Remove duplicate value-to-key mapping transform for multiclass string…

… labels (dotnet#283)

src/Microsoft.ML.Auto/PipelineSuggesters/PipelineSuggester.cs

@@ -35,8 +35,7 @@ public static SuggestedPipeline GetNextInferredPipeline(MLContext context,
         {
             var availableTrainers = RecipeInference.AllowedTrainers(context, task, 
                 ColumnInformationUtil.BuildColumnInfo(columns), trainerWhitelist);
-            var transforms = CalculateTransforms(context, columns, task);
-            //var transforms = TransformInferenceApi.InferTransforms(context, columns, task);
+            var transforms = TransformInferenceApi.InferTransforms(context, task, columns);
 
             // if we haven't run all pipelines once
             if (history.Count() < availableTrainers.Count())
@@ -213,21 +212,5 @@ private static bool SampleHyperparameters(MLContext context, SuggestedTrainer tr
 
             return true;
         }
-
-        private static IEnumerable<SuggestedTransform> CalculateTransforms(
-            MLContext context,
-            (string, DataViewType, ColumnPurpose, ColumnDimensions)[] columns,
-            TaskKind task)
-        {
-            var transforms = TransformInferenceApi.InferTransforms(context, columns).ToList();
-            // this is a work-around for ML.NET bug tracked by https://github.com/dotnet/machinelearning/issues/1969
-            if (task == TaskKind.MulticlassClassification)
-            {
-                var labelColumn = columns.First(c => c.Item3 == ColumnPurpose.Label).Item1;
-                var transform = ValueToKeyMappingExtension.CreateSuggestedTransform(context, labelColumn, labelColumn);
-                transforms.Add(transform);
-            }
-            return transforms;
-        }
     }
 }

src/Microsoft.ML.Auto/TransformInference/TransformInference.cs

@@ -117,12 +117,12 @@ public bool Equals(ColumnRoutingStructure obj)
 
         internal interface ITransformInferenceExpert
         {
-            IEnumerable<SuggestedTransform> Apply(IntermediateColumn[] columns);
+            IEnumerable<SuggestedTransform> Apply(IntermediateColumn[] columns, TaskKind task);
         }
 
         public abstract class TransformInferenceExpertBase : ITransformInferenceExpert
         {
-            public abstract IEnumerable<SuggestedTransform> Apply(IntermediateColumn[] columns);
+            public abstract IEnumerable<SuggestedTransform> Apply(IntermediateColumn[] columns, TaskKind task);
 
             protected readonly MLContext Context;
 
@@ -137,8 +137,8 @@ private static IEnumerable<ITransformInferenceExpert> GetExperts(MLContext conte
             // The expert work independently of each other, the sequence is irrelevant
             // (it only determines the sequence of resulting transforms).
 
-            // For text labels, convert to categories.
-            yield return new Experts.AutoLabel(context);
+            // For multiclass tasks, convert label column to key
+            yield return new Experts.Label(context);
 
             // For boolean columns use convert transform
             yield return new Experts.Boolean(context);
@@ -155,21 +155,26 @@ private static IEnumerable<ITransformInferenceExpert> GetExperts(MLContext conte
 
         internal static class Experts
         {
-            internal sealed class AutoLabel : TransformInferenceExpertBase
+            internal sealed class Label : TransformInferenceExpertBase
             {
-                public AutoLabel(MLContext context) : base(context)
+                public Label(MLContext context) : base(context)
                 {
                 }
 
-                public override IEnumerable<SuggestedTransform> Apply(IntermediateColumn[] columns)
+                public override IEnumerable<SuggestedTransform> Apply(IntermediateColumn[] columns, TaskKind task)
                 {
+                    if (task != TaskKind.MulticlassClassification)
+                    {
+                        yield break;
+                    }
+
                     var lastLabelColId = Array.FindLastIndex(columns, x => x.Purpose == ColumnPurpose.Label);
                     if (lastLabelColId < 0)
                         yield break;
 
                     var col = columns[lastLabelColId];
 
-                    if (col.Type.IsText())
+                    if (!col.Type.IsKey())
                     {
                         yield return ValueToKeyMappingExtension.CreateSuggestedTransform(Context, col.ColumnName, col.ColumnName);
                     }
@@ -182,7 +187,7 @@ public Categorical(MLContext context) : base(context)
                 {
                 }
 
-                public override IEnumerable<SuggestedTransform> Apply(IntermediateColumn[] columns)
+                public override IEnumerable<SuggestedTransform> Apply(IntermediateColumn[] columns, TaskKind task)
                 {
                     bool foundCat = false;
                     bool foundCatHash = false;
@@ -232,7 +237,7 @@ public Boolean(MLContext context) : base(context)
                 {
                 }
 
-                public override IEnumerable<SuggestedTransform> Apply(IntermediateColumn[] columns)
+                public override IEnumerable<SuggestedTransform> Apply(IntermediateColumn[] columns, TaskKind task)
                 {
                     var newColumns = new List<string>();
 
@@ -260,7 +265,7 @@ public Text(MLContext context) : base(context)
                 {
                 }
 
-                public override IEnumerable<SuggestedTransform> Apply(IntermediateColumn[] columns)
+                public override IEnumerable<SuggestedTransform> Apply(IntermediateColumn[] columns, TaskKind task)
                 {
                     var featureCols = new List<string>();
 
@@ -286,7 +291,7 @@ public NumericMissing(MLContext context) : base(context)
                 {
                 }
 
-                public override IEnumerable<SuggestedTransform> Apply(IntermediateColumn[] columns)
+                public override IEnumerable<SuggestedTransform> Apply(IntermediateColumn[] columns, TaskKind task)
                 {
                     var columnsWithMissing = new List<string>();
                     foreach (var column in columns)
@@ -313,7 +318,7 @@ public override IEnumerable<SuggestedTransform> Apply(IntermediateColumn[] colum
         /// <summary>
         /// Automatically infer transforms for the data view
         /// </summary>
-        public static SuggestedTransform[] InferTransforms(MLContext context, (string, DataViewType, ColumnPurpose, ColumnDimensions)[] columns)
+        public static SuggestedTransform[] InferTransforms(MLContext context, TaskKind task, (string, DataViewType, ColumnPurpose, ColumnDimensions)[] columns)
         {
             var intermediateCols = columns.Where(c => c.Item3 != ColumnPurpose.Ignore)
                 .Select(c => new IntermediateColumn(c.Item1, c.Item2, c.Item3, c.Item4))
@@ -322,7 +327,7 @@ public static SuggestedTransform[] InferTransforms(MLContext context, (string, D
             var suggestedTransforms = new List<SuggestedTransform>();
             foreach (var expert in GetExperts(context))
             {
-                SuggestedTransform[] suggestions = expert.Apply(intermediateCols).ToArray();
+                SuggestedTransform[] suggestions = expert.Apply(intermediateCols, task).ToArray();
                 suggestedTransforms.AddRange(suggestions);
             }
 

src/Microsoft.ML.Auto/TransformInference/TransformInferenceApi.cs

@@ -9,9 +9,9 @@ namespace Microsoft.ML.Auto
 {
     internal static class TransformInferenceApi
     {
-        public static IEnumerable<SuggestedTransform> InferTransforms(MLContext context, (string, DataViewType, ColumnPurpose, ColumnDimensions)[] columns)
+        public static IEnumerable<SuggestedTransform> InferTransforms(MLContext context, TaskKind task, (string, DataViewType, ColumnPurpose, ColumnDimensions)[] columns)
         {
-            return TransformInference.InferTransforms(context, columns);
+            return TransformInference.InferTransforms(context, task, columns);
         }
     }
 }

src/Microsoft.ML.Auto/Utils/MLNetUtils/ColumnTypeExtensions.cs

@@ -29,6 +29,11 @@ public static bool IsVector(this DataViewType columnType)
             return columnType is VectorType;
         }
 
+        public static bool IsKey(this DataViewType columnType)
+        {
+            return columnType is KeyType;
+        }
+
         public static bool IsKnownSizeVector(this DataViewType columnType)
         {
             var vector = columnType as VectorType;

src/Test/TransformInferenceTests.cs

@@ -645,7 +645,7 @@ public void TransformInferenceCustomLabelCol()
         }
 
         [TestMethod]
-        public void TransformInferenceCustomTextLabelCol()
+        public void TransformInferenceCustomTextLabelColMulticlass()
         {
             TransformInferenceTestCore(new (string, DataViewType, ColumnPurpose, ColumnDimensions)[]
                 {
@@ -663,7 +663,7 @@ public void TransformInferenceCustomTextLabelCol()
     ],
     ""Properties"": {}
   }
-]");
+]", TaskKind.MulticlassClassification);
         }
 
         [TestMethod]
@@ -727,9 +727,10 @@ public void TransformInferenceMissingNameCollision()
 
         private static void TransformInferenceTestCore(
             (string name, DataViewType type, ColumnPurpose purpose, ColumnDimensions dimensions)[] columns,
-            string expectedJson)
+            string expectedJson,
+            TaskKind task = TaskKind.BinaryClassification)
         {
-            var transforms = TransformInferenceApi.InferTransforms(new MLContext(), columns);
+            var transforms = TransformInferenceApi.InferTransforms(new MLContext(), task, columns);
             TestApplyTransformsToRealDataView(transforms, columns);
             var pipelineNodes = transforms.Select(t => t.PipelineNode);
             Util.AssertObjectMatchesJson(expectedJson, pipelineNodes);