Merge pull request #3544 from ControlSystemStudio/CSSTUDIO-3420

CSSTUDIO-3420 Performance improvements to the Waterfall Plot widget

Author: abrahamwolk

app/display/waterfallplot/src/main/java/org/phoebus/applications/waterfallplotwidget/WaterfallPlotController.java

@@ -17,13 +17,12 @@
 
 import java.time.Duration;
 import java.time.Instant;
+import java.util.ArrayList;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Optional;
-import java.util.SortedMap;
-import java.util.TreeMap;
+import java.util.concurrent.ConcurrentSkipListMap;
 import java.util.concurrent.atomic.AtomicBoolean;
-import java.util.concurrent.atomic.AtomicReference;
 
 public class WaterfallPlotController {
 
@@ -309,7 +308,7 @@ public synchronized void redraw(WaterfallPlotRuntime.PVData pvData) {
         previousT2[0] = Optional.of(t2);
 
         LinkedList<Double> timeValuesLinkedList = new LinkedList<>();
-        LinkedList<LinkedList<Double>> zValuesLinkedList = new LinkedList<>();
+        LinkedList<ArrayList<Double>> zValuesLinkedList = new LinkedList<>();
         int waveformLength = 1;
 
         double minFromPV = Double.NaN;
@@ -320,21 +319,24 @@ public synchronized void redraw(WaterfallPlotRuntime.PVData pvData) {
             minFromPV = waveformPVData.minFromPV().get();
             maxFromPV = waveformPVData.maxFromPV().get();
 
-            TreeMap<Instant, LinkedList<Double>> instantToWaveform = waveformPVData.instantToValue().get();
+            ConcurrentSkipListMap<Instant, ArrayList<Double>> instantToWaveform = waveformPVData.instantToValue();
+            Instant startKey = instantToWaveform.ceilingKey(Instant.MIN);
             for (Instant t = t1.plus(stepsize); t.compareTo(t2) <= 0; t = t.plus(stepsize)) {
                 timeValuesLinkedList.add(((double) t.toEpochMilli()) / 1000.0);
 
-                var instant = instantToWaveform.floorKey(t);
-                if (instant != null) {
-                    LinkedList<Double> waveform = instantToWaveform.get(instant);
+                if (startKey == null || t.isBefore(startKey)) {
+                    zValuesLinkedList.add(null); // null means absence of data for this point in time
+                }
+                else {
+                    var instant = instantToWaveform.floorKey(t);
+
+                    ArrayList<Double> waveform = instantToWaveform.get(instant);
                     waveformLength = Math.max(waveformLength, waveform.size());
                     zValuesLinkedList.add(waveform);
-                } else {
-                    zValuesLinkedList.add(null); // null means absence of data for this point in time
                 }
             }
         } else if (pvData instanceof WaterfallPlotRuntime.ScalarPVsData scalarPVsData) {
-            LinkedList<Pair<String, AtomicReference<TreeMap<Instant, Double>>>> pvNameToInstantToValue = scalarPVsData.pvNameToInstantToValue();
+            ArrayList<Pair<String, ConcurrentSkipListMap<Instant, Double>>> pvNameToInstantToValue = scalarPVsData.pvNameToInstantToValue();
             pvNameToInstantToValue.forEach(pvNameAndInstantToValueAtomicReference -> garbageCollectInstantToValue(pvNameAndInstantToValueAtomicReference.getValue(), t1));
 
             minFromPV = scalarPVsData.minFromPV().get();
@@ -344,12 +346,12 @@ public synchronized void redraw(WaterfallPlotRuntime.PVData pvData) {
 
             for (Instant t = t1.plus(stepsize); t.compareTo(t2) <= 0; t = t.plus(stepsize)) {
                 timeValuesLinkedList.add(((double) t.toEpochMilli()) / 1000.0);
-                LinkedList<Double> zValues = new LinkedList<>();
+                ArrayList<Double> zValues = new ArrayList<>();
 
                 for (var pvNameAndInstantToValue : pvNameToInstantToValue) {
                     String pvName = pvNameAndInstantToValue.getKey();
 
-                    TreeMap<Instant, Double> instantToValue = pvNameAndInstantToValue.getValue().get();
+                    ConcurrentSkipListMap<Instant, Double> instantToValue = pvNameAndInstantToValue.getValue();
 
                     var instant = instantToValue.floorKey(t);
                     if (instant == null) {
@@ -363,7 +365,7 @@ public synchronized void redraw(WaterfallPlotRuntime.PVData pvData) {
 
                 // Append the last value one more time in order to
                 // fix the plotting when there is only 1 scalar PV:
-                var lastValue = zValues.getLast();
+                var lastValue = zValues.get(zValues.size()-1);
                 zValues.add(lastValue);
 
                 zValuesLinkedList.add(zValues);
@@ -392,7 +394,7 @@ public synchronized void redraw(WaterfallPlotRuntime.PVData pvData) {
             }
 
             for (int n = 0; n < zValuesLinkedList.size(); n++) {
-                LinkedList<Double> waveformValues = zValuesLinkedList.get(n);
+                ArrayList<Double> waveformValues = zValuesLinkedList.get(n);
 
                 for (int m = 0; m < waveformLength; m++) {
                     double value;
@@ -431,7 +433,7 @@ public synchronized void redraw(WaterfallPlotRuntime.PVData pvData) {
             }
 
             for (int n = 0; n < zValuesLinkedList.size(); n++) {
-                LinkedList<Double> waveformValues = zValuesLinkedList.get(n);
+                ArrayList<Double> waveformValues = zValuesLinkedList.get(n);
 
                 for (int m = 0; m < waveformLength; m++) {
                     double value;
@@ -479,14 +481,13 @@ else if (zAxisMinMax.equals(WaterfallPlotWidget.ZAxisMinMax.FromPVLimits)) {
         }
     }
 
-    private synchronized static <T> void garbageCollectInstantToValue(AtomicReference<TreeMap<Instant, T>> instantToValueAtomicReference, Instant t1) {
+    private synchronized static <T> void garbageCollectInstantToValue(ConcurrentSkipListMap<Instant, T> instantToWaveform, Instant t1) {
         // Garbage collect old values that are no longer needed:
-        TreeMap<Instant, T> instantToWaveform = instantToValueAtomicReference.get();
         Instant instantOfOldestRelevantKey = instantToWaveform.floorKey(t1);
         if (instantOfOldestRelevantKey != null) {
-            SortedMap<Instant, T> instantToWaveformGarbageCollectedSortedMap = instantToWaveform.subMap(instantOfOldestRelevantKey, Instant.MAX);
-            TreeMap<Instant, T> instantToWaveformGarbageCollected = new TreeMap<>(instantToWaveformGarbageCollectedSortedMap);
-            instantToValueAtomicReference.set(instantToWaveformGarbageCollected);
+            for (var key : instantToWaveform.subMap(Instant.MIN, instantOfOldestRelevantKey).keySet()) {
+                instantToWaveform.remove(key);
+            }
         }
     }