diff --git a/CHANGELOG.md b/CHANGELOG.md
index f59449e..4775c6c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 ### Change Log
 
+#### 1.6.0
+
+* Optimise ranking flushes.
+
 #### 1.5.0
 
 * Static interface.
diff --git a/CMakeLists.txt b/CMakeLists.txt
index a915c26..7fb4d48 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -5,7 +5,7 @@ project(${PROJECT_NAME})
 
 # Versioning.
 set(SK_POKER_EVAL_VERSION_MAJOR 1)
-set(SK_POKER_EVAL_VERSION_MINOR 5)
+set(SK_POKER_EVAL_VERSION_MINOR 6)
 set(SK_POKER_EVAL_VERSION_PATCH 0)
 
 # Get the current commit.
diff --git a/README.md b/README.md
index e805eee..c358699 100644
--- a/README.md
+++ b/README.md
@@ -6,9 +6,9 @@ A lightweight 32-bit Texas Hold'em 7-card hand evaluator written in C++.
 
 [![Build Status](https://travis-ci.org/kennethshackleton/SKPokerEval.svg)](https://travis-ci.org/kennethshackleton/SKPokerEval)
 
-## Example
+## How do I use it?
 
-```
+```cpp
 #include <iostream>
 #include "SevenEval.h"
 
@@ -18,3 +18,25 @@ int main() {
   return 0;
 }
 ```
+
+## Why does it work?
+
+We exploit a key-scheme that gives us just enough uniqueness to correctly identify the integral rank of any 7-card hand, where the greater this rank is the better the hand we hold and two hands of the same rank always draw. Typically we require six additions and a memory footprint just shy of 400kB.
+
+To start with we computed by brute force the first thirteen non-negative integers such that the sum of exactly seven with each taken at most four times is unique among all such sums: 0, 1, 5, 22, 98, 453, 2031, 8698, 22854, 83661, 262349, 636345 and 1479181. A valid sum might be 0+0+1+1+1+1+5 = 9 or 0+98+98+453+98+98+1 = 846, but invalid sum expressions include 0+262349+0+0+0+1 (too few summands), 1+1+5+22+98+453+2031+8698 (too many summands), 0+1+5+22+98+453+2031+8698 (again too many summands, although 1+5+22+98+453+2031+8698 is a legitimate expression) and 1+1+1+1+1+98+98 (too many 1's). We assign these integers as the card face values and add these together to generate a key for any non-flush 7-card hand. The largest non-flush key we see is 7825759, corresponding to any of the four quad-of-aces-full-of-kings.
+
+Similarly, we assign the integer values 0, 1, 8 and 57 for spade, heart, diamond and club respectively. Any sum of exactly seven values taken from {0, 1, 8, 57} is unique among all such sums. We add up the suits of a 7-card hand to produce a "flush check" key and use this to find a pre-calculated flush suit value (in the case we're looking at a flush) or otherwise a defined non-flush constant. The largest flush key we see is 7999, corresponding to any of the four 7-card straight flushes with ace high.
+
+The extraordinarily lucky aspect of this is that the maximum non-flush key we have, 7825759, is a 23-bit integer (note 2^23 = 8388608) and the largest suit key we find, 57*7 = 399, is a 9-bit integer (note 2^9 = 512). If we bit-shift a card's non-flush face value and add to this its flush check to make a card key in advance, when we aggregate the resulting card keys over a given 7-card hand we generate a 23+9 = 32-bit integer key for the whole hand. This integer key can only just be accommodated on a 32-bit machine and yet still carries enough information to decide if we're looking at a flush and if not to then look up the rank of the hand.
+
+## How might I profile my contribution?
+
+The project contains a [profiler](src/Profiler.cpp) which might be used to help benchmark your changes.
+
+```bash
+g++ -c -std=c++11 -O3 Profiler.cpp
+g++ -o profile Profiler.o
+./profile
+```
+
+Crudely, the lower the result the more efficiently the ranks were computed. This starts to be compelling with consistent gains of, say, 30% or more.
diff --git a/src/Constants.h b/src/Constants.h
index 6764210..d82743f 100644
--- a/src/Constants.h
+++ b/src/Constants.h
@@ -30,6 +30,11 @@
 #define DIAMOND 8
 #define CLUB 57
 
+#define INDEX_SPADE 0
+#define INDEX_HEART 1
+#define INDEX_DIAMOND 2
+#define INDEX_CLUB 3
+
 #define TWO_FIVE 0
 #define THREE_FIVE 1
 #define FOUR_FIVE 5
diff --git a/src/Deckcards.h b/src/Deckcards.h
index 80b9944..889e21a 100644
--- a/src/Deckcards.h
+++ b/src/Deckcards.h
@@ -23,7 +23,7 @@
 #include "Constants.h"
 #include <cstdint>
 
-uint32_t const card[DECK_SIZE] = {
+uint_fast32_t const card[DECK_SIZE] = {
   (ACE << NON_FLUSH_BIT_SHIFT) + SPADE,
   (ACE << NON_FLUSH_BIT_SHIFT) + HEART,
   (ACE << NON_FLUSH_BIT_SHIFT) + DIAMOND,
@@ -90,23 +90,23 @@ uint32_t const card[DECK_SIZE] = {
   (TWO << NON_FLUSH_BIT_SHIFT) + CLUB
 };
 
-uint16_t const suit[DECK_SIZE] = {
-  SPADE, HEART, DIAMOND, CLUB,
-  SPADE, HEART, DIAMOND, CLUB,
-  SPADE, HEART, DIAMOND, CLUB,
-  SPADE, HEART, DIAMOND, CLUB,
-  SPADE, HEART, DIAMOND, CLUB,
-  SPADE, HEART, DIAMOND, CLUB,
-  SPADE, HEART, DIAMOND, CLUB,
-  SPADE, HEART, DIAMOND, CLUB,
-  SPADE, HEART, DIAMOND, CLUB,
-  SPADE, HEART, DIAMOND, CLUB,
-  SPADE, HEART, DIAMOND, CLUB,
-  SPADE, HEART, DIAMOND, CLUB,
-  SPADE, HEART, DIAMOND, CLUB
+uint_fast8_t const suit[DECK_SIZE] = {
+  INDEX_SPADE, INDEX_HEART, INDEX_DIAMOND, INDEX_CLUB,
+  INDEX_SPADE, INDEX_HEART, INDEX_DIAMOND, INDEX_CLUB,
+  INDEX_SPADE, INDEX_HEART, INDEX_DIAMOND, INDEX_CLUB,
+  INDEX_SPADE, INDEX_HEART, INDEX_DIAMOND, INDEX_CLUB,
+  INDEX_SPADE, INDEX_HEART, INDEX_DIAMOND, INDEX_CLUB,
+  INDEX_SPADE, INDEX_HEART, INDEX_DIAMOND, INDEX_CLUB,
+  INDEX_SPADE, INDEX_HEART, INDEX_DIAMOND, INDEX_CLUB,
+  INDEX_SPADE, INDEX_HEART, INDEX_DIAMOND, INDEX_CLUB,
+  INDEX_SPADE, INDEX_HEART, INDEX_DIAMOND, INDEX_CLUB,
+  INDEX_SPADE, INDEX_HEART, INDEX_DIAMOND, INDEX_CLUB,
+  INDEX_SPADE, INDEX_HEART, INDEX_DIAMOND, INDEX_CLUB,
+  INDEX_SPADE, INDEX_HEART, INDEX_DIAMOND, INDEX_CLUB,
+  INDEX_SPADE, INDEX_HEART, INDEX_DIAMOND, INDEX_CLUB
 };
 
-uint16_t const flush[DECK_SIZE] = {
+uint_fast16_t const flush[DECK_SIZE] = {
   ACE_FLUSH,   ACE_FLUSH,   ACE_FLUSH,   ACE_FLUSH,
   KING_FLUSH,  KING_FLUSH,  KING_FLUSH,  KING_FLUSH,
   QUEEN_FLUSH, QUEEN_FLUSH, QUEEN_FLUSH, QUEEN_FLUSH,
@@ -122,4 +122,67 @@ uint16_t const flush[DECK_SIZE] = {
   TWO_FLUSH,   TWO_FLUSH,   TWO_FLUSH,   TWO_FLUSH
 };
 
+uint_fast16_t const flushes[NUMBER_OF_SUITS][DECK_SIZE] = {
+  {
+    ACE_FLUSH,   0, 0, 0,
+    KING_FLUSH,  0, 0, 0,
+    QUEEN_FLUSH, 0, 0, 0,
+    JACK_FLUSH,  0, 0, 0,
+    TEN_FLUSH,   0, 0, 0,
+    NINE_FLUSH,  0, 0, 0,
+    EIGHT_FLUSH, 0, 0, 0,
+    SEVEN_FLUSH, 0, 0, 0,
+    SIX_FLUSH,   0, 0, 0,
+    FIVE_FLUSH,  0, 0, 0,
+    FOUR_FLUSH,  0, 0, 0,
+    THREE_FLUSH, 0, 0, 0,
+    TWO_FLUSH,   0, 0, 0
+  },
+  {
+    0, ACE_FLUSH,   0, 0,
+    0, KING_FLUSH,  0, 0,
+    0, QUEEN_FLUSH, 0, 0,
+    0, JACK_FLUSH,  0, 0,
+    0, TEN_FLUSH,   0, 0,
+    0, NINE_FLUSH,  0, 0,
+    0, EIGHT_FLUSH, 0, 0,
+    0, SEVEN_FLUSH, 0, 0,
+    0, SIX_FLUSH,   0, 0,
+    0, FIVE_FLUSH,  0, 0,
+    0, FOUR_FLUSH,  0, 0,
+    0, THREE_FLUSH, 0, 0,
+    0, TWO_FLUSH,   0, 0
+  },
+  {
+    0, 0, ACE_FLUSH,   0,
+    0, 0, KING_FLUSH,  0,
+    0, 0, QUEEN_FLUSH, 0,
+    0, 0, JACK_FLUSH,  0,
+    0, 0, TEN_FLUSH,   0,
+    0, 0, NINE_FLUSH,  0,
+    0, 0, EIGHT_FLUSH, 0,
+    0, 0, SEVEN_FLUSH, 0,
+    0, 0, SIX_FLUSH,   0,
+    0, 0, FIVE_FLUSH,  0,
+    0, 0, FOUR_FLUSH,  0,
+    0, 0, THREE_FLUSH, 0,
+    0, 0, TWO_FLUSH,   0
+  },
+  {
+    0, 0, 0, ACE_FLUSH,
+    0, 0, 0, KING_FLUSH,
+    0, 0, 0, QUEEN_FLUSH,
+    0, 0, 0, JACK_FLUSH,
+    0, 0, 0, TEN_FLUSH,
+    0, 0, 0, NINE_FLUSH,
+    0, 0, 0, EIGHT_FLUSH,
+    0, 0, 0, SEVEN_FLUSH,
+    0, 0, 0, SIX_FLUSH,
+    0, 0, 0, FIVE_FLUSH,
+    0, 0, 0, FOUR_FLUSH,
+    0, 0, 0, THREE_FLUSH,
+    0, 0, 0, TWO_FLUSH
+  }
+};
+
 #endif
diff --git a/src/FlushCheck.h b/src/FlushCheck.h
index 7e7e84c..aca0ed6 100644
--- a/src/FlushCheck.h
+++ b/src/FlushCheck.h
@@ -22,27 +22,27 @@
 
 #include <cstdint>
 
-int8_t const flush_check[400] = {
-  0, 0, 0, -2, -2, 1, 1, 1, 0, 0, -2, -2, -2, 1, 1, -1, 0, -2, -2, -2, -2, 1, 
-  -1, -1, -2, -2, -2, -2, -2, -1, -1, -1, -2, -2, -2, -2, -1, -1, -1, -1, 8, 8, 
-  8, -1, -1, -1, -1, -1, 8, 8, -1, -1, -1, -1, -1, -1, 8, 0, 0, -2, -2, -2, 1, 1, 
-  -1, 0, -2, -2, -2, -2, 1, -1, -1, -2, -2, -2, -2, -2, -1, -1, -1, -2, -2, -2, 
-  -2, -1, -1, -1, -1, -2, -2, -2, -1, -1, -1, -1, -1, 8, 8, -1, -1, -1, -1, -1, 
-  -1, 8, -1, -1, -1, -1, -1, -1, -1, -1, 0, -2, -2, -2, -2, 1, -1, -1, -2, -2, 
-  -2, -2, -2, -1, -1, -1, -2, -2, -2, -2, -1, -1, -1, -1, -2, -2, -2, -1, -1, -1, 
-  -1, -1, -2, -2, -1, -1, -1, -1, -1, -1, 8, -1, -1, -1, -1, -1, -1, -1, -1, -1, 
-  -1, -1, -1, -1, -1, -1, -1, -2, -2, -2, -2, -2, -1, -1, -1, -2, -2, -2, -2, -1, 
-  -1, -1, -1, -2, -2, -2, -1, -1, -1, -1, -1, -2, -2, -1, -1, -1, -1, -1, -1, -2, 
-  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 
-  -1, -1, -1, -1, -2, -2, -2, -2, -1, -1, -1, -1, -2, -2, -2, -1, -1, -1, -1, -1, 
-  -2, -2, -1, -1, -1, -1, -1, -1, -2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 
-  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 
-  -1, 57, 57, 57, -1, -1, -1, -1, -1, 57, 57, -1, -1, -1, -1, -1, -1, 57, -1, -1, 
-  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 
-  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 57, 57, 
-  -1, -1, -1, -1, -1, -1, 57, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 
-  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 
-  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 57
+int_fast8_t const flush_check[400] = {
+  0, 0, 0, -2, -2, 1, 1, 1, 0, 0, -2, -2, -2, 1, 1, -1, 0, -2, -2, -2, -2, 1,
+  -1, -1, -2, -2, -2, -2, -2, -1, -1, -1, -2, -2, -2, -2, -1, -1, -1, -1, 2, 2,
+  2, -1, -1, -1, -1, -1, 2, 2, -1, -1, -1, -1, -1, -1, 2, 0, 0, -2, -2, -2, 1, 1,
+  -1, 0, -2, -2, -2, -2, 1, -1, -1, -2, -2, -2, -2, -2, -1, -1, -1, -2, -2, -2,
+  -2, -1, -1, -1, -1, -2, -2, -2, -1, -1, -1, -1, -1, 2, 2, -1, -1, -1, -1, -1,
+  -1, 2, -1, -1, -1, -1, -1, -1, -1, -1, 0, -2, -2, -2, -2, 1, -1, -1, -2, -2,
+  -2, -2, -2, -1, -1, -1, -2, -2, -2, -2, -1, -1, -1, -1, -2, -2, -2, -1, -1, -1,
+  -1, -1, -2, -2, -1, -1, -1, -1, -1, -1, 2, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -2, -2, -2, -2, -2, -1, -1, -1, -2, -2, -2, -2, -1,
+  -1, -1, -1, -2, -2, -2, -1, -1, -1, -1, -1, -2, -2, -1, -1, -1, -1, -1, -1, -2,
+  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -2, -2, -2, -2, -1, -1, -1, -1, -2, -2, -2, -1, -1, -1, -1, -1,
+  -2, -2, -1, -1, -1, -1, -1, -1, -2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, 3, 3, 3, -1, -1, -1, -1, -1, 3, 3, -1, -1, -1, -1, -1, -1, 3, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 3, 3,
+  -1, -1, -1, -1, -1, -1, 3, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 3
 };
 
 #endif // SKPOKEREVAL_FLUSHCHECK_H
diff --git a/src/Profiler.cpp b/src/Profiler.cpp
index 79c561b..7d48464 100644
--- a/src/Profiler.cpp
+++ b/src/Profiler.cpp
@@ -37,7 +37,7 @@ class Profiler {
   static clock_t Profile(unsigned const count) {
     std::default_random_engine gen;
     std::uniform_int_distribution<int> dist(0, 51);
-    int const length = 7*count;
+    int const length = 28*count;
     unsigned * const buffer = (unsigned *) malloc(length * sizeof(unsigned));
     for (int i = 0; i < length; i += 7) {
       int j = 0;
@@ -54,11 +54,23 @@ class Profiler {
       }
     }
     std::clock_t const start = std::clock();
-    for (int i = 0; i < length; i += 7) {
+    for (int i = 0; i < length; i += 28) {
+      doNotOptimiseAway(
+        SevenEval::GetRank(buffer[i+21], buffer[i+22], buffer[i+23],
+          buffer[i+24], buffer[i+25], buffer[i+26], buffer[i+27])
+      );
       doNotOptimiseAway(
         SevenEval::GetRank(buffer[i], buffer[i+1], buffer[i+2],
           buffer[i+3], buffer[i+4], buffer[i+5], buffer[i+6])
       );
+      doNotOptimiseAway(
+        SevenEval::GetRank(buffer[i+7], buffer[i+8], buffer[i+9],
+          buffer[i+10], buffer[i+11], buffer[i+12], buffer[i+13])
+      );
+      doNotOptimiseAway(
+        SevenEval::GetRank(buffer[i+14], buffer[i+15], buffer[i+16],
+          buffer[i+17], buffer[i+18], buffer[i+19], buffer[i+20])
+      );
     }
     std::clock_t const end = std::clock();
     delete buffer;
@@ -66,12 +78,19 @@ class Profiler {
   }
 };
 
+float clocksToMilliseconds(clock_t c) {
+  return 1000.0f * c / CLOCKS_PER_SEC;
+}
+
 int main() {
   clock_t fastest = std::numeric_limits<clock_t>::max();
   for (int i = 0; i < 20; ++i) {
-    fastest = std::min(fastest, Profiler::Profile(50000000));
+    clock_t const profile = Profiler::Profile(12500000);
+    fastest = std::min(fastest, profile);
+    std::cout << i << ": " << clocksToMilliseconds(profile) << "ms"
+      << std::endl;
   }
-  std::cout << 1000.0f * fastest / CLOCKS_PER_SEC << " ms" << std::endl;
+  std::cout << "Result: " << clocksToMilliseconds(fastest) << "ms" << std::endl;
 }
 
 #endif
diff --git a/src/SevenEval.h b/src/SevenEval.h
index c0ab4c4..e867f43 100644
--- a/src/SevenEval.h
+++ b/src/SevenEval.h
@@ -39,23 +39,16 @@ class SevenEval {
     uint_fast32_t key = card[i] + card[j] + card[k] + card[l] + card[m] +
       card[n] + card[p];
     // Tear off the flush check strip.
-    int_fast8_t const flush_suit = flush_check[key & SUIT_BIT_MASK];
-    if (NOT_A_FLUSH == flush_suit) {
+    int_fast8_t const suit = flush_check[key & SUIT_BIT_MASK];
+    if (NOT_A_FLUSH == suit) {
       // Tear off the non-flush key strip, and look up the rank.
       key >>= NON_FLUSH_BIT_SHIFT;
       return rank_hash[offsets[key >> RANK_OFFSET_SHIFT] +
         (key & RANK_HASH_MOD)];
     }
     // Generate a flush key, and look up the rank.
-    int flush_key = 0;
-    if (suit[i] == flush_suit) flush_key  = flush[i];
-    if (suit[j] == flush_suit) flush_key += flush[j];
-    if (suit[k] == flush_suit) flush_key += flush[k];
-    if (suit[l] == flush_suit) flush_key += flush[l];
-    if (suit[m] == flush_suit) flush_key += flush[m];
-    if (suit[n] == flush_suit) flush_key += flush[n];
-    if (suit[p] == flush_suit) flush_key += flush[p];
-    return flush_ranks[flush_key];
+    uint_fast16_t const * const s = flushes[suit];
+    return flush_ranks[s[i] + s[j] + s[k] + s[l] + s[m] + s[n] + s[p]];
   }
 };