Some improvements for dotc.Bench

Author: odersky

compiler/src/dotty/tools/dotc/Bench.scala

@@ -10,38 +10,54 @@ import scala.annotation.internal.sharable
  *  number of compilers and run each (sequentially) a given number of times
  *  on the same sources.
  */
-object Bench extends Driver {
+object Bench extends Driver:
 
   @sharable private var numRuns = 1
 
   private def ntimes(n: Int)(op: => Reporter): Reporter =
     (0 until n).foldLeft(emptyReporter)((_, _) => op)
 
+  @sharable private var times: Array[Int] = _
+
   override def doCompile(compiler: Compiler, fileNames: List[String])(using Context): Reporter =
-    ntimes(numRuns) {
+    times = new Array[Int](numRuns)
+    var reporter: Reporter = emptyReporter
+    for i <- 0 until numRuns do
       val start = System.nanoTime()
-      val r = super.doCompile(compiler, fileNames)
-      println(s"time elapsed: ${(System.nanoTime - start) / 1000000}ms")
-      if (ctx.settings.Xprompt.value) {
+      reporter = super.doCompile(compiler, fileNames)
+      times(i) = ((System.nanoTime - start) / 1000000).toInt
+      println(s"time elapsed: ${times(i)}ms")
+      if ctx.settings.Xprompt.value then
         print("hit <return> to continue >")
         System.in.read()
         println()
-      }
-      r
-    }
+    reporter
 
   def extractNumArg(args: Array[String], name: String, default: Int = 1): (Int, Array[String]) = {
     val pos = args indexOf name
     if (pos < 0) (default, args)
     else (args(pos + 1).toInt, (args take pos) ++ (args drop (pos + 2)))
   }
 
-  override def process(args: Array[String], rootCtx: Context): Reporter = {
+  def reportTimes() =
+    val best = times.sorted
+    val measured = numRuns / 3
+    val avgBest = best.take(measured).sum / measured
+    val avgLast = times.reverse.take(measured).sum / measured
+    println(s"best out of $numRuns runs: ${best(0)}")
+    println(s"average out of best $measured: $avgBest")
+    println(s"average out of last $measured: $avgLast")
+
+  override def process(args: Array[String], rootCtx: Context): Reporter =
     val (numCompilers, args1) = extractNumArg(args, "#compilers")
     val (numRuns, args2) = extractNumArg(args1, "#runs")
     this.numRuns = numRuns
-    ntimes(numCompilers)(super.process(args2, rootCtx))
-  }
-}
+    var reporter: Reporter = emptyReporter
+    for i <- 0 until numCompilers do
+      reporter = super.process(args2, rootCtx)
+    reportTimes()
+    reporter
+
+end Bench
 
 

compiler/src/dotty/tools/dotc/config/Config.scala

@@ -50,7 +50,7 @@ object Config {
   final val checkBackendNames = false
 
   /** Check that re-used type comparers are in their initialization state */
-  final val checkTypeComparerReset = true
+  final val checkTypeComparerReset = false
 
   /** Type comparer will fail with an assert if the upper bound
    *  of a constrained parameter becomes Nothing. This should be turned