Vespa global model import

16 files changed, 235 insertions, 48 deletions

diff --git a/config-model/src/test/integration/vespa/models/constant1asLarge.json b/config-model/src/test/integration/vespa/models/constant1asLarge.json
new file mode 100644
index 00000000000..d2944d255af
--- /dev/null
+++ b/config-model/src/test/integration/vespa/models/constant1asLarge.json
@@ -0,0 +1,7 @@
+{
+  "cells": [
+    { "address": { "x": "0" }, "value": 0.5 },
+    { "address": { "x": "1" }, "value": 1.5 },
+    { "address": { "x": "2" }, "value": 2.5 }
+  ]
+}
\ No newline at end of file
diff --git a/config-model/src/test/integration/vespa/models/example.model b/config-model/src/test/integration/vespa/models/example.model
new file mode 100644
index 00000000000..9579be4e44c
--- /dev/null
+++ b/config-model/src/test/integration/vespa/models/example.model
@@ -0,0 +1,25 @@
+model example {
+
+    # All inputs that are not scalar (aka 0-dimensional tensor) must be declared
+    input1: tensor(name{}, x[3])
+    input2: tensor(x[3])
+
+    constants {
+        constant1: tensor(x[3]):{{x:0}:0.5, {x:1}:1.5, {x:2}:2.5}
+        constant2: 3.0
+    }
+
+    constant constant1asLarge {
+        type: tensor(x[3])
+        file: constant1asLarge.json
+    }
+
+    function foo1() {
+        expression: max(sum(input1 * input2, name) * constant1, x) * constant2
+    }
+
+    function foo2() {
+        expression: max(sum(input1 * input2, name) * constant1asLarge, x) * constant2
+    }
+
+}
\ No newline at end of file
diff --git a/config-model/src/test/integration/vespa/services.xml b/config-model/src/test/integration/vespa/services.xml
new file mode 100644
index 00000000000..aa1c0223bdf
--- /dev/null
+++ b/config-model/src/test/integration/vespa/services.xml
@@ -0,0 +1,6 @@
+<!-- Copyright 2018 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root. -->
+<services>
+    <container version="1.0">
+
+    </container>
+</services>
diff --git a/config-model/src/test/java/com/yahoo/searchdefinition/processing/VespaMlModelTestCase.java b/config-model/src/test/java/com/yahoo/searchdefinition/processing/VespaMlModelTestCase.java
new file mode 100644
index 00000000000..a75699d2a1d
--- /dev/null
+++ b/config-model/src/test/java/com/yahoo/searchdefinition/processing/VespaMlModelTestCase.java
@@ -0,0 +1,77 @@
+// Copyright 2019 Oath Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.searchdefinition.processing;
+
+import com.yahoo.config.application.api.ApplicationPackage;
+import com.yahoo.io.IOUtils;
+import com.yahoo.path.Path;
+import com.yahoo.searchdefinition.derived.RawRankProfile;
+import com.yahoo.vespa.model.VespaModel;
+import com.yahoo.vespa.model.ml.ImportedModelTester;
+import org.junit.After;
+import org.junit.Test;
+
+import java.io.IOException;
+import java.util.Optional;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * Tests adding Vespa ranking expression based models in the models/ dir
+ *
+ * @author bratseth
+ */
+public class VespaMlModelTestCase {
+
+    private final Path applicationDir = Path.fromString("src/test/integration/vespa/");
+
+    private final String expectedRankConfig =
+            "constant(constant1).type : tensor(x[3])\n" +
+            "constant(constant1).value : tensor(x[3]):{{x:0}:0.5,{x:1}:1.5,{x:2}:2.5}\n" +
+            "rankingExpression(foo1).rankingScript : reduce(reduce(input1 * input2, sum, name) * constant(constant1), max, x) * 3.0\n" +
+            "rankingExpression(foo1).input2.type : tensor(x[3])\n" +
+            "rankingExpression(foo1).input1.type : tensor(name{},x[3])\n" +
+            "rankingExpression(foo2).rankingScript : max(reduce(input1 * input2, sum, name) * constant1asLarge,x) * 3.0\n" +
+            "rankingExpression(foo2).input2.type : tensor(x[3])\n" +
+            "rankingExpression(foo2).input1.type : tensor(name{},x[3])\n";
+
+    /** The model name */
+    private final String name = "example";
+
+    @After
+    public void removeGeneratedModelFiles() {
+        IOUtils.recursiveDeleteDir(applicationDir.append(ApplicationPackage.MODELS_GENERATED_DIR).toFile());
+    }
+
+    @Test
+    public void testGlobalVespaModel() throws IOException {
+        ImportedModelTester tester = new ImportedModelTester(name, applicationDir);
+        VespaModel model = tester.createVespaModel();
+        tester.assertLargeConstant("constant1asLarge", model, Optional.of(3L));
+        assertEquals(expectedRankConfig, rankConfigOf("example", model));
+
+        // At this point the expression is stored - copy application to another location which do not have a models dir
+        Path storedAppDir = applicationDir.append("copy");
+        try {
+            storedAppDir.toFile().mkdirs();
+            IOUtils.copy(applicationDir.append("services.xml").toString(), storedAppDir.append("services.xml").toString());
+            IOUtils.copyDirectory(applicationDir.append(ApplicationPackage.MODELS_GENERATED_DIR).toFile(),
+                                  storedAppDir.append(ApplicationPackage.MODELS_GENERATED_DIR).toFile());
+            ImportedModelTester storedTester = new ImportedModelTester(name, storedAppDir);
+            VespaModel storedModel = storedTester.createVespaModel();
+            storedTester.assertLargeConstant("constant1asLarge", model, Optional.of(3L));
+            assertEquals(expectedRankConfig, rankConfigOf("example", storedModel));
+        }
+        finally {
+            IOUtils.recursiveDeleteDir(storedAppDir.toFile());
+        }
+    }
+
+    private String rankConfigOf(String rankProfileName, VespaModel model) {
+        StringBuilder b = new StringBuilder();
+        RawRankProfile profile = model.rankProfileList().getRankProfile(rankProfileName);
+        for (var property : profile.configProperties())
+            b.append(property.getFirst()).append(" : ").append(property.getSecond()).append("\n");
+        return b.toString();
+    }
+
+}
diff --git a/config-model/src/test/java/com/yahoo/vespa/model/ml/ImportedModelTester.java b/config-model/src/test/java/com/yahoo/vespa/model/ml/ImportedModelTester.java
index 563572b4af6..41811738ea4 100644
--- a/config-model/src/test/java/com/yahoo/vespa/model/ml/ImportedModelTester.java
+++ b/config-model/src/test/java/com/yahoo/vespa/model/ml/ImportedModelTester.java
@@ -1,6 +1,7 @@
 // Copyright 2018 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.vespa.model.ml;
 
+import ai.vespa.rankingexpression.importer.vespa.VespaImporter;
 import com.google.common.collect.ImmutableList;
 import com.yahoo.config.model.ApplicationPackageTester;
 import ai.vespa.rankingexpression.importer.configmodelview.MlModelImporter;
@@ -8,10 +9,12 @@ import com.yahoo.config.model.deploy.DeployState;
 import com.yahoo.io.GrowableByteBuffer;
 import com.yahoo.io.IOUtils;
 import com.yahoo.path.Path;
+import com.yahoo.searchdefinition.RankProfile;
 import com.yahoo.searchdefinition.RankingConstant;
 import ai.vespa.rankingexpression.importer.onnx.OnnxImporter;
 import ai.vespa.rankingexpression.importer.tensorflow.TensorFlowImporter;
 import ai.vespa.rankingexpression.importer.xgboost.XGBoostImporter;
+import com.yahoo.searchdefinition.derived.RawRankProfile;
 import com.yahoo.tensor.Tensor;
 import com.yahoo.tensor.serialization.TypedBinaryFormat;
 import com.yahoo.vespa.model.VespaModel;
@@ -34,7 +37,8 @@ public class ImportedModelTester {
 
     private final ImmutableList<MlModelImporter> importers = ImmutableList.of(new TensorFlowImporter(),
                                                                               new OnnxImporter(),
-                                                                              new XGBoostImporter());
+                                                                              new XGBoostImporter(),
+                                                                              new VespaImporter());
 
     private final String modelName;
     private final Path applicationDir;
diff --git a/document/src/main/java/com/yahoo/document/json/readers/TensorReader.java b/document/src/main/java/com/yahoo/document/json/readers/TensorReader.java
index 9a1a37caade..a3d2a157073 100644
--- a/document/src/main/java/com/yahoo/document/json/readers/TensorReader.java
+++ b/document/src/main/java/com/yahoo/document/json/readers/TensorReader.java
@@ -10,7 +10,7 @@ import static com.yahoo.document.json.readers.JsonParserHelpers.*;
 
 /**
  * Reads the tensor format described at
- * http://docs.vespa.ai/documentation/reference/document-json-put-format.html#tensor
+ * http://docs.vespa.ai/documentation/reference/document-json-format.html#tensor
  */
 public class TensorReader {
 
@@ -20,6 +20,7 @@ public class TensorReader {
     public static final String TENSOR_VALUE = "value";
 
     public static void fillTensor(TokenBuffer buffer, TensorFieldValue tensorFieldValue) {
+        // TODO: Switch implementation to om.yahoo.tensor.serialization.JsonFormat.decode
         Tensor.Builder tensorBuilder = Tensor.Builder.of(tensorFieldValue.getDataType().getTensorType());
         expectObjectStart(buffer.currentToken());
         int initNesting = buffer.nesting();
diff --git a/model-integration/src/main/java/ai/vespa/rankingexpression/importer/ImportedModel.java b/model-integration/src/main/java/ai/vespa/rankingexpression/importer/ImportedModel.java
index 36cb8c4f1cf..90529ccdca0 100644
--- a/model-integration/src/main/java/ai/vespa/rankingexpression/importer/ImportedModel.java
+++ b/model-integration/src/main/java/ai/vespa/rankingexpression/importer/ImportedModel.java
@@ -204,7 +204,7 @@ public class ImportedModel implements ImportedMlModel {
             ImmutableMap.Builder<String, TensorType> inputs = new ImmutableMap.Builder<>();
             // Note: We're naming inputs by their actual name (used in the expression, given by what the input maps *to*
             // in the model, as these are the names which must actually be bound, if we are to avoid creating an
-            // "input mapping" to accommodate this complexity in
+            // "input mapping" to accommodate this complexity
             for (Map.Entry<String, String> inputEntry : inputs().entrySet())
                 inputs.put(inputEntry.getValue(), owner().inputs().get(inputEntry.getValue()));
             return inputs.build();
diff --git a/model-integration/src/main/java/ai/vespa/rankingexpression/importer/xgboost/XGBoostImporter.java b/model-integration/src/main/java/ai/vespa/rankingexpression/importer/xgboost/XGBoostImporter.java
index ac462cc39eb..686cf6cd2df 100644
--- a/model-integration/src/main/java/ai/vespa/rankingexpression/importer/xgboost/XGBoostImporter.java
+++ b/model-integration/src/main/java/ai/vespa/rankingexpression/importer/xgboost/XGBoostImporter.java
@@ -1,11 +1,13 @@
 // Copyright 2018 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package ai.vespa.rankingexpression.importer.xgboost;
 
+import com.yahoo.io.IOUtils;
 import com.yahoo.searchlib.rankingexpression.RankingExpression;
 import ai.vespa.rankingexpression.importer.ImportedModel;
 import ai.vespa.rankingexpression.importer.ModelImporter;
 import com.yahoo.searchlib.rankingexpression.parser.ParseException;
 
+import java.io.BufferedReader;
 import java.io.File;
 import java.io.IOException;
 
@@ -22,7 +24,27 @@ public class XGBoostImporter extends ModelImporter {
         File modelFile = new File(modelPath);
         if ( ! modelFile.isFile()) return false;
 
-        return modelFile.toString().endsWith(".json"); // No other models ends by json yet
+        return modelFile.toString().endsWith(".json") && probe(modelFile);
+    }
+
+    /**
+     * Returns true if the give file looks like an XGBoost json file.
+     * Currently, we just check if the file has an array on the top level.
+     */
+    private boolean probe(File modelFile) {
+        try {
+            BufferedReader reader = IOUtils.createReader(modelFile.getAbsolutePath());
+            String line;
+            while ((line = reader.readLine()) != null) {
+                line = line.trim();
+                if (line.startsWith("[")) return true;
+                if ( ! line.isEmpty()) return false;
+            }
+            return false;
+        }
+        catch (IOException e) {
+            throw new IllegalArgumentException("Could not read '" + modelFile + "'", e);
+        }
     }
 
     @Override
diff --git a/model-integration/src/main/javacc/ModelParser.jj b/model-integration/src/main/javacc/ModelParser.jj
index 18dfb4c68ed..a5510dd89f3 100644
--- a/model-integration/src/main/javacc/ModelParser.jj
+++ b/model-integration/src/main/javacc/ModelParser.jj
@@ -23,13 +23,16 @@ PARSER_BEGIN(ModelParser)
 
 package ai.vespa.rankingexpression.importer.vespa.parser;
 
+import java.io.File;
 import java.io.Reader;
 import java.io.StringReader;
 import java.util.List;
 import java.util.ArrayList;
 import ai.vespa.rankingexpression.importer.ImportedModel;
+import com.yahoo.io.IOUtils;
 import com.yahoo.tensor.TensorType;
 import com.yahoo.tensor.Tensor;
+import com.yahoo.tensor.serialization.JsonFormat;
 import com.yahoo.searchlib.rankingexpression.RankingExpression;
 
 /**
@@ -99,6 +102,7 @@ TOKEN :
 | < #BRACE_ML_LEVEL_3: <BRACE_ML_CONTENT> "}" >
 | < #BRACE_ML_CONTENT: (~["{","}"])* >
 | < #SEARCHLIB_SKIP: ([" ","\f","\n","\r","\t"])+ >
+| < CONSTANT: "constant" >
 | < CONSTANTS: "constants" >
 | < FILE: "file" >
 | < URI: "uri" >
@@ -147,7 +151,7 @@ void modelContent() :
 {
 }
 {
-    ( <NL> | input() | constants() | function() )*
+    ( <NL> | input() | constants() | largeConstant() | function() )*
 }
 
 /** Declared input variables (aka features). All non-scalar inputs must be declared. */
@@ -233,15 +237,6 @@ String tensorValue() :
     }
 }
 
-TensorType tensorTypeWithPrefix(String errorMessage) :
-{
-    TensorType type;
-}
-{
-    <TYPE> <COLON> type=tensorType(errorMessage)
-    { return type; }
-}
-
 TensorType tensorType(String errorMessage) :
 {
     String tensorTypeString;
@@ -259,47 +254,38 @@ TensorType tensorType(String errorMessage) :
     }
 }
 
-//----------------------------------------
-/** Consumes a constant block of model. */
-/*
+/** Consumes a large constant. */
 void largeConstant() :
 {
     String name;
-    RankingConstant constant;
+    Tensor value;
 }
 {
-    ( <CONSTANT> name = identifier()
-        {
-//            constant = new RankingConstant(name);
-        }
-      lbrace() (rankingConstantItem(constant) (<NL>)*)+ <RBRACE> )
-    {
-    }
+    ( <CONSTANT> name = identifier() lbrace() value = largeConstantBody(name) <RBRACE> )
+    { model.largeConstant(name, value); }
 }
-*/
 
-/** Consumes a constant block. */
-/*
-void rankingConstantItem(RankingConstant constant) :
+// TODO: Add support in ImportedModel for passing a large tensor through as a file/Uri pointer instead of reading it here
+Tensor largeConstantBody(String name) :
 {
     String path = null;
     TensorType type = null;
 }
 {
-    ( (<FILE> <COLON> path = filePath() { } (<NL>)*) { constant.setFileName(path); }
-      | (<URI> <COLON> path = uriPath() { } (<NL>)*) { constant.setUri(path); }
-      | type = tensorTypeWithPrefix(rankingConstantErrorMessage(constant.getName())) (<NL>)* { constant.setType(type); }
-    )
+    (   <FILE> <COLON> path = filePath()
+//      | (<URI> <COLON> path = uriPath() TODO
+      | <TYPE> <COLON> type = tensorType("Constant '" + name + "'")
+      | <NL>
+    )+
     {
-        return null;
+        try {
+            return JsonFormat.decode(type, IOUtils.readFileBytes(new File(new File(model.source()).getParent(), path)));
+        }
+        catch (Exception e) {
+            throw new IllegalArgumentException("Could not read constant '" + name + "'", e);
+        }
     }
 }
-*/
-
-String rankingConstantErrorMessage(String name) : {}
-{
-    { return "For ranking constant ' " + name + "'"; }
-}
 
 String filePath() : { }
 {
@@ -312,7 +298,6 @@ String uriPath() : { }
     ( <URI_PATH> )
     { return token.image; }
 }
-//----------------------------------------
 
 /** Consumes an expression token and returns its image. */
 String expression() :
diff --git a/model-integration/src/test/java/ai/vespa/rankingexpression/importer/vespa/VespaImportTestCase.java b/model-integration/src/test/java/ai/vespa/rankingexpression/importer/vespa/VespaImportTestCase.java
index 1be2b7a4183..4c8890f6476 100644
--- a/model-integration/src/test/java/ai/vespa/rankingexpression/importer/vespa/VespaImportTestCase.java
+++ b/model-integration/src/test/java/ai/vespa/rankingexpression/importer/vespa/VespaImportTestCase.java
@@ -2,8 +2,11 @@
 package ai.vespa.rankingexpression.importer.vespa;
 
 import ai.vespa.rankingexpression.importer.ImportedModel;
+import ai.vespa.rankingexpression.importer.configmodelview.ImportedMlFunction;
 import org.junit.Test;
 
+import java.util.List;
+
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
@@ -25,8 +28,24 @@ public class VespaImportTestCase {
         assertEquals("tensor(x[3]):{{x:0}:0.5,{x:1}:1.5,{x:2}:2.5}", model.smallConstants().get("constant1"));
         assertEquals("tensor():{3.0}", model.smallConstants().get("constant2"));
 
-        assertEquals("max(reduce(input1 * input2, sum, name),x) * constant2",
-                     model.expressions().get("foo").getRoot().toString());
+        assertEquals(1, model.largeConstants().size());
+        assertEquals("tensor(x[3]):{{x:0}:0.5,{x:1}:1.5,{x:2}:2.5}", model.largeConstants().get("constant1asLarge"));
+
+        assertEquals(2, model.expressions().size());
+        assertEquals("max(reduce(input1 * input2, sum, name) * constant1,x) * constant2",
+                     model.expressions().get("foo1").getRoot().toString());
+        assertEquals("max(reduce(input1 * input2, sum, name) * constant1asLarge,x) * constant2",
+                     model.expressions().get("foo2").getRoot().toString());
+
+        List<ImportedMlFunction> functions = model.outputExpressions();
+        assertEquals(2, functions.size());
+        ImportedMlFunction foo1Function = functions.get(0);
+        assertEquals(2, foo1Function.arguments().size());
+        assertTrue(foo1Function.arguments().contains("input1"));
+        assertTrue(foo1Function.arguments().contains("input2"));
+        assertEquals(2, foo1Function.argumentTypes().size());
+        assertEquals("tensor(name{},x[3])", foo1Function.argumentTypes().get("input1"));
+        assertEquals("tensor(x[3])", foo1Function.argumentTypes().get("input2"));
     }
 
     @Test
diff --git a/model-integration/src/test/java/ai/vespa/rankingexpression/importer/xgboost/XGBoostImportTestCase.java b/model-integration/src/test/java/ai/vespa/rankingexpression/importer/xgboost/XGBoostImportTestCase.java
index 67a3b17255c..6d54b63db4b 100644
--- a/model-integration/src/test/java/ai/vespa/rankingexpression/importer/xgboost/XGBoostImportTestCase.java
+++ b/model-integration/src/test/java/ai/vespa/rankingexpression/importer/xgboost/XGBoostImportTestCase.java
@@ -22,6 +22,7 @@ public class XGBoostImportTestCase {
         assertNotNull(expression);
         assertEquals("if (f29 < -0.1234567, if (f56 < -0.242398, 1.71218, -1.70044), if (f109 < 0.8723473, -1.94071, 1.85965)) + if (f60 < -0.482947, if (f29 < -4.2387498, 0.784718, -0.96853), -6.23624)",
                      expression.getRoot().toString());
+        assertEquals(1, model.outputExpressions().size());
     }
 
 }
diff --git a/model-integration/src/test/models/vespa/constant1asLarge.json b/model-integration/src/test/models/vespa/constant1asLarge.json
new file mode 100644
index 00000000000..d2944d255af
--- /dev/null
+++ b/model-integration/src/test/models/vespa/constant1asLarge.json
@@ -0,0 +1,7 @@
+{
+  "cells": [
+    { "address": { "x": "0" }, "value": 0.5 },
+    { "address": { "x": "1" }, "value": 1.5 },
+    { "address": { "x": "2" }, "value": 2.5 }
+  ]
+}
\ No newline at end of file
diff --git a/model-integration/src/test/models/vespa/example.model b/model-integration/src/test/models/vespa/example.model
index c0ea461db09..9579be4e44c 100644
--- a/model-integration/src/test/models/vespa/example.model
+++ b/model-integration/src/test/models/vespa/example.model
@@ -9,8 +9,17 @@ model example {
         constant2: 3.0
     }
 
-    function foo() {
-        expression: max(sum(input1 * input2, name), x) * constant2
+    constant constant1asLarge {
+        type: tensor(x[3])
+        file: constant1asLarge.json
+    }
+
+    function foo1() {
+        expression: max(sum(input1 * input2, name) * constant1, x) * constant2
+    }
+
+    function foo2() {
+        expression: max(sum(input1 * input2, name) * constant1asLarge, x) * constant2
     }
 
 }
\ No newline at end of file
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/transform/Simplifier.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/transform/Simplifier.java
index e8e2fdf2454..1181dafad3f 100644
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/transform/Simplifier.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/transform/Simplifier.java
@@ -11,6 +11,8 @@ import com.yahoo.searchlib.rankingexpression.rule.EmbracedNode;
 import com.yahoo.searchlib.rankingexpression.rule.ExpressionNode;
 import com.yahoo.searchlib.rankingexpression.rule.IfNode;
 import com.yahoo.searchlib.rankingexpression.rule.ReferenceNode;
+import com.yahoo.searchlib.rankingexpression.rule.TensorFunctionNode;
+import com.yahoo.tensor.functions.TensorFunction;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -120,6 +122,7 @@ public class Simplifier extends ExpressionTransformer<TransformContext> {
     private boolean isConstant(ExpressionNode node) {
         if (node instanceof ConstantNode) return true;
         if (node instanceof ReferenceNode) return false;
+        if (node instanceof TensorFunctionNode) return false; // TODO: We could support asking it if it is constant
         if ( ! (node instanceof CompositeNode)) return false;
         for (ExpressionNode child : ((CompositeNode)node).children()) {
             if ( ! isConstant(child)) return false;
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/serialization/JsonFormat.java b/vespajlib/src/main/java/com/yahoo/tensor/serialization/JsonFormat.java
index 3213982355b..6382361f187 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/serialization/JsonFormat.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/serialization/JsonFormat.java
@@ -1,7 +1,11 @@
 // Copyright 2018 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.tensor.serialization;
 
+import com.yahoo.slime.ArrayTraverser;
 import com.yahoo.slime.Cursor;
+import com.yahoo.slime.Inspector;
+import com.yahoo.slime.JsonDecoder;
+import com.yahoo.slime.ObjectTraverser;
 import com.yahoo.slime.Slime;
 import com.yahoo.tensor.Tensor;
 import com.yahoo.tensor.TensorAddress;
@@ -17,9 +21,7 @@ import java.util.Iterator;
 // TODO: We should probably move reading of this format from the document module to here
 public class JsonFormat {
 
-    /**
-     * Serialize the given tensor into JSON format
-     */
+    /** Serializes the given tensor into JSON format */
     public static byte[] encode(Tensor tensor) {
         Slime slime = new Slime();
         Cursor root = slime.setObject();
@@ -38,4 +40,19 @@ public class JsonFormat {
             addressObject.setString(type.dimensions().get(i).name(), address.label(i));
     }
 
+    /** Deserializes the given tensor from JSON format */
+    // TODO: Add explicit validation (valid() checks) below
+    public static Tensor decode(TensorType type, byte[] jsonTensorValue) {
+        Tensor.Builder tensorBuilder = Tensor.Builder.of(type);
+        Inspector root = new JsonDecoder().decode(new Slime(), jsonTensorValue).get();
+        Inspector cells = root.field("cells");
+        cells.traverse((ArrayTraverser) (__, cell) -> decodeCell(cell, tensorBuilder.cell()));
+        return tensorBuilder.build();
+    }
+
+    private static void decodeCell(Inspector cell, Tensor.Builder.CellBuilder cellBuilder) {
+        cell.field("address").traverse((ObjectTraverser) (dimension, label) -> cellBuilder.label(dimension, label.asString()));
+        cellBuilder.value(cell.field("value").asDouble());
+    }
+
 }
diff --git a/vespajlib/src/test/java/com/yahoo/tensor/serialization/JsonFormatTestCase.java b/vespajlib/src/test/java/com/yahoo/tensor/serialization/JsonFormatTestCase.java
index 16af413f2f0..5a025b6eb96 100644
--- a/vespajlib/src/test/java/com/yahoo/tensor/serialization/JsonFormatTestCase.java
+++ b/vespajlib/src/test/java/com/yahoo/tensor/serialization/JsonFormatTestCase.java
@@ -26,6 +26,8 @@ public class JsonFormatTestCase {
                      "{\"address\":{\"x\":\"c\",\"y\":\"d\"},\"value\":3.0}" +
                      "]}",
                      new String(json, StandardCharsets.UTF_8));
+        Tensor decoded = JsonFormat.decode(tensor.type(), json);
+        assertEquals(tensor, decoded);
     }
 
     @Test
@@ -44,6 +46,8 @@ public class JsonFormatTestCase {
                      "{\"address\":{\"x\":\"1\",\"y\":\"1\"},\"value\":7.0}" +
                      "]}",
                      new String(json, StandardCharsets.UTF_8));
+        Tensor decoded = JsonFormat.decode(tensor.type(), json);
+        assertEquals(tensor, decoded);
     }
 
 }