Changed List to HashSet to ensure that there are no duplicates

Author: ross-p-smith

src/Microsoft.ML.Core/Prediction/ISweeper.cs

@@ -174,6 +174,11 @@ public override string ToString()
         {
             return string.Join(" ", _parameterValues.Select(kvp => string.Format("{0}={1}", kvp.Value.Name, kvp.Value.ValueText)).ToArray());
         }
+
+        public override int GetHashCode()
+        {
+            return _hash;
+        }
     }
 
     /// <summary>

src/Microsoft.ML.Sweeper/Algorithms/Grid.cs

@@ -67,7 +67,7 @@ protected SweeperBase(ArgumentsBase args, IHostEnvironment env, IValueGenerator[
         public virtual ParameterSet[] ProposeSweeps(int maxSweeps, IEnumerable<IRunResult> previousRuns = null)
         {
             var prevParamSets = previousRuns?.Select(r => r.ParameterSet).ToList() ?? new List<ParameterSet>();
-            var result = new List<ParameterSet>();
+            var result = new HashSet<ParameterSet>();
             for (int i = 0; i < maxSweeps; i++)
             {
                 ParameterSet paramSet;
@@ -150,12 +150,12 @@ public RandomGridSweeper(IHostEnvironment env, Arguments args, IValueGenerator[]
             }
         }
 
-        public override ParameterSet[] ProposeSweeps(int maxSweeps, IEnumerable<IRunResult> previousRuns)
+        public override ParameterSet[] ProposeSweeps(int maxSweeps, IEnumerable<IRunResult> previousRuns = null)
         {
             if (_nGridPoints == 0)
                 return base.ProposeSweeps(maxSweeps, previousRuns);
 
-            var result = new List<ParameterSet>();
+            var result = new HashSet<ParameterSet>();
             var prevParamSets = (previousRuns != null)
                 ? previousRuns.Select(r => r.ParameterSet).ToList()
                 : new List<ParameterSet>();

test/Microsoft.ML.Sweeper.Tests/SweeperTest.cs

@@ -12,21 +12,54 @@ namespace Microsoft.ML.Sweeper.Tests
     public class SweeperTest
     {
         [Fact]
-        public void SweeperReturnsDistinctValues()
+        public void UniformRandomSweeperReturnsDistinctValuesWhenProposeSweep()
         {
-            var args = new DiscreteParamArguments();
-            args.Name = "Amazing";
-            args.Values = new string[] { "one" };
-            var valueGenerator = new DiscreteValueGenerator(args);
+            DiscreteValueGenerator valueGenerator = CreateDiscreteValueGenerator();
+
             using (var writer = new StreamWriter(new MemoryStream()))
             using (var env = new TlcEnvironment(42, outWriter: writer, errWriter: writer))
             {
-                var sweeper = new UniformRandomSweeper(env, new SweeperBase.ArgumentsBase(), new[] { valueGenerator });
-                var results = sweeper.ProposeSweeps(2);
+                var sweeper = new UniformRandomSweeper(env,
+                    new SweeperBase.ArgumentsBase(),
+                    new[] { valueGenerator });
+
+                var results = sweeper.ProposeSweeps(5000);
                 Assert.NotNull(results);
+
                 int length = results.Length;
-                Assert.Equal(1, length);
+                Assert.Equal(2, length);
             }
         }
+
+        [Fact]
+        public void RandomGridSweeperReturnsDistinctValuesWhenProposeSweep()
+        {
+            DiscreteValueGenerator valueGenerator = CreateDiscreteValueGenerator();
+
+            using (var writer = new StreamWriter(new MemoryStream()))
+            using (var env = new TlcEnvironment(42, outWriter: writer, errWriter: writer))
+            {
+                var sweeper = new RandomGridSweeper(env,
+                    new RandomGridSweeper.Arguments(),
+                    new[] { valueGenerator });
+
+                var results = sweeper.ProposeSweeps(5000);
+                Assert.NotNull(results);
+
+                int length = results.Length;
+                Assert.Equal(2, length);
+            }
+        }
+
+        private static DiscreteValueGenerator CreateDiscreteValueGenerator()
+        {
+            var args = new DiscreteParamArguments()
+            {
+                Name = "TestParam",
+                Values = new string[] { "one", "two" }
+            };
+
+            return new DiscreteValueGenerator(args);
+        }
     }
 }