Add time/space benchmarks

package.json

@@ -33,10 +33,12 @@
   },
   "devDependencies": {
     "jasmine-node": "1.x.x",
-    "pegjs": "git://github.com/dmajda/pegjs.git"
+    "pegjs": "git://github.com/dmajda/pegjs.git",
+    "memwatch": "~0.2.2"
   },
   "scripts": {
     "test": "jasmine-node spec",
-    "build-parser": "pegjs --allowed-start-rules expression,sheet grammar.pegjs"
+    "build-parser": "pegjs --allowed-start-rules expression,sheet grammar.pegjs",
+    "test-perf": "node --expose-gc perf/index.js"
   }
 }

perf/index.js

@@ -0,0 +1,59 @@
+var assert = require("assert");
+var memwatch = require("memwatch");
+
+var Bindings = require("../bindings");
+
+var SIZE = 10000;
+var TIMES = 10;
+
+var makeRandomArray = function(n) {
+    var res = [];
+    for (var i=0; i<n; i++){
+        res.push(Math.floor(Math.random()*100000));
+    }
+    return res;
+};
+
+var observeArray = {
+    frb: function() {
+        var bound = Bindings.defineBindings({
+            array: makeRandomArray(SIZE)
+        }, {
+            sumOfOdds: {"<-": "array.filter{%2}.sum()"}
+        });
+        var r = bound.sumOfOdds;
+        bound.array.push(11);
+        assert(r+11 === bound.sumOfOdds, "FRB logic failed");
+        Bindings.cancelBindings(bound);
+    },
+
+    naive: function() {
+        var array = makeRandomArray(SIZE);
+        var sumOfOdds = function(){
+            return array.filter(function(x){ return x % 2 == 1; }).reduce(function(a, b){ return a+b; });
+        };
+        var r = sumOfOdds();
+        array.push(11);
+        assert(r+11 === sumOfOdds(), "Naive logic failed");
+    }
+};
+
+var test = function(callback) {
+    global.gc();
+    var start = new Date();
+    var hd = new memwatch.HeapDiff();
+
+    for(var i=0; i<TIMES; i++) callback();
+    global.gc();
+
+    var res = hd.end();
+    res.time = new Date() - start;
+    return res;
+};
+
+var compare = function() {
+    console.log("FRB", JSON.stringify(test(observeArray.frb), null, 4));
+    console.log("Naive", JSON.stringify(test(observeArray.naive), null, 4));
+};
+
+compare();