From a1031d2dc105fa7e8d9ba0e2e0f12890181a55f7 Mon Sep 17 00:00:00 2001
From: Chris Laprun <claprun@redhat.com>
Date: Wed, 10 Jul 2024 22:13:01 +0200
Subject: [PATCH] feat: added HdrHistogram-backed MeasureStore

---
 measure/pom.xml                               |  5 ++
 .../DescriptiveStatisticsMeasureStore.java    | 26 ++++---
 .../measure/HdrHistogramMeasureStore.java     | 69 +++++++++++++++++++
 3 files changed, 91 insertions(+), 9 deletions(-)
 create mode 100644 measure/src/main/java/net/laprun/sustainability/power/measure/HdrHistogramMeasureStore.java

diff --git a/measure/pom.xml b/measure/pom.xml
index dff0b6e..446166e 100644
--- a/measure/pom.xml
+++ b/measure/pom.xml
@@ -23,6 +23,11 @@
       <artifactId>commons-math3</artifactId>
       <version>3.6.1</version>
     </dependency>
+    <dependency>
+      <groupId>org.hdrhistogram</groupId>
+      <artifactId>HdrHistogram</artifactId>
+      <version>2.2.2</version>
+    </dependency>
   </dependencies>
 
   <build>
diff --git a/measure/src/main/java/net/laprun/sustainability/power/measure/DescriptiveStatisticsMeasureStore.java b/measure/src/main/java/net/laprun/sustainability/power/measure/DescriptiveStatisticsMeasureStore.java
index a416dfe..0e08df8 100644
--- a/measure/src/main/java/net/laprun/sustainability/power/measure/DescriptiveStatisticsMeasureStore.java
+++ b/measure/src/main/java/net/laprun/sustainability/power/measure/DescriptiveStatisticsMeasureStore.java
@@ -3,12 +3,12 @@
 import org.apache.commons.math3.stat.descriptive.DescriptiveStatistics;
 
 class DescriptiveStatisticsMeasureStore implements MeasureStore {
+    private final int totalIndex;
     private final DescriptiveStatistics[] measures;
-    private final DescriptiveStatistics total;
 
     public DescriptiveStatisticsMeasureStore(int componentsNumber, int initialWindow) {
-        total = new DescriptiveStatistics(initialWindow);
-        this.measures = new DescriptiveStatistics[componentsNumber];
+        this.measures = new DescriptiveStatistics[componentsNumber + 1];
+        totalIndex = componentsNumber;
         for (int i = 0; i < measures.length; i++) {
             measures[i] = new DescriptiveStatistics(initialWindow);
         }
@@ -16,31 +16,39 @@ public DescriptiveStatisticsMeasureStore(int componentsNumber, int initialWindow
 
     @Override
     public void recordComponentValue(int component, double value) {
-        measures[component].addValue(value);
+        getMeasure(component).addValue(value);
+    }
+
+    private DescriptiveStatistics getMeasure(int component) {
+        return measures[component];
+    }
+
+    private DescriptiveStatistics getTotalMeasure() {
+        return getMeasure(totalIndex);
     }
 
     @Override
     public void recordTotal(double value) {
-        total.addValue(value);
+        getTotalMeasure().addValue(value);
     }
 
     @Override
     public double getMeasuredTotal() {
-        return total.getSum();
+        return getTotalMeasure().getSum();
     }
 
     @Override
     public double getComponentStandardDeviation(int component) {
-        return measures[component].getStandardDeviation();
+        return getMeasure(component).getStandardDeviation();
     }
 
     @Override
     public double getTotalStandardDeviation() {
-        return total.getStandardDeviation();
+        return getTotalMeasure().getStandardDeviation();
     }
 
     @Override
     public double[] getComponentRawValues(int component) {
-        return measures[component].getValues();
+        return getMeasure(component).getValues();
     }
 }
diff --git a/measure/src/main/java/net/laprun/sustainability/power/measure/HdrHistogramMeasureStore.java b/measure/src/main/java/net/laprun/sustainability/power/measure/HdrHistogramMeasureStore.java
new file mode 100644
index 0000000..1d5c566
--- /dev/null
+++ b/measure/src/main/java/net/laprun/sustainability/power/measure/HdrHistogramMeasureStore.java
@@ -0,0 +1,69 @@
+package net.laprun.sustainability.power.measure;
+
+import org.HdrHistogram.HistogramIterationValue;
+import org.HdrHistogram.IntCountsHistogram;
+
+public class HdrHistogramMeasureStore implements MeasureStore {
+    private static final int HIGHEST_TRACKABLE_VALUE = 1_000_000;
+    private static final int NUMBER_OF_SIGNIFICANT_VALUE_DIGITS = 4;
+    private static final int CONVERSION_FACTOR = 1000;
+    private final IntCountsHistogram[] measures;
+    private final int totalIndex;
+    private double accumulatedTotal;
+
+    public HdrHistogramMeasureStore(int componentsNumber, int initialWindow) {
+        totalIndex = componentsNumber;
+        measures = new IntCountsHistogram[componentsNumber + 1];
+        for (int i = 0; i < measures.length; i++) {
+            measures[i] = new IntCountsHistogram(HIGHEST_TRACKABLE_VALUE,
+                    NUMBER_OF_SIGNIFICANT_VALUE_DIGITS);
+        }
+    }
+
+    private IntCountsHistogram getMeasure(int component) {
+        return measures[component];
+    }
+
+    private IntCountsHistogram getTotalMeasure() {
+        return getMeasure(totalIndex);
+    }
+
+    @Override
+    public void recordComponentValue(int component, double value) {
+        getMeasure(component).recordValue((long) (CONVERSION_FACTOR * value));
+    }
+
+    @Override
+    public void recordTotal(double value) {
+        getTotalMeasure().recordValue((long) (CONVERSION_FACTOR * value));
+        accumulatedTotal += value;
+    }
+
+    @Override
+    public double getMeasuredTotal() {
+        return accumulatedTotal;
+    }
+
+    @Override
+    public double getComponentStandardDeviation(int component) {
+        return getMeasure(component).getStdDeviation() / CONVERSION_FACTOR;
+    }
+
+    @Override
+    public double getTotalStandardDeviation() {
+        // not unbiased so tests will fail
+        return getTotalMeasure().getStdDeviation();
+    }
+
+    @Override
+    public double[] getComponentRawValues(int component) {
+        final var measure = getMeasure(component);
+        final var totalCount = measure.getTotalCount();
+        final var result = new double[(int) totalCount];
+        int index = 0;
+        for (HistogramIterationValue value : measure.recordedValues()) {
+            result[index++] = (double) value.getValueIteratedTo() / CONVERSION_FACTOR;
+        }
+        return result;
+    }
+}