Add mergeSort benchmark to tupleOps.scala

Author: Antoine Brunner

bench-run/src/main/scala/dotty/tools/benchmarks/tuples/TupleOps.scala

@@ -1,11 +1,13 @@
 package dotty.tools.benchmarks.tuples
 
 import org.openjdk.jmh.annotations._
+import scala.util.Random
 
 @State(Scope.Thread)
 class TupleOps {
   var tuple1: Tuple = _
   var tuple2: Tuple = _
+  var tuple3: Tuple = _
 
   @Setup
   def setup(): Unit = {
@@ -16,6 +18,8 @@ class TupleOps {
     tuple2 = ()
     for (i <- 1 until 10)
       tuple2 = s"elem$i" *: tuple2
+
+    tuple3 = Tuple.fromArray(Random.shuffle(1 to 15).toArray)
   }
 
   def tupleFlatMap(tuple: Tuple, f: [A] => A => Tuple): Tuple = {
@@ -34,6 +38,22 @@ class TupleOps {
     tailRecReverse(tuple, ())
   }
 
+  def tupleMerge(tuple1: Tuple, tuple2: Tuple): Tuple = (tuple1, tuple2) match {
+    case (_, ()) => tuple1
+    case ((), _) => tuple2
+    case (x *: xs, y *: ys) =>
+      if (x.asInstanceOf[Int] <= y.asInstanceOf[Int]) x *: tupleMerge(xs, tuple2)
+      else y *: tupleMerge(tuple1, ys)
+  }
+
+  def tupleMergeSort(tuple: Tuple): Tuple =
+    if (tuple.size <= 1) tuple
+    else {
+      val (tuple1, tuple2) = tuple.splitAt(tuple.size / 2)
+      val (sorted1, sorted2) = (tupleMergeSort(tuple1), tupleMergeSort(tuple2))
+      tupleMerge(sorted1, sorted2)
+    }
+
   @Benchmark
   def reverse(): Tuple = {
     tupleReverse(tuple1)
@@ -43,4 +63,9 @@ class TupleOps {
   def flatMap(): Tuple = {
     tupleFlatMap(tuple2, [A] => (x: A) => (x, x))
   }
+
+  @Benchmark
+  def mergeSort(): Tuple = {
+    tupleMergeSort(tuple3)
+  }
 }