Isolate ONNX implementations in separate DLL and NuGet (#462)

Abstraction of ONNX exporting to interfaces, and isolation of actual implementation to separate DLL. Creation of a new NuGet to isolate Protobuf dependency.

Microsoft.ML.sln

@@ -18,7 +18,7 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.ML.InferenceTesti
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.ML.Data", "src\Microsoft.ML.Data\Microsoft.ML.Data.csproj", "{AD92D96B-0E96-4F22-8DCE-892E13B1F282}"
 EndProject
-Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.ML.UniversalModelFormat", "src\Microsoft.ML.UniversalModelFormat\Microsoft.ML.UniversalModelFormat.csproj", "{65D0603E-B96C-4DFC-BDD1-705891B88C18}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.ML.Onnx", "src\Microsoft.ML.Onnx\Microsoft.ML.Onnx.csproj", "{65D0603E-B96C-4DFC-BDD1-705891B88C18}"
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.ML.StandardLearners", "src\Microsoft.ML.StandardLearners\Microsoft.ML.StandardLearners.csproj", "{707BB22C-7E5F-497A-8C2F-74578F675705}"
 EndProject

pkg/Microsoft.ML.Onnx/Microsoft.ML.Onnx.nupkgproj

@@ -0,0 +1,13 @@
+<Project Sdk="Microsoft.NET.Sdk" DefaultTargets="Pack">
+
+  <PropertyGroup>
+    <TargetFramework>netstandard2.0</TargetFramework>
+    <PackageDescription>ML.NET component for exporting ONNX Models</PackageDescription>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="../Microsoft.ML/Microsoft.ML.nupkgproj" />
+    <PackageReference Include="Google.Protobuf" Version="$(GoogleProtobufPackageVersion)" />
+  </ItemGroup>
+
+</Project>

pkg/Microsoft.ML.Onnx/Microsoft.ML.Onnx.symbols.nupkgproj

@@ -0,0 +1,5 @@
+<Project DefaultTargets="Pack">
+
+  <Import Project="Microsoft.ML.Onnx.nupkgproj" />
+
+</Project>

pkg/Microsoft.ML/Microsoft.ML.nupkgproj

@@ -6,7 +6,6 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Google.Protobuf" Version="$(GoogleProtobufPackageVersion)" />
     <PackageReference Include="Newtonsoft.Json" Version="$(NewtonsoftJsonPackageVersion)" />
     <PackageReference Include="System.Reflection.Emit.Lightweight" Version="$(SystemReflectionEmitLightweightPackageVersion)" />
     <PackageReference Include="System.Threading.Tasks.Dataflow" Version="$(SystemThreadingTasksDataflowPackageVersion)" />

src/Microsoft.ML.Console/Microsoft.ML.Console.csproj

@@ -19,13 +19,13 @@
     <ProjectReference Include="..\Microsoft.ML.KMeansClustering\Microsoft.ML.KMeansClustering.csproj" />
     <ProjectReference Include="..\Microsoft.ML.LightGBM\Microsoft.ML.LightGBM.csproj" />
     <ProjectReference Include="..\Microsoft.ML.Maml\Microsoft.ML.Maml.csproj" />
+    <ProjectReference Include="..\Microsoft.ML.Onnx\Microsoft.ML.Onnx.csproj" />
     <ProjectReference Include="..\Microsoft.ML.PCA\Microsoft.ML.PCA.csproj" />
     <ProjectReference Include="..\Microsoft.ML.PipelineInference\Microsoft.ML.PipelineInference.csproj" />
     <ProjectReference Include="..\Microsoft.ML.ResultProcessor\Microsoft.ML.ResultProcessor.csproj" />
     <ProjectReference Include="..\Microsoft.ML.StandardLearners\Microsoft.ML.StandardLearners.csproj" />
     <ProjectReference Include="..\Microsoft.ML.Sweeper\Microsoft.ML.Sweeper.csproj" />
     <ProjectReference Include="..\Microsoft.ML.Transforms\Microsoft.ML.Transforms.csproj" />
-    <ProjectReference Include="..\Microsoft.ML.UniversalModelFormat\Microsoft.ML.UniversalModelFormat.csproj" />
 
     <NativeAssemblyReference Include="FastTreeNative" />
     <NativeAssemblyReference Include="CpuMathNative" />

src/Microsoft.ML.Data/DataLoadSave/CompositeDataLoader.cs

@@ -85,7 +85,7 @@ private static VersionInfo GetVersionInfo()
         /// Returns the underlying data view of the composite loader.
         /// This can be used to programmatically explore the chain of transforms that's inside the composite loader.
         /// </summary>
-        internal IDataView View { get; }
+        public IDataView View { get; }
 
         /// <summary>
         /// Creates a loader according to the specified <paramref name="args"/>.

src/Microsoft.ML.Data/Microsoft.ML.Data.csproj

@@ -15,7 +15,6 @@
   <ItemGroup>
     <ProjectReference Include="..\Microsoft.ML.Core\Microsoft.ML.Core.csproj" />
     <ProjectReference Include="..\Microsoft.ML.CpuMath\Microsoft.ML.CpuMath.csproj" />
-    <ProjectReference Include="..\Microsoft.ML.UniversalModelFormat\Microsoft.ML.UniversalModelFormat.csproj" />
   </ItemGroup>
 
 </Project>

src/Microsoft.ML.Data/Model/Onnx/ICanSaveOnnx.cs

@@ -19,7 +19,7 @@ public interface ICanSaveOnnx
     }
 
     /// <summary>
-    /// This data model component is savable as Onnx.
+    /// This data model component is savable as ONNX.
     /// </summary>
     public interface ITransformCanSaveOnnx: ICanSaveOnnx, IDataTransform
     {

src/Microsoft.ML.Data/Model/Onnx/OnnxContext.cs

@@ -2,245 +2,101 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Collections.Generic;
-using System.Linq;
-using Microsoft.ML.Runtime.UniversalModelFormat.Onnx;
 using Microsoft.ML.Runtime.Data;
 
 namespace Microsoft.ML.Runtime.Model.Onnx
 {
     /// <summary>
-    /// A context for defining a ONNX output.
+    /// A context for defining a ONNX output. The context internally contains the model-in-progress being built. This
+    /// same context object is iteratively given to exportable components via the <see cref="ICanSaveOnnx"/> interface
+    /// and subinterfaces, that attempt to express their operations as ONNX nodes, if they can. At the point that it is
+    /// given to a component, all other components up to that component have already attempted to express themselves in
+    /// this context, with their outputs possibly available in the ONNX graph.
     /// </summary>
-    public sealed class OnnxContext
+    public abstract class OnnxContext
     {
-        private readonly List<NodeProto> _nodes;
-        private readonly List<OnnxUtils.ModelArgs> _inputs;
-        private readonly List<OnnxUtils.ModelArgs> _intermediateValues;
-        private readonly List<OnnxUtils.ModelArgs> _outputs;
-        private readonly Dictionary<string, string> _columnNameMap;
-        private readonly HashSet<string> _variableMap;
-        private readonly HashSet<string> _nodeNames;
-        private readonly string _name;
-        private readonly string _producerName;
-        private readonly IHost _host;
-        private readonly string _domain;
-        private readonly string _producerVersion;
-        private readonly long _modelVersion;
-
-        public OnnxContext(IHostEnvironment env, string name, string producerName,
-            string producerVersion, long modelVersion, string domain)
-        {
-            Contracts.CheckValue(env, nameof(env));
-            Contracts.CheckValue(name, nameof(name));
-            Contracts.CheckValue(name, nameof(domain));
-
-            _host = env.Register(nameof(OnnxContext));
-            _nodes = new List<NodeProto>();
-            _intermediateValues = new List<OnnxUtils.ModelArgs>();
-            _inputs = new List<OnnxUtils.ModelArgs>();
-            _outputs = new List<OnnxUtils.ModelArgs>();
-            _columnNameMap = new Dictionary<string, string>();
-            _variableMap = new HashSet<string>();
-            _nodeNames = new HashSet<string>();
-            _name = name;
-            _producerName = producerName;
-            _producerVersion = producerVersion;
-            _modelVersion = modelVersion;
-            _domain = domain;
-        }
-
-        public bool ContainsColumn(string colName) => _columnNameMap.ContainsKey(colName);
-
-        /// <summary>
-        /// Stops tracking a column. If removeVariable is true then it also removes the 
-        /// variable associated with it, this is useful in the event where an output variable is 
-        /// created before realizing the transform cannot actually save as ONNX.
-        /// </summary>
-        /// <param name="colName">IDataView column name to stop tracking</param>
-        /// <param name="removeVariable">Remove associated ONNX variable at the time.</param>
-        public void RemoveColumn(string colName, bool removeVariable)
-        {
-
-            if (removeVariable)
-            {
-                foreach (var val in _intermediateValues)
-                {
-                    if (val.Name == _columnNameMap[colName])
-                    {
-                        _intermediateValues.Remove(val);
-                        break;
-                    }
-                }
-            }
-
-            if (_columnNameMap.ContainsKey(colName))
-                _columnNameMap.Remove(colName);
-        }
-
-        /// <summary>
-        /// Removes an ONNX variable. If removeColumn is true then it also removes the 
-        /// IDataView column associated with it.
-        /// </summary>
-        /// <param name="variableName">ONNX variable to remove.</param>
-        /// <param name="removeColumn">IDataView column to stop tracking</param>
-        public void RemoveVariable(string variableName, bool removeColumn)
-        {
-            _host.Assert(_columnNameMap.ContainsValue(variableName));
-            if (removeColumn)
-            {
-                foreach (var val in _intermediateValues)
-                {
-                    if (val.Name == variableName)
-                    {
-                        _intermediateValues.Remove(val);
-                        break;
-                    }
-                }
-            }
-
-            string columnName = _columnNameMap.Single(kvp => string.Compare(kvp.Value, variableName) == 0).Key;
-
-            Contracts.Assert(_variableMap.Contains(columnName));
-
-            _columnNameMap.Remove(columnName);
-            _variableMap.Remove(columnName);
-        }
-
         /// <summary>
         /// Generates a unique name for the node based on a prefix.
         /// </summary>
-        public string GetNodeName(string prefix)
-        {
-            _host.CheckValue(prefix, nameof(prefix));
-            return GetUniqueName(prefix, c => _nodeNames.Contains(c));
-        }
+        /// <param name="prefix">The prefix for the node</param>
+        /// <returns>A name that has not yet been returned from this function, starting with <paramref name="prefix"/></returns>
+        public abstract string GetNodeName(string prefix);
 
         /// <summary>
-        /// Adds a node to the node list of the graph.
+        /// Looks up whether a given data view column has a mapping in the ONNX context. Once confirmed, callers can
+        /// safely call <see cref="GetVariableName(string)"/>.
         /// </summary>
-        /// <param name="node"></param>
-        public void AddNode(NodeProto node)
-        {
-            _host.CheckValue(node, nameof(node));
-            _host.Assert(!_nodeNames.Contains(node.Name));
-
-            _nodeNames.Add(node.Name);
-            _nodes.Add(node);
-        }
+        /// <param name="colName">The data view column name</param>
+        /// <returns>Whether the column is mapped in this context</returns>
+        public abstract bool ContainsColumn(string colName);
 
         /// <summary>
-        /// Generates a unique name based on a prefix.
+        /// Stops tracking a column.
         /// </summary>
-        private string GetUniqueName(string prefix, Func<string, bool> pred)
-        {
-            _host.CheckValue(prefix, nameof(prefix));
-            _host.CheckValue(pred, nameof(pred));
-
-            if (!pred(prefix))
-                return prefix;
-
-            int count = 0;
-            while (pred(prefix + count++)) ;
-            return prefix + --count;
-        }
+        /// <param name="colName">Column name to stop tracking</param>
+        /// <param name="removeVariable">Remove associated ONNX variable. This is useful in the event where an output
+        /// variable is created through <see cref="AddIntermediateVariable(ColumnType, string, bool)"/>before realizing
+        /// the transform cannot actually save as ONNX.</param>
+        public abstract void RemoveColumn(string colName, bool removeVariable = false);
 
         /// <summary>
-        /// Retrieves the variable name that maps to the IDataView column name at a 
-        /// given point in the pipeline execution.
+        /// Removes an ONNX variable. If removeColumn is true then it also removes the tracking for the <see
+        /// cref="IDataView"/> column associated with it.
         /// </summary>
-        /// <returns>Column Name mapping.</returns>
-        public string GetVariableName(string colName)
-        {
-            _host.CheckValue(colName, nameof(colName));
-            _host.Assert(_columnNameMap.ContainsKey(colName));
-
-            return _columnNameMap[colName];
-        }
-
-        /// <summary>
-        /// Retrieves the variable name that maps to the IDataView column name at a 
-        /// given point in the pipeline execution.
-        /// </summary>
-        /// <returns>Column Name mapping.</returns>
-        public string TryGetVariableName(string colName)
-        {
-            if (_columnNameMap.ContainsKey(colName))
-                return GetVariableName(colName);
-
-            return null;
-        }
-
-        /// <summary>
-        /// Generates a unique column name based on the IDataView column name if
-        /// there is a collision between names in the pipeline at any point.
-        /// </summary>
-        /// <param name="colName">IDataView column name.</param>
-        /// <returns>Unique variable name.</returns>
-        private string AddVariable(string colName)
-        {
-            _host.CheckValue(colName, nameof(colName));
-
-            if (!_columnNameMap.ContainsKey(colName))
-                _columnNameMap.Add(colName, colName);
-            else
-                _columnNameMap[colName] = GetUniqueName(colName, s => _variableMap.Contains(s));
-
-            _variableMap.Add(_columnNameMap[colName]);
-            return _columnNameMap[colName];
-        }
+        /// <param name="variableName">ONNX variable to remove. Note that this is an ONNX variable name, not an <see
+        /// cref="IDataView"/> column name</param>
+        /// <param name="removeColumn">IDataView column to stop tracking</param>
+        public abstract void RemoveVariable(string variableName, bool removeColumn);
 
         /// <summary>
-        /// Adds an intermediate column to the list.
+        /// ONNX variables are referred to by name. At each stage of a ML.NET pipeline, the corresponding
+        /// <see cref="IDataView"/>'s column names will map to a variable in the ONNX graph if the intermediate steps
+        /// used to calculate that value are things we knew how to save as ONNX. Retrieves the variable name that maps
+        /// to the <see cref="IDataView"/> column name at a given point in the pipeline execution. Callers should
+        /// probably confirm with <see cref="ContainsColumn(string)"/> whether a mapping for that data view column
+        /// already exists.
         /// </summary>
-        public string AddIntermediateVariable(ColumnType type, string colName, bool skip = false)
-        {
-
-            colName = AddVariable(colName);
-
-            //Let the runtime figure the shape.
-            if (!skip)
-            {
-                _host.CheckValue(type, nameof(type));
-
-                _intermediateValues.Add(OnnxUtils.GetModelArgs(type, colName));
-            }
-
-            return colName;
-        }
+        /// <param name="colName">The data view column name</param>
+        /// <returns>The ONNX variable name corresponding to that data view column</returns>
+        public abstract string GetVariableName(string colName);
 
         /// <summary>
-        /// Adds an output variable to the list.
+        /// Establishes a new mapping from an data view column in the context, if necessary generates a unique name, and
+        /// returns that newly allocated name.
         /// </summary>
-        public string AddOutputVariable(ColumnType type, string colName, List<long> dim = null)
-        {
-            _host.CheckValue(type, nameof(type));
-
-            if (!ContainsColumn(colName))
-                AddVariable(colName);
-
-            colName = GetVariableName(colName);
-            _outputs.Add(OnnxUtils.GetModelArgs(type, colName, dim));
-            return colName;
-        }
+        /// <param name="type">The data view type associated with this column name</param>
+        /// <param name="colName">The data view column name</param>
+        /// <param name="skip">Whether we should skip the process of establishing the mapping from data view column to
+        /// ONNX variable name.</param>
+        /// <returns>The returned value is the name of the variable corresponding </returns>
+        public abstract string AddIntermediateVariable(ColumnType type, string colName, bool skip = false);
 
         /// <summary>
-        /// Adds an input variable to the list.
+        /// Creates an ONNX node 
         /// </summary>
-        public void AddInputVariable(ColumnType type, string colName)
-        {
-            _host.CheckValue(type, nameof(type));
-            _host.CheckValue(colName, nameof(colName));
-
-            colName = AddVariable(colName);
-            _inputs.Add(OnnxUtils.GetModelArgs(type, colName));
-        }
+        /// <param name="opType">The name of the ONNX operator to apply</param>
+        /// <param name="inputs">The names of the variables as inputs</param>
+        /// <param name="outputs">The names of the variables to create as outputs,
+        /// which ought to have been something returned from <see cref="AddIntermediateVariable(ColumnType, string, bool)"/></param>
+        /// <param name="name">The name of the operator, which ought to be something returned from <see cref="GetNodeName(string)"/></param>
+        /// <param name="domain">The domain of the ONNX operator, if non-default</param>
+        /// <returns>A node added to the in-progress ONNX graph, that attributes can be set on</returns>
+        public abstract OnnxNode CreateNode(string opType, IEnumerable<string> inputs,
+            IEnumerable<string> outputs, string name, string domain = null);
 
         /// <summary>
-        /// Makes the ONNX model based on the context.
+        /// Convenience alternative to <see cref="CreateNode(string, IEnumerable{string}, IEnumerable{string}, string, string)"/>
+        /// for the case where there is exactly one input and output.
         /// </summary>
-        public ModelProto MakeModel()
-            => OnnxUtils.MakeModel(_nodes, _producerName, _name, _domain, _producerVersion, _modelVersion, _inputs, _outputs, _intermediateValues);
+        /// <param name="opType">The name of the ONNX operator to apply</param>
+        /// <param name="input">The name of the variable as input</param>
+        /// <param name="output">The name of the variable as output,
+        /// which ought to have been something returned from <see cref="OnnxContext.AddIntermediateVariable(ColumnType, string, bool)"/></param>
+        /// <param name="name">The name of the operator, which ought to be something returned from <see cref="OnnxContext.GetNodeName(string)"/></param>
+        /// <param name="domain">The domain of the ONNX operator, if non-default</param>
+        /// <returns>A node added to the in-progress ONNX graph, that attributes can be set on</returns>
+        public OnnxNode CreateNode(string opType, string input, string output, string name, string domain = null)
+            => CreateNode(opType, new[] { input }, new[] { output }, name, domain);
     }
 }