Made experiment return a stream

I /think/ this helps with a memory leak, you can garbage collect the
results of an experiment as soon as you have consumed it, instead of
keeping it in memory. I'm not certain that's very important, though,
cause we don't store that many elements...

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

@@ -6,6 +6,7 @@ import se.lth.cs.papicounters.PAPICounter
 import se.lth.cs.papicounters.PapiBenchmarkAnalyzer
 import se.lth.cs.papicounters.PapiTracerRunner
 import se.lth.cs.timing.OperationTypeTable
+import java.util.stream.Stream
 
 class Experiment(val numberIterations : Int,
                  val benchmark : BCBenchmarkPackage<*>,
@@ -26,7 +27,7 @@ class Experiment(val numberIterations : Int,
         }
     }
 
-    fun getIterations(): List<List<PapiTracerRunner.TraceRecord>> {
+    fun getIterations(): Stream<List<PapiTracerRunner.TraceRecord>> {
         val eventSetBuilder = EventSetBuilder()
         eventSetBuilder.visitFeatureSet(features)
 
@@ -37,29 +38,33 @@ class Experiment(val numberIterations : Int,
             PapiBenchmarkAnalyzer.RunSpec(numberIterations, counters.toList(), evSet, benchmark)
         )
 
-        return iterations
+        return iterations.stream()
     }
 
-    fun run() : List<Result> {
-        if (features.isEmpty()) { return listOf() }
+    private fun runIteration(i : List<PapiTracerRunner.TraceRecord>,
+                     iterationNumber: Int): Result {
+        currentIteration = i
+        currentIterationResults = mutableMapOf()
+        // We aggregate all our features for that
+        // specific iteration!
+        features.accept(this)
+        val values = currentIterationResults.toMap()
+
+        return Result(iterationNumber, benchmark, values)
+    }
+
+    fun run() : Stream<Result> {
+        if (features.isEmpty()) { return Stream.empty() }
 
         val iterations = getIterations()
 
         var iterationNumber = 0
-        val results = mutableListOf<Result>()
-        for (i in iterations) {
-            currentIteration = i
-            currentIterationResults = mutableMapOf()
-            // We aggregate all our features for that
-            // specific iteration!
-            features.accept(this)
-            val values = currentIterationResults.toMap()
-
-            results.add(Result(iterationNumber, benchmark, values))
+
+        return iterations.map {
+            val r = runIteration(it, iterationNumber)
             iterationNumber++
+            r
         }
-
-        return results.toList()
     }
 
     var currentIteration : List<PapiTracerRunner.TraceRecord> = listOf()

core/src/test/kotlin/ExperimentTest.kt

@@ -7,6 +7,7 @@ import se.lth.cs.papicounters.PAPICounter
 import se.lth.cs.papicounters.PapiTracerRunner
 import se.lth.cs.timing.OperationType
 import se.lth.cs.util.*
+import java.util.stream.Collectors
 
 class ExperimentTest {
 
@@ -18,7 +19,7 @@ class ExperimentTest {
 
         val exp = Experiment(10, bench, FeatureSet(), runner)
 
-        val results = exp.run()
+        val results = exp.run().collect(Collectors.toList())
         Assertions.assertTrue(results.isEmpty())
     }
 
@@ -30,7 +31,7 @@ class ExperimentTest {
             runner
         )
 
-        val results = exp.run()
+        val results = exp.run().collect(Collectors.toList())
 
         Assertions.assertEquals(10, results.size)
         Assertions.assertEquals(