Setting up benchmarks and perf utilities

test/perf/input/async_benchmark.dart

+// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/**
+ * Defines an asynchronous benchmark, where each iteration completes
+ * asynchronously.
+ */
+// TODO(sigmund): move this to the same repo where BenchmarkBase is.
+library async_benchmark;
+
+/** The superclass from which all benchmarks inherit from. */
+class AsyncBenchmark {
+  /** Benchmark name. */
+  final String name;
+
+  const AsyncBenchmark([this.name]);
+
+  /** The benchmark code, invoked by [warmup] and [exercise]. */
+  Future run() => new Future.immediate(null);
+
+  /** Runs a short version of the benchmark. By default invokes [run] once. */
+  Future warmup() => run();
+
+  /** Exercices the benchmark. By default invokes [run] 10 times. */
+  Future exercise() {
+    int count = 10;
+    Future recurse(val) {
+      if (count-- <= 0) return new Future.immediate(val);
+      return run().chain(recurse);
+    }
+    return recurse(null);
+  }
+
+  /** Not measured setup code executed prior to the benchmark runs. */
+  void setup() { }
+
+  /** Not measures teardown code executed after the benchark runs. */
+  void teardown() { }
+
+  /**
+   * Measures the score for this benchmark by executing it repeately until
+   * time minimum has been reached. The result is iterations per sec.
+   */
+  static Future<double> measureFor(AsyncFunction f, int timeMinimum) {
+    int iter = 0;
+    var watch = new Stopwatch();
+    watch.start();
+    Future recurse(val) {
+      int elapsed = watch.elapsedMilliseconds;
+      if (elapsed < timeMinimum || iter < 32) {
+        iter++;
+        return f().chain(recurse);
+      }
+      return new Future.immediate((1000.0 * elapsed) / iter);
+    }
+    return recurse(null);
+  }
+
+  /** Measures and returns the score for the benchmark (bigger is better). */
+  Future<double> measure() {
+    setup();
+    // Warmup for at least 1000ms. Discard result.
+    return measureFor(warmup, 1000).chain((_) {
+      // Run the benchmark for at least 1000ms.
+      return measureFor(exercise, 2000).transform((result) {
+        teardown();
+        return result;
+      });
+    });
+  }
+}
+
+typedef Future AsyncFunction();