AutoML.Net filter infinity value when calculate average score (#5345)

* fix 5339

* Update CrossValSummaryRunner.cs

Co-authored-by: BigBigMiao <BigBigMiao@github.com>

Author: LittleLittleCloud

src/Microsoft.ML.AutoML/Experiment/Runners/CrossValSummaryRunner.cs

@@ -157,13 +157,24 @@ private static double GetAverageOfNonNaNScores(IEnumerable<double> results)
             return newResults.Average(r => r);
         }
 
+        /// <summary>
+        /// return the index of value from <paramref name="values"/> that closest to <paramref name="average"/>. If <paramref name="average"/> is NaN, +/- inf, the first, max/min value's index will be return.
+        /// </summary>
         private static int GetIndexClosestToAverage(IEnumerable<double> values, double average)
         {
             // Average will be NaN iff all values are NaN.
             // Return the first index in this case.
             if (double.IsNaN(average))
                 return 0;
 
+            // Return the max value's index if average is positive inf.
+            if (double.IsPositiveInfinity(average))
+                return values.ToList().IndexOf(values.Max());
+
+            // Return the min value's index if average is negative inf.
+            if (double.IsNegativeInfinity(average))
+                return values.ToList().IndexOf(values.Min());
+
             int avgFoldIndex = -1;
             var smallestDistFromAvg = double.PositiveInfinity;
             for (var i = 0; i < values.Count(); i++)
@@ -181,4 +192,4 @@ private static int GetIndexClosestToAverage(IEnumerable<double> values, double a
             return avgFoldIndex;
         }
     }
-}
+}