From f3959810cb1097cd7c119595060bcff6e02fd8b3 Mon Sep 17 00:00:00 2001
From: John Wellbelove <github@wellbelove.co.uk>
Date: Sun, 7 Jul 2019 16:35:34 +0100
Subject: [PATCH] Optimisation of floating point specialisations of
 etl::cumulative_moving_average.

---
 include/etl/cumulative_moving_average.h | 31 +++++++++----------------
 include/etl/version.h                   |  2 +-
 support/Release notes.txt               |  4 ++++
 3 files changed, 16 insertions(+), 21 deletions(-)

diff --git a/include/etl/cumulative_moving_average.h b/include/etl/cumulative_moving_average.h
index 95e476cb..df90d3d2 100644
--- a/include/etl/cumulative_moving_average.h
+++ b/include/etl/cumulative_moving_average.h
@@ -202,9 +202,8 @@ namespace etl
     /// \param initial_value The initial value for the average.
     //*************************************************************************
     cumulative_moving_average(const T initial_value)
-      : samples(T(SAMPLE_SIZE_)),
-        samples_plus_1(T(SAMPLE_SIZE_ + 1U)),
-        average(initial_value)
+      : reciprocal_samples_plus_1(T(1.0) / T(SAMPLE_SIZE_ + 1U))
+      , average(initial_value)
     {
     }
 
@@ -223,9 +222,7 @@ namespace etl
     //*************************************************************************
     void add(const T new_value)
     {
-      average *= samples;
-      average += new_value;
-      average /= samples_plus_1;
+      average += (new_value - average) * reciprocal_samples_plus_1;
     }
 
     //*************************************************************************
@@ -239,9 +236,8 @@ namespace etl
 
   private:
 
-    const T samples;        ///< The sample size to average over.
-    const T samples_plus_1; ///< One greater than the sample size.
-    T       average;            ///< The current cumulative average.
+    const T reciprocal_samples_plus_1; ///< Reciprocal of one greater than the sample size.
+    T       average;                   ///< The current cumulative average.
   };
 
   //***************************************************************************
@@ -260,9 +256,8 @@ namespace etl
     /// \param initial_value The initial value for the average.
     //*************************************************************************
     cumulative_moving_average(const T initial_value, const size_t sample_size)
-      : samples(T(sample_size)),
-        samples_plus_1(T(sample_size + 1U)),
-        average(initial_value)
+      : reciprocal_samples_plus_1(T(1.0) / T(sample_size + 1U))
+      , average(initial_value)
     {
     }
 
@@ -281,8 +276,7 @@ namespace etl
     //*************************************************************************
     void set_sample_size(const size_t sample_size)
     {
-      samples = T(sample_size);
-      samples_plus_1 = samples + T(1);
+      reciprocal_samples_plus_1 = T(1.0) / (T(sample_size) + T(1));
     }
 
     //*************************************************************************
@@ -291,9 +285,7 @@ namespace etl
     //*************************************************************************
     void add(const T new_value)
     {
-      average *= samples;
-      average += new_value;
-      average /= samples_plus_1;
+      average += (new_value - average) * reciprocal_samples_plus_1;
     }
 
     //*************************************************************************
@@ -307,9 +299,8 @@ namespace etl
 
   private:
 
-    T samples;        ///< The sample size to average over.
-    T samples_plus_1; ///< One greater than the sample size.
-    T average;            ///< The current cumulative average.
+    T reciprocal_samples_plus_1; ///< Reciprocal of one greater than the sample size.
+    T average;                   ///< The current cumulative average.
   };
 }
 
diff --git a/include/etl/version.h b/include/etl/version.h
index 92a421e8..3edc3888 100644
--- a/include/etl/version.h
+++ b/include/etl/version.h
@@ -39,7 +39,7 @@ SOFTWARE.
 
 #define ETL_VERSION_MAJOR 14
 #define ETL_VERSION_MINOR 28
-#define ETL_VERSION_PATCH  0
+#define ETL_VERSION_PATCH  1
 
 #define ETL_VERSION       ETL_STRINGIFY(ETL_VERSION_MAJOR) ETL_STRINGIFY(ETL_VERSION_MINOR) ETL_STRINGIFY(ETL_VERSION_PATCH)
 #define ETL_VERSION_W     ETL_WIDE_STRING(ETL_CONCAT(ETL_CONCAT(ETL_VERSION_MAJOR, ETL_VERSION_MINOR), ETL_VERSION_PATCH))
diff --git a/support/Release notes.txt b/support/Release notes.txt
index 671c522a..1db05040 100644
--- a/support/Release notes.txt	
+++ b/support/Release notes.txt	
@@ -1,3 +1,7 @@
+===============================================================================
+14.28.1
+Optimisation of floating point specialisations of etl::cumulative_moving_average.
+
 ===============================================================================
 14.28.0
 Added runtime sample size specialisations to etl::cumulative_moving_average.