Rewriting weighted random

IRONKLADD · May 5, 2015 · 164412b · 164412b
1 parent fa916cd
commit 164412b
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Showing 3 changed files with 25 additions and 19 deletions.
diff --git a/src/core/Configuration.js b/src/core/Configuration.js
@@ -9,24 +9,8 @@ function Configuration(width, height, colors, magnitudes, specials, types, turns
 
     this.getRandomShell = function() {
         return new Shell(Util.selectRandom(colors),
-                         weightedMagnitude(),
+                         Util.selectWeightedRandom(magnitudes),
                          Util.selectRandom(types),
                          Util.selectRandom(specials));
     }
-    function weightedMagnitude(){
-        var weights = new Map([]);
-        weights.set(1, .40);
-        weights.set(2, .30);
-        weights.set(3, .15);
-        weights.set(4, .10);
-        weights.set(5, .05);
-        var p = 1 - Math.random();
-        for(var i = 1; i <= 5 ; i++){
-            var current = weights.get(i)
-            p = p - current;
-            if(p <= 0){
-                return i;
-            }
-        }
-    }
 }
diff --git a/src/core/Main.js b/src/core/Main.js
@@ -15,7 +15,7 @@ var app = Cut(function(root, container) {
 
         setViewBox(width, height, 40, root);
 
-        var magnitudes = [0];
+        var magnitudes = [[0, 1.0]];
         var specials = [null];
         var types = [Shariki.NORMALSHELL];
         var config = new Configuration(width, height,
@@ -38,7 +38,11 @@ var app = Cut(function(root, container) {
 
         setViewBox(width, height, 40, root);
 
-        var magnitudes = [1, 2, 3, 4, 5];
+        var magnitudes = [[1, 0.40],
+                          [2, 0.30],
+                          [3, 0.15],
+                          [4, 0.10],
+                          [5, 0.05]];
         var specials = [null];
         var types = [Bombi.NORMALSHELL];
         var config = new Configuration(width, height,

diff --git a/src/core/Util.js b/src/core/Util.js
@@ -58,6 +58,24 @@ Util.selectRandom = function(arr) {
     return arr[Util.randomInt(arr.length)];
 };
 
+/**
+ * Returns a random key from an array of key-value pairs, where the values are
+ * the weights. Assumes that values are stochastic (sum to 1.0).
+ *
+ * @param map {Object[][]} 
+ *
+ * @return {Object}
+ */
+Util.selectWeightedRandom = function(arr) {
+    var p = 1 - Math.random();
+    for(var i = 0; i < arr.length; ++i) {
+        p -= arr[i][1];
+        if(p <= 0) {
+            return arr[i][0];
+        }
+    }
+}
+
 /**
  * Returns a coordinate object.
  *