Optimisation of floating point specialisations of etl::cumulative_mov…

…ing_average.
ETLCPP · Jul 7, 2019 · f395981 · f395981
1 parent 9fbbb5c
commit f395981
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Showing 3 changed files with 16 additions and 21 deletions.
diff --git 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
@@ -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
@@ -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.