Bail to default implementation upon any unforeseen situation

src/Microsoft.ML.FastTree/RandomForestClassification.cs

@@ -265,7 +265,15 @@ public static extern unsafe int DecisionForestClassificationCompute(
         [BestFriend]
         private bool IsDispatchingToOneDalEnabled()
         {
-            return OneDalUtils.IsDispatchingEnabled();
+            try
+            {
+                return OneDalUtils.IsDispatchingEnabled();
+            }
+            catch (Exception)
+            {
+                // Bail to default implementation upon encountering any situation where dispatch failed
+                return false;
+            }
         }
 
         [BestFriend]

src/Microsoft.ML.FastTree/RandomForestRegression.cs

@@ -398,7 +398,15 @@ public static extern unsafe int DecisionForestRegressionCompute(
         [BestFriend]
         private bool IsDispatchingToOneDalEnabled()
         {
-            return OneDalUtils.IsDispatchingEnabled();
+            try
+            {
+                return OneDalUtils.IsDispatchingEnabled();
+            }
+            catch (Exception)
+            {
+                // fall back to original implementation for any circumstance that prevents dispatching
+                return false;
+            }
         }
 
         [BestFriend]

src/Microsoft.ML.Mkl.Components/OlsLinearRegression.cs

@@ -14,9 +14,9 @@
 using Microsoft.ML.Internal.Internallearn;
 using Microsoft.ML.Internal.Utilities;
 using Microsoft.ML.Model;
+using Microsoft.ML.OneDal;
 using Microsoft.ML.Runtime;
 using Microsoft.ML.Trainers;
-using Microsoft.ML.OneDal;
 
 [assembly: LoadableClass(OlsTrainer.Summary, typeof(OlsTrainer), typeof(OlsTrainer.Options),
     new[] { typeof(SignatureRegressorTrainer), typeof(SignatureTrainer), typeof(SignatureFeatureScorerTrainer) },
@@ -409,7 +409,15 @@ private void ComputeMklRegression(IChannel ch, FloatLabelCursor.Factory cursorFa
         [BestFriend]
         private bool IsDispatchingToOneDalEnabled()
         {
-            return OneDalUtils.IsDispatchingEnabled();
+            try
+            {
+                return OneDalUtils.IsDispatchingEnabled();
+            }
+            catch (Exception)
+            {
+                // Bail to default implementation upon any situation that prevents dispatching
+                return false;
+            }
         }
 
         private OlsModelParameters TrainCore(IChannel ch, FloatLabelCursor.Factory cursorFactory, int featureCount)

src/Microsoft.ML.OneDal/OneDalUtils.cs

@@ -3,8 +3,8 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
-using System.IO;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using System.Runtime.InteropServices;
 using Microsoft.ML.Internal.Utilities;
@@ -17,14 +17,6 @@ namespace Microsoft.ML.OneDal
     internal static class OneDalUtils
     {
 
-#if false
-        [BestFriend]
-        internal static bool IsDispatchingEnabled()
-        {
-            return Environment.GetEnvironmentVariable("MLNET_BACKEND") == "ONEDAL" &&
-                System.Runtime.InteropServices.RuntimeInformation.ProcessArchitecture == System.Runtime.InteropServices.Architecture.X64;
-        }
-#else
         [BestFriend]
         internal static bool IsDispatchingEnabled()
         {
@@ -47,7 +39,6 @@ internal static bool IsDispatchingEnabled()
             }
             return false;
         }
-#endif
 
         [BestFriend]
         internal static long GetTrainData(IChannel channel, FloatLabelCursor.Factory cursorFactory, ref List<float> featuresList, ref List<float> labelsList, int numberOfFeatures)