Add helper for faster creation of objects of generic type

src/Runtime/Core/Utils/Util.cs

@@ -6,16 +6,13 @@ using System;
 using System.Collections.Generic;
 using System.Reflection;
 using System.Text;
-using System.IO;
-using System.Globalization;
 using Microsoft.ML.Probabilistic.Collections;
 using Microsoft.ML.Probabilistic.Math;
-using System.Xml;
-using System.Xml.Schema;
 
 namespace Microsoft.ML.Probabilistic.Utilities
 {
     using System.Linq;
+    using System.Linq.Expressions;
 
 #if SUPPRESS_XMLDOC_WARNINGS
 #pragma warning disable 1591
@@ -464,6 +461,23 @@ namespace Microsoft.ML.Probabilistic.Utilities
 
             yield break;
         }
+
+        /// <summary>
+        /// A faster versio of `new T()` when T is a generic type parameter.
+        /// See: https://stackoverflow.com/a/1280832
+        /// </summary>
+        public static T New<T>()
+            where T : new()
+        {
+            return NewFuncCache<T>.NewFunc();
+        }
+
+        private static class NewFuncCache<T>
+            where T : new()
+        {
+            public static Expression<Func<T>> NewExpression = () => new T();
+            public static Func<T> NewFunc = NewExpression.Compile();
+        }
     }
 
 #if SUPPRESS_XMLDOC_WARNINGS

src/Runtime/Distributions/Automata/Automaton.Builder.cs

@@ -9,6 +9,7 @@ namespace Microsoft.ML.Probabilistic.Distributions.Automata
     using System.Diagnostics;
 
     using Microsoft.ML.Probabilistic.Collections;
+    using Microsoft.ML.Probabilistic.Utilities;
 
     public abstract partial class Automaton<TSequence, TElement, TElementDistribution, TSequenceManipulator, TThis>
     {
@@ -428,7 +429,12 @@ namespace Microsoft.ML.Probabilistic.Distributions.Automata
             /// <summary>
             /// Builds new automaton object. Builder must not be used after this method is called
             /// </summary>
-            public TThis GetAutomaton() => new TThis() { Data = this.GetData() };
+            public TThis GetAutomaton()
+            {
+                var result = Util.New<TThis>();
+                result.Data = this.GetData();
+                return result;
+            }
 
             /// <summary>
             /// Stores built automaton in pre-allocated <see cref="Automaton{TSequence,TElement,TElementDistribution,TSequenceManipulator,TThis}"/> object.

src/Runtime/Distributions/Automata/Automaton.cs

@@ -321,7 +321,9 @@ namespace Microsoft.ML.Probabilistic.Distributions.Automata
                 builder.Start.AddTransition(allowedElements, Weight.FromLogValue(-allowedElements.GetLogAverageOf(allowedElements)), builder.StartStateIndex);
             }
 
-            return new TThis() { Data = builder.GetData(true) };
+            var result = Util.New<TThis>();
+            result.Data = builder.GetData(true);
+            return result;
         }
 
         /// <summary>
@@ -348,15 +350,17 @@ namespace Microsoft.ML.Probabilistic.Distributions.Automata
         {
             Argument.CheckIfNotNull(allowedElements, nameof(allowedElements));
 
-            var result = new Builder();
+            var builder = new Builder();
             if (!double.IsNegativeInfinity(logValue))
             {
                 allowedElements = allowedElements.CreatePartialUniform();
-                var finish = result.Start.AddTransition(allowedElements, Weight.FromLogValue(-allowedElements.GetLogAverageOf(allowedElements)));
+                var finish = builder.Start.AddTransition(allowedElements, Weight.FromLogValue(-allowedElements.GetLogAverageOf(allowedElements)));
                 finish.SetEndWeight(Weight.FromLogValue(logValue));
             }
 
-            return new TThis() { Data = result.GetData(true) };
+            var result = Util.New<TThis>();
+            result.Data = builder.GetData(true);
+            return result;
         }
 
         /// <summary>
@@ -400,19 +404,21 @@ namespace Microsoft.ML.Probabilistic.Distributions.Automata
         {
             Argument.CheckIfNotNull(sequences, "sequences");
 
-            var result = new Builder();
+            var builder = new Builder();
             int sequenceCount = 0;
             if (!double.IsNegativeInfinity(logValue))
             {
                 foreach (var sequence in sequences)
                 {
-                    var sequenceEndState = result.Start.AddTransitionsForSequence(sequence);
+                    var sequenceEndState = builder.Start.AddTransitionsForSequence(sequence);
                     sequenceEndState.SetEndWeight(Weight.FromLogValue(logValue));
                     ++sequenceCount;
                 }
             }
 
-            return new TThis() { Data = result.GetData(sequenceCount <= 1 ? (bool?)true : null) };
+            var result = Util.New<TThis>();
+            result.Data = builder.GetData(sequenceCount <= 1 ? (bool?)true : null);
+            return result;
         }
 
         /// <summary>
@@ -1262,7 +1268,8 @@ namespace Microsoft.ML.Probabilistic.Distributions.Automata
                 }
             }
 
-            automaton = new TThis() { Data = result.GetData(true) };
+            automaton = Util.New<TThis>();
+            automaton.Data = result.GetData(true);
             return true;
         }
 
@@ -1477,7 +1484,8 @@ namespace Microsoft.ML.Probabilistic.Distributions.Automata
             var bothInputsDeterminized = automaton1.Data.IsDeterminized == true && automaton2.Data.IsDeterminized == true;
             var determinizationState = bothInputsDeterminized ? (bool?)true : null;
 
-            var result = new TThis() { Data = builder.GetData(determinizationState) };
+            var result = Util.New<TThis>();
+            result.Data = builder.GetData(determinizationState);
             if (determinizationState != true && result is StringAutomaton && tryDeterminize)
             {
                 result = result.TryDeterminize();
@@ -2141,36 +2149,42 @@ namespace Microsoft.ML.Probabilistic.Distributions.Automata
 
         #region Helpers
 
-        protected TThis WithData(DataContainer data) => new TThis()
+        protected TThis WithData(DataContainer data)
         {
-            Data = data,
-            LogValueOverride = LogValueOverride,
-            PruneStatesWithLogEndWeightLessThan = PruneStatesWithLogEndWeightLessThan
-        };
+            var result = Util.New<TThis>();
+            result.Data = data;
+            result.LogValueOverride = LogValueOverride;
+            result.PruneStatesWithLogEndWeightLessThan = PruneStatesWithLogEndWeightLessThan;
+            return result;
+        }
 
         /// <summary>
         /// Creates a copy of the current automaton with a different value of <see cref="LogValueOverride"/>.
         /// </summary>
         /// <param name="logValueOverride">New <see cref="LogValueOverride"/>.</param>
         /// <returns>The created automaton.</returns>
-        public TThis WithLogValueOverride(double? logValueOverride) => new TThis()
+        public TThis WithLogValueOverride(double? logValueOverride)
         {
-            Data = Data,
-            LogValueOverride = logValueOverride,
-            PruneStatesWithLogEndWeightLessThan = PruneStatesWithLogEndWeightLessThan
-        };
+            var result = Util.New<TThis>();
+            result.Data = Data;
+            result.LogValueOverride = logValueOverride;
+            result.PruneStatesWithLogEndWeightLessThan = PruneStatesWithLogEndWeightLessThan;
+            return result;
+        }
 
         /// <summary>
         /// Creates a copy of the current automaton with a different value of <see cref="PruneStatesWithLogEndWeightLessThan"/>.
         /// </summary>
         /// <param name="pruneStatesWithLogEndWeightLessThan">New <see cref="PruneStatesWithLogEndWeightLessThan"/>.</param>
         /// <returns>The created automaton.</returns>
-        public TThis WithPruneStatesWithLogEndWeightLessThan(double? pruneStatesWithLogEndWeightLessThan) => new TThis()
+        public TThis WithPruneStatesWithLogEndWeightLessThan(double? pruneStatesWithLogEndWeightLessThan)
         {
-            Data = Data,
-            LogValueOverride = LogValueOverride,
-            PruneStatesWithLogEndWeightLessThan = pruneStatesWithLogEndWeightLessThan
-        };
+            var result = Util.New<TThis>();
+            result.Data = Data;
+            result.LogValueOverride = LogValueOverride;
+            result.PruneStatesWithLogEndWeightLessThan = pruneStatesWithLogEndWeightLessThan;
+            return result;
+        }
 
         /// <summary>
         /// Gets a value indicating how close two given automata are

src/Runtime/Distributions/Automata/StringAutomaton.cs

@@ -2,15 +2,12 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using Microsoft.ML.Probabilistic.Collections;
-
 namespace Microsoft.ML.Probabilistic.Distributions.Automata
 {
     using System;
     using System.Collections.Generic;
-    using System.Diagnostics;
     using System.IO;
-    using System.Linq;
+   
 
     /// <summary>
     /// Represents a weighted finite state automaton defined on <see cref="string"/>.

src/Runtime/Distributions/Automata/WeightFunctions.DictionaryWeightFunction.cs

@@ -59,7 +59,7 @@ namespace Microsoft.ML.Probabilistic.Distributions.Automata
             /// <param name="sequenceWeightPairs">The collection of pairs of a sequence and the weight on that sequence.</param>
             public static TThis FromWeights(IEnumerable<KeyValuePair<TSequence, Weight>> sequenceWeightPairs)
             {
-                var result = new TThis();
+                var result = Util.New<TThis>();
                 result.SetWeights(sequenceWeightPairs);
                 return result;
 
@@ -73,7 +73,7 @@ namespace Microsoft.ML.Probabilistic.Distributions.Automata
             [Construction(nameof(Dictionary))]
             public static TThis FromDistinctWeights(IEnumerable<KeyValuePair<TSequence, Weight>> sequenceWeightPairs)
             {
-                var result = new TThis();
+                var result = Util.New<TThis>();
                 result.SetDistinctWeights(sequenceWeightPairs);
                 return result;
             }
@@ -100,7 +100,7 @@ namespace Microsoft.ML.Probabilistic.Distributions.Automata
             /// <param name="point">The only sequence contained in the dictionary.</param>
             public static TThis FromPoint(TSequence point)
             {
-                var result = new TThis();
+                var result = Util.New<TThis>();
                 result.SetDistinctWeights(new[] { new KeyValuePair<TSequence, Weight>(point, Weight.One) });
                 return result;
             }

src/Runtime/Distributions/SequenceDistribution.cs

@@ -65,7 +65,7 @@ namespace Microsoft.ML.Probabilistic.Distributions
         /// A function mapping sequences to weights (non-normalized probabilities).
         /// </summary>
         [DataMember]
-        private TWeightFunction sequenceToWeight = new TWeightFunction();
+        private TWeightFunction sequenceToWeight = default;
 
         /// <summary>
         /// Specifies whether the <see cref="sequenceToWeight"/> is normalized.
@@ -142,7 +142,9 @@ namespace Microsoft.ML.Probabilistic.Distributions
         {
             Argument.CheckIfNotNull(point, "point", "Point mass must not be null.");
 
-            return new TThis { Point = point };
+            var result = Util.New<TThis>();
+            result.Point = point;
+            return result;
         }
 
         /// <summary>
@@ -153,7 +155,7 @@ namespace Microsoft.ML.Probabilistic.Distributions
         [Skip]
         public static TThis Uniform()
         {
-            var result = new TThis();
+            var result = Util.New<TThis>();
             result.SetToUniform();
             return result;
         }
@@ -165,7 +167,7 @@ namespace Microsoft.ML.Probabilistic.Distributions
         [Construction(UseWhen = "IsZero")]
         public static TThis Zero()
         {
-            var result = new TThis();
+            var result = Util.New<TThis>();
             result.SetToZero();
             return result;
         }
@@ -180,7 +182,7 @@ namespace Microsoft.ML.Probabilistic.Distributions
         {
             Argument.CheckIfNotNull(weightFunction, nameof(weightFunction));
 
-            var result = new TThis();
+            var result = Util.New<TThis>();
             result.SetWeightFunction(weightFunction);
             return result;
         }
@@ -293,7 +295,7 @@ namespace Microsoft.ML.Probabilistic.Distributions
             }
 
             var probFunctions = enumerable.Select(d => d.sequenceToWeight);
-            var result = new TThis();
+            var result = Util.New<TThis>();
             result.sequenceToWeight = WeightFunctionFactory.Sum(probFunctions).NormalizeStructure();
             return result;
         }
@@ -318,7 +320,7 @@ namespace Microsoft.ML.Probabilistic.Distributions
         /// <returns>The created mixture distribution.</returns>
         public static TThis OneOf(double weight1, TThis dist1, double weight2, TThis dist2)
         {
-            var result = new TThis();
+            var result = Util.New<TThis>();
             result.SetToSum(weight1, dist1, weight2, dist2);
             return result;
         }
@@ -331,7 +333,7 @@ namespace Microsoft.ML.Probabilistic.Distributions
         /// <returns>The created distribution.</returns>
         public static TThis OneOf(IEnumerable<KeyValuePair<TSequence, double>> sequenceProbPairs)
         {
-            var result = new TThis();
+            var result = Util.New<TThis>();
             result.sequenceToWeight = WeightFunctionFactory.FromValues(sequenceProbPairs).NormalizeStructure();
             return result;
         }
@@ -1111,9 +1113,9 @@ namespace Microsoft.ML.Probabilistic.Distributions
         {
             Argument.CheckIfNotNull(that, "that");
 
-            var auto = new TThis();
-            auto.SetToProduct((TThis)this, that);
-            return auto;
+            var result = Util.New<TThis>();
+            result.SetToProduct((TThis)this, that);
+            return result;
         }
 
         /// <summary>
@@ -1157,8 +1159,8 @@ namespace Microsoft.ML.Probabilistic.Distributions
         {
             Argument.CheckIfNotNull(that, nameof(that));
 
-            var temp = new TThis();
-            return temp.SetToProductAndReturnLogNormalizer((TThis)this, that, false);
+            var result = Util.New<TThis>();
+            return result.SetToProductAndReturnLogNormalizer((TThis)this, that, false);
         }
 
         /// <summary>
@@ -1319,7 +1321,7 @@ namespace Microsoft.ML.Probabilistic.Distributions
         /// <returns>The created copy.</returns>
         public TThis Clone()
         {
-            var result = new TThis();
+            var result = Util.New<TThis>();
             result.SetTo((TThis)this);
             return result;
         }
@@ -1619,7 +1621,7 @@ namespace Microsoft.ML.Probabilistic.Distributions
         /// <returns>The created distribution.</returns>
         protected static TThis UniformOf(TElementDistribution allowedElements, double uniformLogProb)
         {
-            var result = new TThis();
+            var result = Util.New<TThis>();
             result.SetToUniformOf(allowedElements, uniformLogProb);
             return result;
         }