Add benchmarks for Map4 to HashMap and Set4 to HashSet transitions

1 files changed, 29 insertions, 0 deletions

diff --git a/test/benchmarks/src/main/scala/scala/collection/immutable/SetBenchmark.scala b/test/benchmarks/src/main/scala/scala/collection/immutable/SetBenchmark.scala
new file mode 100644
index 0000000000..9330626691
--- /dev/null
+++ b/test/benchmarks/src/main/scala/scala/collection/immutable/SetBenchmark.scala
@@ -0,0 +1,29 @@
+package scala.collection.immutable
+
+import java.util.concurrent.TimeUnit
+
+import org.openjdk.jmh.annotations._
+import org.openjdk.jmh.infra._
+
+@BenchmarkMode(Array(Mode.AverageTime))
+@Fork(2)
+@Threads(1)
+@Warmup(iterations = 10)
+@Measurement(iterations = 10)
+@OutputTimeUnit(TimeUnit.NANOSECONDS)
+@State(Scope.Benchmark)
+class SetBenchmark {
+
+  var base: Set[String] = _
+
+
+  @Setup(Level.Trial) def initKeys(): Unit = {
+    base = Set("a", "b", "c", "d")
+  }
+  
+  // immutable map is implemented as EmptySet -> Set1 -> Set2 -> Set3 -> Set4 -> HashSet
+  // add an extra entry to Set4 causes a lot of work, benchmark the transition
+  @Benchmark def set4AddElement(bh: Blackhole): Unit = {
+    bh.consume(base + "e")
+  }
+}