benchmark: separate JMH benchmarks

app/build.gradle.kts

@@ -6,7 +6,9 @@
 plugins {
     // Apply the application plugin to add support for building a CLI application in Java.
     application
+
     // JMH Gradle Plugin
+    // https://github.com/melix/jmh-gradle-plugin/blob/master/README.adoc#usage
     id("me.champeau.jmh") version "0.7.2"
 }
 
@@ -15,14 +17,17 @@ repositories {
     mavenCentral()
 }
 
+val latestJmhVersion = "1.37"
+
 dependencies {
     // Use JUnit Jupiter for testing.
     testImplementation(libs.junit.jupiter)
 
     testRuntimeOnly("org.junit.platform:junit-platform-launcher")
 
-    // This dependency is used by the application.
-    //implementation(libs.guava)
+    // Required to use the IntelliJ plugin "JMH Java Microbenchmark Harness".
+    // https://stackoverflow.com/a/71286156/6334421
+    jmhAnnotationProcessor("org.openjdk.jmh:jmh-generator-annprocess:$latestJmhVersion")
 }
 
 // Apply a specific Java toolchain to ease working on different environments.
@@ -57,4 +62,21 @@ tasks.named<Test>("test") {
         // HTML reports to view with a webbrowser.
         html.required.set(true)
     }
-}
+}
+
+// https://github.com/melix/jmh-gradle-plugin/blob/master/README.adoc#configuration-options
+jmh {
+    // Use latest JMH version (1.37, https://github.com/openjdk/jmh/tags)
+    // instead of default (1.36, https://github.com/melix/jmh-gradle-plugin/blob/dfdbb0cd3a363e2dbbcaab93bb1be32178f4cae4/src/main/java/me/champeau/jmh/DefaultsConfigurer.java#L24)
+    jmhVersion = latestJmhVersion // Specifies JMH version
+
+    // Force GC (garbage collection) between iterations.
+    //
+    //  Forcing the GC may help to lower the noise in GC-heavy benchmarks, at the expense of jeopardizing GC ergonomics decisions. Use with care.
+    // https://github.com/openjdk/jmh/blob/1be779e0b4af174b67abf8080d1b76dda570d88d/jmh-core/src/main/java/org/openjdk/jmh/runner/options/CommandLineOptions.java#L148-L152
+    forceGC = true
+
+    excludes = listOf(
+        "de.uni_marburg.powersort.benchmark.JmhBase.benchmark",
+    )
+}

app/src/jmh/java/de/uni_marburg/powersort/benchmark/JmhBase.java

@@ -3,6 +3,7 @@ package de.uni_marburg.powersort.benchmark;
 import de.uni_marburg.powersort.data.DataEnum;
 import de.uni_marburg.powersort.data.ObjectSupplier;
 import de.uni_marburg.powersort.sort.SortEnum;
+import de.uni_marburg.powersort.sort.SortImpl;
 import org.openjdk.jmh.annotations.Benchmark;
 import org.openjdk.jmh.annotations.BenchmarkMode;
 import org.openjdk.jmh.annotations.Fork;
@@ -10,7 +11,6 @@ import org.openjdk.jmh.annotations.Level;
 import org.openjdk.jmh.annotations.Measurement;
 import org.openjdk.jmh.annotations.Mode;
 import org.openjdk.jmh.annotations.OutputTimeUnit;
-import org.openjdk.jmh.annotations.Param;
 import org.openjdk.jmh.annotations.Scope;
 import org.openjdk.jmh.annotations.Setup;
 import org.openjdk.jmh.annotations.State;
@@ -36,19 +36,24 @@ import java.util.concurrent.TimeUnit;
  * State objects naturally encapsulate the state on which benchmark is working on.
  */
 @State(Scope.Benchmark)
-public class MainJmh {
-    @Param()
-    private DataEnum dataEnum;
-    @Param()
-    private SortEnum sortEnum;
+public class JmhBase {
+    DataEnum getDataEnum(){
+        return null;
+    }
+    SortEnum getSortEnum(){
+        return null;
+    }
 
     private ObjectSupplier data = null;
-    /* package-protected */ Object[] workingCopy;
+    Object[] workingCopy;
+    SortImpl sortImpl;
 
     // TODO: This is inaccurate. How to create and use separate arrays for each warmup x iteration x sortAlgorithm ?
     @Setup(Level.Invocation)
     public void setup() {
-        if(Filter.isFiltered(dataEnum, sortEnum)) {
+        sortImpl = getSortEnum().getSortImpl();
+
+        if (Filter.isFiltered(getDataEnum(), getSortEnum())) {
             // This combination of DataEnum and SortEnum should be skipped.
             // We can't tell JMH to not run the benchmark at all.
             // Instead, we let it sort an invalid list which results in an exception.
@@ -59,12 +64,12 @@ public class MainJmh {
             return;
         }
 
-        // A new MainJmh object is created for each @Param variation.
+        // A new JmhRunner object is created for each @Param variation.
         // Then, `data` is `null` again.
         if (data == null) {
-            data = dataEnum.getObjectSupplier();
+            data = getDataEnum().getObjectSupplier();
         }
-        // For all warmup and measurement iterations of one @Param variation, the MainJmh object is reused.
+        // For all warmup and measurement iterations of one @Param variation, the JmhRunner object is reused.
         // Thus, we can't just sort `data` directly.
         // Instead, we have to create a copy of it on which the sort algorithm can work.
         // This way, all iterations sort the same input.
@@ -73,6 +78,6 @@ public class MainJmh {
 
     @Benchmark
     public void benchmark() {
-        sortEnum.getSortImpl().sort(workingCopy);
+        sortImpl.sort(workingCopy);
     }
 }

app/src/jmh/java/de/uni_marburg/powersort/benchmark/JmhCompetition.java

@@ -0,0 +1,30 @@
+package de.uni_marburg.powersort.benchmark;
+
+import de.uni_marburg.powersort.data.DataEnum;
+import de.uni_marburg.powersort.sort.SortEnum;
+import org.openjdk.jmh.annotations.Param;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.State;
+
+/*
+ * Benchmark state parameters
+ *
+ * Quote from JMH:
+ * State objects naturally encapsulate the state on which benchmark is working on.
+ */
+@State(Scope.Benchmark)
+public class JmhCompetition extends JmhBase {
+    @Param()
+    DataEnum dataEnum;
+    @Param()
+    SortEnum sortEnum;
+
+    @Override
+    DataEnum getDataEnum(){
+        return dataEnum;
+    }
+    @Override
+    SortEnum getSortEnum(){
+        return sortEnum;
+    }
+}

app/src/main/java/de/uni_marburg/powersort/benchmark/SortImpl.java

@@ -1,14 +0,0 @@
-package de.uni_marburg.powersort.benchmark;
-
-public abstract class SortImpl {
-    final String title;
-
-    public SortImpl(String title) {
-        this.title = title;
-    }
-
-    /**
-     * Apply the sort algorithm.
-     */
-    public abstract void sort(Object[] a);
-}

app/src/main/java/de/uni_marburg/powersort/data/ObjectSupplier.java

@@ -3,7 +3,7 @@ package de.uni_marburg.powersort.data;
 import java.util.Arrays;
 
 public abstract class  ObjectSupplier {
-    /* package-protected */ final Object[] readOnly;
+    final Object[] readOnly;
 
     ObjectSupplier(Object[] readOnly) {
         this.readOnly = readOnly;