If users force HashSet, try perfect hashset

Author: Genbox

Src/FastData/FastDataGenerator.cs

@@ -151,7 +151,14 @@ private static IEnumerable<IStructure<T>> GetDataStructureCandidates<T>(T[] data
         else if (ds == StructureType.BinarySearch)
             yield return new BinarySearchStructure<T>(props.DataType, DefaultStringComparison);
         else if (ds == StructureType.HashSet)
-            yield return new HashSetChainStructure<T>(HashData.Create(data, props.DataType, config.HashCapacityFactor));
+        {
+            HashData hashData = HashData.Create(data, props.DataType, config.HashCapacityFactor);
+
+            if (hashData.HashCodesPerfect)
+                yield return new HashSetPerfectStructure<T>(hashData);
+
+            yield return new HashSetChainStructure<T>(hashData);
+        }
         else
             throw new InvalidOperationException($"Unsupported DataStructure {ds}");
     }