Implemented caching of eventSets in EventSetBuilder

Not strictly necessary, since we don't use the generated EventSet in
Experiment. But might be useful later.

core/src/main/kotlin/se/lth/cs/papicounters/EventSetBuilder.kt

@@ -43,25 +43,33 @@ class EventSetBuilder : FeatureVisitor {
         // Do nothing
     }
 
-    private var eventSet : EventSet? = null
-
     override fun visitFeatureSet(featureSet: FeatureSet) {
         for (f in featureSet) {
             f.accept(this)
         }
-
-        val counters = counterSet.map { it.toPAPIConstant()!! }.toIntArray()
-        eventSet = EventSet.create(*counters)
     }
 
     fun getCounterSet() : Set<PAPICounter> {
         return counterSet.toSet()
     }
 
+    companion object {
+        val eventSetCache : MutableMap<Set<PAPICounter>, EventSet> = mutableMapOf()
+    }
+
     fun getEventSet() : EventSet {
-        if (eventSet == null) {
-            throw RuntimeException("EventSet not created! Did you call accept() on the builder?")
+        if (counterSet.isEmpty()) {
+            throw RuntimeException("Counter set is empty! Did you call accept() on the builder?")
+        }
+        return if (eventSetCache.containsKey(counterSet)) {
+            val eventSet = eventSetCache.get(counterSet)!!
+            eventSet.reset()
+            eventSet
+        } else {
+            val counters = counterSet.map { it.toPAPIConstant()!! }.toIntArray()
+            val eventSet = EventSet.create(*counters)
+            eventSetCache.put(counterSet, eventSet!!)
+            eventSet!!
         }
-        return eventSet!!
     }
 }
\ No newline at end of file

core/src/main/kotlin/se/lth/cs/util/Experiment.kt

@@ -29,16 +29,14 @@ class Experiment(val numberIterations : Int,
     fun getIterations(): List<List<PapiTracerRunner.TraceRecord>> {
         val eventSetBuilder = EventSetBuilder()
         eventSetBuilder.visitFeatureSet(features)
-        val counters = eventSetBuilder.getCounterSet()
 
+        val counters = eventSetBuilder.getCounterSet()
         val evSet = eventSetBuilder.getEventSet()
 
         val iterations = papiRunner.runIterations(
             PapiBenchmarkAnalyzer.RunSpec(numberIterations, counters.toList(), evSet, benchmark)
         )
 
-        evSet.destroy()
-
         return iterations
     }