b..41ece967491 100644
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/TensorFunctionNode.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/TensorFunctionNode.java
@@ -25,6 +25,7 @@ import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
+import java.util.function.Function;
 import java.util.stream.Collectors;
 
 /**
@@ -58,6 +59,25 @@ public class TensorFunctionNode extends CompositeNode {
             return new TensorFunctionNode(f);
     }
 
+    private static ScalarFunction<Reference> transform(ScalarFunction<Reference> input,
+                                                       Function<ExpressionNode, ExpressionNode> transformer)
+    {
+        if (input instanceof ExpressionScalarFunction wrapper) {
+            ExpressionNode transformed = transformer.apply(wrapper.expression);
+            return new ExpressionScalarFunction(transformed);
+        }
+        return input;
+    }
+
+    public ExpressionNode withTransformedExpressions(Function<ExpressionNode, ExpressionNode> transformer) {
+        if (function instanceof ExpressionTensorFunction etf) {
+            ExpressionNode orig = etf.expression;
+            return transformer.apply(orig);
+        }
+        TensorFunction<Reference> transformed = function.withTransformedFunctions(fun -> transform(fun, transformer));
+        return new TensorFunctionNode(transformed);
+    }
+
     @Override
     public CompositeNode setChildren(List<ExpressionNode> children) {
         List<TensorFunction<Reference>> wrappedChildren = children.stream()
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/transform/ConstantDereferencer.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/transform/ConstantDereferencer.java
index 39afcfff541..225b260f403 100644
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/transform/ConstantDereferencer.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/transform/ConstantDereferencer.java
@@ -7,6 +7,7 @@ import com.yahoo.searchlib.rankingexpression.rule.CompositeNode;
 import com.yahoo.searchlib.rankingexpression.rule.ConstantNode;
 import com.yahoo.searchlib.rankingexpression.rule.ExpressionNode;
 import com.yahoo.searchlib.rankingexpression.rule.ReferenceNode;
+import com.yahoo.searchlib.rankingexpression.rule.TensorFunctionNode;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -20,6 +21,9 @@ public class ConstantDereferencer extends ExpressionTransformer<TransformContext
 
     @Override
     public ExpressionNode transform(ExpressionNode node, TransformContext context) {
+        if (node instanceof TensorFunctionNode tfn) {
+            node = tfn.withTransformedExpressions(expr -> transform(expr, context));
+        }
         if (node instanceof ReferenceNode)
             return transformFeature((ReferenceNode) node, context);
         else if (node instanceof CompositeNode)
diff --git a/vespajlib/abi-spec.json b/vespajlib/abi-spec.json
index e45b13a6eb0..88872fef8a1 100644
--- a/vespajlib/abi-spec.json
+++ b/vespajlib/abi-spec.json
@@ -2765,6 +2765,7 @@
       "public void <init>(com.yahoo.tensor.functions.TensorFunction, java.util.List)",
       "public java.util.List arguments()",
       "public java.util.List selectorFunctions()",
+      "public com.yahoo.tensor.functions.TensorFunction withTransformedFunctions(java.util.function.Function)",
       "public com.yahoo.tensor.functions.Slice withArguments(java.util.List)",
       "public com.yahoo.tensor.functions.PrimitiveTensorFunction toPrimitive()",
       "public com.yahoo.tensor.Tensor evaluate(com.yahoo.tensor.evaluation.EvaluationContext)",
@@ -2810,7 +2811,8 @@
       "public abstract java.lang.String toString(com.yahoo.tensor.functions.ToStringContext)",
       "public java.util.Optional asScalarFunction()",
       "public java.lang.String toString()",
-      "public abstract int hashCode()"
+      "public abstract int hashCode()",
+      "public com.yahoo.tensor.functions.TensorFunction withTransformedFunctions(java.util.function.Function)"
     ],
     "fields" : [ ]
   },
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/DynamicTensor.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/DynamicTensor.java
index 61d3acf6338..630eeb81d13 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/DynamicTensor.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/DynamicTensor.java
@@ -12,8 +12,10 @@ import com.yahoo.tensor.evaluation.TypeContext;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.LinkedHashMap;
 import java.util.Map;
 import java.util.Objects;
+import java.util.function.Function;
 
 /**
  * A function which is a tensor whose values are computed by individual lambda functions on evaluation.
@@ -82,6 +84,17 @@ public abstract class DynamicTensor<NAMETYPE extends Name> extends PrimitiveTens
             return result;
         }
 
+        public TensorFunction<NAMETYPE> withTransformedFunctions(
+                Function<ScalarFunction<NAMETYPE>, ScalarFunction<NAMETYPE>> transformer)
+        {
+            Map<TensorAddress, ScalarFunction<NAMETYPE>> transformedCells = new LinkedHashMap<>();
+            for (var orig : cells.entrySet()) {
+                var transformed = transformer.apply(orig.getValue());
+                transformedCells.put(orig.getKey(), transformed);
+            }
+            return new MappedDynamicTensor<>(type(), transformedCells);
+        }
+
         @Override
         public Tensor evaluate(EvaluationContext<NAMETYPE> context) {
             Tensor.Builder builder = Tensor.Builder.of(type());
@@ -134,6 +147,17 @@ public abstract class DynamicTensor<NAMETYPE extends Name> extends PrimitiveTens
             return result;
         }
 
+        public TensorFunction<NAMETYPE> withTransformedFunctions(
+                Function<ScalarFunction<NAMETYPE>, ScalarFunction<NAMETYPE>> transformer)
+        {
+            List<ScalarFunction<NAMETYPE>> transformedCells = new ArrayList<>();
+            for (var orig : cells) {
+                var transformed = transformer.apply(orig);
+                transformedCells.add(transformed);
+            }
+            return new IndexedDynamicTensor<>(type(), transformedCells);
+        }
+
         @Override
         public Tensor evaluate(EvaluationContext<NAMETYPE> context) {
             IndexedTensor.BoundBuilder builder = (IndexedTensor.BoundBuilder)Tensor.Builder.of(type());
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/Slice.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/Slice.java
index 87e24306031..066d75bcd9c 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/Slice.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/Slice.java
@@ -16,6 +16,7 @@ import java.util.Iterator;
 import java.util.List;
 import java.util.Objects;
 import java.util.Optional;
+import java.util.function.Function;
 import java.util.function.Predicate;
 import java.util.stream.Collectors;
 
@@ -56,6 +57,22 @@ public class Slice<NAMETYPE extends Name> extends PrimitiveTensorFunction<NAMETY
         return result;
     }
 
+    public TensorFunction<NAMETYPE> withTransformedFunctions(
+            Function<ScalarFunction<NAMETYPE>, ScalarFunction<NAMETYPE>> transformer)
+    {
+        List<DimensionValue<NAMETYPE>> transformedAddress = new ArrayList<>();
+        for (var orig : subspaceAddress) {
+            var idxFun = orig.index();
+            if (idxFun.isPresent()) {
+                var transformed = transformer.apply(idxFun.get());
+                transformedAddress.add(new DimensionValue<NAMETYPE>(orig.dimension(), transformed));
+            } else {
+                transformedAddress.add(orig);
+            }
+        }
+        return new Slice<>(argument, transformedAddress);
+    }
+
     @Override
     public Slice<NAMETYPE> withArguments(List<TensorFunction<NAMETYPE>> arguments) {
         if (arguments.size() != 1)
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/functions/TensorFunction.java b/vespajlib/src/main/java/com/yahoo/tensor/functions/TensorFunction.java
index 503f414d8eb..bf5eaeb6c2e 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/functions/TensorFunction.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/functions/TensorFunction.java
@@ -10,6 +10,7 @@ import com.yahoo.tensor.evaluation.TypeContext;
 
 import java.util.List;
 import java.util.Optional;
+import java.util.function.Function;
 
 /**
  * A representation of a tensor function which is able to be translated to a set of primitive
@@ -72,4 +73,9 @@ public abstract class TensorFunction<NAMETYPE extends Name> {
     @Override
     public abstract int hashCode();
 
+    public TensorFunction<NAMETYPE> withTransformedFunctions(
+            Function<ScalarFunction<NAMETYPE>, ScalarFunction<NAMETYPE>> transformer)
+    {
+        return this;
+    }
 }