From d8ef0310df16d2895513089a5b062c35dc353cb5 Mon Sep 17 00:00:00 2001
From: inga-lovinde <52715130+inga-lovinde@users.noreply.github.com>
Date: Sun, 16 Apr 2017 02:21:40 +0300
Subject: [PATCH] Memory usage optimized

---
 dotnet/WhiteRabbit/PhraseSet.cs               |  5 +--
 .../PrecomputedPermutationsGenerator.cs       | 33 +++++++++++++++----
 2 files changed, 29 insertions(+), 9 deletions(-)

diff --git a/dotnet/WhiteRabbit/PhraseSet.cs b/dotnet/WhiteRabbit/PhraseSet.cs
index 667bfcf..642f68e 100644
--- a/dotnet/WhiteRabbit/PhraseSet.cs
+++ b/dotnet/WhiteRabbit/PhraseSet.cs
@@ -7,7 +7,7 @@
     {
         public fixed long Buffer[4 * Constants.PhrasesPerSet];
 
-        public PhraseSet(Word[] words, int[][] permutations, int offset, int numberOfCharacters)
+        public PhraseSet(Word[] words, long[] permutations, int offset, int numberOfCharacters)
         {
             Debug.Assert(numberOfCharacters + words.Length - 1 < 27);
 
@@ -21,7 +21,8 @@
                     var cumulativeWordOffsetX4 = 0;
                     for (var j = 0; j < numberOfWords; j++)
                     {
-                        var currentWord = words[permutation[j]];
+                        var currentWord = words[permutation & 15];
+                        permutation = permutation >> 4;
                         longBuffer[0] |= currentWord.Buffers[cumulativeWordOffsetX4 + 0];
                         longBuffer[1] |= currentWord.Buffers[cumulativeWordOffsetX4 + 1];
                         longBuffer[2] ^= currentWord.Buffers[cumulativeWordOffsetX4 + 2];
diff --git a/dotnet/WhiteRabbit/PrecomputedPermutationsGenerator.cs b/dotnet/WhiteRabbit/PrecomputedPermutationsGenerator.cs
index b2c9f66..669c732 100644
--- a/dotnet/WhiteRabbit/PrecomputedPermutationsGenerator.cs
+++ b/dotnet/WhiteRabbit/PrecomputedPermutationsGenerator.cs
@@ -5,25 +5,44 @@
 
     internal static class PrecomputedPermutationsGenerator
     {
-        private static int[][][] Permutations { get; } = Enumerable.Range(0, 9).Select(GeneratePermutations).ToArray();
+        private static long[][] Permutations { get; } = Enumerable.Range(0, 9).Select(GeneratePermutations).ToArray();
 
         private static long[] PermutationsNumbers { get; } = GeneratePermutationsNumbers().Take(19).ToArray();
 
-        public static int[][] HamiltonianPermutations(int n) => Permutations[n];
+        public static long[] HamiltonianPermutations(int n) => Permutations[n];
 
         public static long GetPermutationsNumber(int n) => PermutationsNumbers[n];
 
-        private static int[][] GeneratePermutations(int n)
+        private static long[] GeneratePermutations(int n)
         {
             var result = PermutationsGenerator.HamiltonianPermutations(n)
-                .Select(permutation => permutation.PermutationData)
+                .Select(FormatPermutation)
                 .ToArray();
-            if (result.Length % Constants.PhrasesPerSet == 0)
+
+            return PadToWholeChunks(result, Constants.PhrasesPerSet);
+        }
+
+        private static T[] PadToWholeChunks<T>(T[] original, int chunkSize)
+        {
+            if (original.Length % chunkSize == 0)
+            {
+                return original;
+            }
+
+            return original.Concat(Enumerable.Repeat(original[0], chunkSize - (original.Length % chunkSize))).ToArray();
+        }
+
+        private static long FormatPermutation(PermutationsGenerator.Permutation permutation)
+        {
+            System.Diagnostics.Debug.Assert(permutation.PermutationData.Length <= 16);
+
+            long result = 0;
+            for (var i = 0; i < permutation.PermutationData.Length; i++)
             {
-                return result;
+                result |= (long)(permutation.PermutationData[i]) << (4 * i);
             }
 
-            return result.Concat(Enumerable.Repeat(result[0], Constants.PhrasesPerSet - (result.Length % Constants.PhrasesPerSet))).ToArray();
+            return result;
         }
 
         private static IEnumerable<long> GeneratePermutationsNumbers()