Random: make clearer that SystemRandomSource.FastDoubles has low randomness properties

src/FSharp/Random.fs

@@ -37,9 +37,9 @@ module Random =
     let shared = SystemRandomSource.Default :> System.Random
 
     /// Default sampling, efficient but without custom seed (uses robust seeds internally)
-    let inline doubles (length:int) = SystemRandomSource.Doubles(length)
+    let inline doubles (length:int) = SystemRandomSource.FastDoubles(length)
     let inline doubleSeq () = SystemRandomSource.DoubleSequence()
-    let inline doubleFill (values:double[]) = SystemRandomSource.Doubles(values)
+    let inline doubleFill (values:double[]) = SystemRandomSource.FastDoubles(values)
 
     let inline doublesSeed (seed:int) (length:int) = SystemRandomSource.Doubles(length, seed)
     let inline doubleSeqSeed (seed:int) = SystemRandomSource.DoubleSequence(seed)

src/Numerics/Generate.cs

@@ -546,7 +546,7 @@ namespace MathNet.Numerics
         /// </summary>
         public static double[] Uniform(int length)
         {
-            return SystemRandomSource.Doubles(length);
+            return SystemRandomSource.FastDoubles(length);
         }
 
         /// <summary>
@@ -565,7 +565,7 @@ namespace MathNet.Numerics
         /// </summary>
         public static T[] UniformMap<T>(int length, Func<double, T> map)
         {
-            var samples = SystemRandomSource.Doubles(length);
+            var samples = SystemRandomSource.FastDoubles(length);
             var data = new T[length];
             for (int i = 0; i < data.Length; i++)
             {
@@ -589,8 +589,8 @@ namespace MathNet.Numerics
         /// </summary>
         public static T[] UniformMap2<T>(int length, Func<double, double, T> map)
         {
-            var samples1 = SystemRandomSource.Doubles(length);
+            var samples1 = SystemRandomSource.FastDoubles(length);
-            var samples2 = SystemRandomSource.Doubles(length);
+            var samples2 = SystemRandomSource.FastDoubles(length);
             var data = new T[length];
             for (int i = 0; i < data.Length; i++)
             {

src/Numerics/Random/SystemRandomSource.cs

@@ -124,9 +124,10 @@ namespace MathNet.Numerics.Random
 
         /// <summary>
         /// Fill an array with uniform random numbers greater than or equal to 0.0 and less than 1.0.
+        /// WARNING: potentially very short random sequence length, can generate repeated partial sequences.
         /// </summary>
         /// <remarks>Parallelized on large length, but also supports being called in parallel from multiple threads</remarks>
-        public static void Doubles(double[] values)
+        public static void FastDoubles(double[] values)
         {
             if (values.Length < 2048)
             {
@@ -146,13 +147,14 @@ namespace MathNet.Numerics.Random
 
         /// <summary>
         /// Returns an array of uniform random numbers greater than or equal to 0.0 and less than 1.0.
+        /// WARNING: potentially very short random sequence length, can generate repeated partial sequences.
         /// </summary>
         /// <remarks>Parallelized on large length, but also supports being called in parallel from multiple threads</remarks>
         [TargetedPatchingOptOut("Performance critical to inline this type of method across NGen image boundaries")]
-        public static double[] Doubles(int length)
+        public static double[] FastDoubles(int length)
         {
             var data = new double[length];
-            Doubles(data);
+            FastDoubles(data);
             return data;
         }