address Joseph's comments

Author: mengxr

mllib/src/main/scala/org/apache/spark/ml/util/stopwatches.scala

@@ -50,7 +50,7 @@ private[spark] abstract class Stopwatch extends Serializable {
    */
   def stop(): Long = {
     assume(running, "stop() called but the stopwatch is not running.")
-    val duration = now  - startTime
+    val duration = now - startTime
     add(duration)
     running = false
     duration
@@ -100,7 +100,7 @@ private[spark] class DistributedStopwatch(
     sc: SparkContext,
     override val name: String) extends Stopwatch {
 
-  val elapsedTime: Accumulator[Long] = sc.accumulator(0L, s"DistributedStopwatch($name)")
+  private val elapsedTime: Accumulator[Long] = sc.accumulator(0L, s"DistributedStopwatch($name)")
 
   override def elapsed(): Long = elapsedTime.value
 
@@ -144,9 +144,8 @@ private[spark] class MultiStopwatch(@transient private val sc: SparkContext) ext
   def apply(name: String): Stopwatch = stopwatches(name)
 
   override def toString: String = {
-    "MultiStopwatch" +
-      stopwatches.values.toArray.sortBy(_.name)
-        .map(c => s"  ${c.name} -> ${c.elapsed()}ms")
-        .mkString("(\n", ",\n", "\n)")
+    stopwatches.values.toArray.sortBy(_.name)
+      .map(c => s"  ${c.name}: ${c.elapsed()}ms")
+      .mkString("{\n", ",\n", "\n}")
   }
 }

mllib/src/test/scala/org/apache/spark/ml/util/StopwatchSuite.scala

@@ -34,13 +34,13 @@ class StopwatchSuite extends SparkFunSuite with MLlibTestSparkContext {
     val duration = sw.stop()
     assert(duration >= 50 && duration < 100) // using a loose upper bound
     val elapsed = sw.elapsed()
-    assert(elapsed >= 50 && elapsed < 100)
+    assert(elapsed === duration)
     sw.start()
     Thread.sleep(50)
     val duration2 = sw.stop()
     assert(duration2 >= 50 && duration2 < 100)
     val elapsed2 = sw.elapsed()
-    assert(elapsed2 >= 100 && elapsed2 < 200)
+    assert(elapsed2 == duration + duration2)
     sw.start()
     assert(sw.isRunning)
     intercept[AssertionError] {
@@ -80,7 +80,7 @@ class StopwatchSuite extends SparkFunSuite with MLlibTestSparkContext {
     intercept[NoSuchElementException] {
       sw("some")
     }
-    assert(sw.toString === "MultiStopwatch(\n  local -> 0ms,\n  spark -> 0ms\n)")
+    assert(sw.toString === "{\n  local: 0ms,\n  spark: 0ms\n}")
     sw("local").start()
     sw("spark").start()
     Thread.sleep(50)
@@ -92,7 +92,7 @@ class StopwatchSuite extends SparkFunSuite with MLlibTestSparkContext {
     assert(localElapsed >= 50 && localElapsed < 100)
     assert(sparkElapsed >= 100 && sparkElapsed < 200)
     assert(sw.toString ===
-      s"MultiStopwatch(\n  local -> ${localElapsed}ms,\n  spark -> ${sparkElapsed}ms\n)")
+      s"{\n  local: ${localElapsed}ms,\n  spark: ${sparkElapsed}ms\n}")
     val rdd = sc.parallelize(0 until 4, 4)
     rdd.foreach { i =>
       sw("local").start()