adding benchmark script

.gitignore

@@ -1,2 +1,3 @@
 node_modules
 dist
+perf/versions

package.json

@@ -19,8 +19,10 @@
   },
   "license": "MIT",
   "devDependencies": {
+    "benchmark": "~1.0.0",
     "jshint": "~2.7.0",
     "lodash": ">=2.4.1",
+    "mkdirp": "~0.5.1",
     "nodeunit": ">0.0.0",
     "uglify-js": "1.2.x"
   },

perf/benchmark.js

@@ -0,0 +1,108 @@
+#!/usr/bin/env node
+
+var Benchmark = require("benchmark");
+var benchOptions = {defer: true, minSamples: 7};
+var exec = require("child_process").exec;
+var fs = require("fs");
+var mkdirp = require("mkdirp");
+var async = require("../");
+var suiteConfigs = require("./suites");
+
+var version1 = process.argv[2] || require("../package.json").version;
+var version2 = process.argv[3] || "current";
+var versionNames = [version1, version2];
+var versions;
+var wins = [0, 0];
+
+console.log("Comparing " + version1 + " with " + version2);
+console.log("--------------------------------------");
+
+
+async.eachSeries(versionNames, cloneVersion, function (err) {
+  versions = versionNames.map(requireVersion);
+
+  var suites = suiteConfigs.map(createSuite);
+
+  async.eachSeries(suites, runSuite, function () {
+    var wins0 = wins[0].length;
+    var wins1 = wins[1].length;
+
+    if (wins0 > wins1) {
+      console.log(versionNames[0] + " faster overall " +
+        "(" + wins0 + " wins vs. " + wins1  +" wins)");
+    } else if (wins1 > wins0) {
+      console.log(versionNames[1] + " faster overall " +
+        "(" + wins1 + " wins vs. " + wins0  +" wins)");
+    } else {
+      console.log("Both versions are equal");
+    }
+  });
+});
+
+function runSuite(suite, callback) {
+  suite.on("complete", function () {
+    callback();
+  }).run({async: true});
+}
+
+function createSuite(suiteConfig) {
+  var suite = new Benchmark.Suite();
+
+  function addBench(version, versionName) {
+    var title = suiteConfig.name + " " + versionName;
+    suite.add(title, function (deferred) {
+      suiteConfig.fn(versions[0], deferred);
+    }, benchOptions);
+  }
+
+  addBench(versions[0], versionNames[0]);
+  addBench(versions[1], versionNames[1]);
+
+  return suite.on('cycle', function(event) {
+    console.log(event.target + "");
+  })
+  .on('complete', function() {
+    var fastest = this.filter('fastest');
+    if (fastest.length === 2) {
+      console.log("Tie");
+    } else {
+      console.log(fastest[0].name + ' is faster');
+      var index = this.indexOf("fastest");
+      wins[index]++;
+    }
+    console.log("--------------------------------------");
+  });
+
+}
+
+function requireVersion(tag) {
+  if (tag === "current") {
+    return async;
+  }
+
+  return require("./versions/" + tag + "/");
+}
+
+function cloneVersion(tag, callback) {
+  if (tag === "current") return callback();
+
+  var versionDir = __dirname + "/versions/" + tag;
+  mkdirp.sync(versionDir);
+  fs.open(versionDir + "/package.json", "r", function (err, handle) {
+    if (!err) {
+      // version has already been cloned
+      fs.close(handle);
+      return callback();
+    }
+
+    var cmd = "git clone --branch " + tag + " ../ " + versionDir;
+
+    exec(cmd, function (err, stdout, stderr) {
+      if (err) {
+        throw err;
+      }
+      callback();
+    });
+
+  });
+}

perf/suites.js

@@ -0,0 +1,40 @@
+module.exports = [
+  {
+    name: "each(10)",
+    fn: function (async, deferred) {
+      async.each(Array(10), function (num, cb) {
+        async.setImmediate(cb);
+      }, done(deferred));
+    }
+  },
+  {
+    name: "each(10000)",
+    fn: function (async, deferred) {
+      async.each(Array(10000), function (num, cb) {
+        async.setImmediate(cb);
+      }, done(deferred));
+    }
+  },
+  {
+    name: "eachSeries(10)",
+    fn: function (async, deferred) {
+      async.eachSeries(Array(10), function (num, cb) {
+        async.setImmediate(cb);
+      }, done(deferred));
+    }
+  },
+  {
+    name: "eachSeries(10000)",
+    fn: function (async, deferred) {
+      async.eachSeries(Array(10000), function (num, cb) {
+        async.setImmediate(cb);
+      }, done(deferred));
+    }
+  }
+];
+
+function done(deferred) {
+  return function () {
+    deferred.resolve();
+  };
+}