Fast PRNG instead of the slow Mersenne Twister

src/random.coffee

@@ -1,149 +1,53 @@
 ###
-This implementation of the Mersenne Twister is a port of the JavaScript
-version by Y. Okada. The JavaScript version was itself a port of a
-C implementation, by Takuji Nishimura and Makoto Matsumoto.
+Fast performance pseudo random number generator.
 
-CoffeeScript port by: Jamis Buck <jamis@jamisbuck.org>
-License: Public domain, baby. Knock yourself out.
+Not the cryptographic-level randomness, but enough for most games.
 
-The original CoffeeScript sources are always available on GitHub:
-http://github.com/jamis/csmazes
+Code from CoffeeScript Cookbook:
+https://coffeescript-cookbook.github.io/chapters/math/generating-predictable-random-numbers
 ###
 
 class Random
-  N:          624
-  M:          397
-  MATRIX_A:   0x9908b0df
-  UPPER_MASK: 0x80000000
-  LOWER_MASK: 0x7fffffff
+  constructor: (@seed) ->
+    @multiplier = 1664525
+    @modulo = 4294967296 # 2**32-1;
+    @offset = 1013904223
+    unless @seed? && 0 <= seed < @modulo
+      @seed = (new Date().valueOf() * new Date().getMilliseconds()) % @modulo
 
-  constructor: (seed) ->
-    @mt = new Array(@N)
-    @setSeed seed
+  # sets new seed value
+  seed: (seed) ->
+    @seed = seed
 
-  # makes the argument into an unsigned integer, if it is not already one
-  unsigned32: (n1) -> if n1 < 0 then (n1 ^ @UPPER_MASK) + @UPPER_MASK else n1
+  getSeed: () ->
+    return @seed
 
-  # emulates underflow of subtracting two 32-bit unsigned integers. both arguments
-  # must be non-negative 32-bit integers.
-  subtraction32: (n1, n2) ->
-    if n1 < n2
-      @unsigned32((0x100000000 - (n2 - n1)) % 0xffffffff)
-    else
-      n1 - n2
+  # return a random integer 0 <= n < @modulo
+  randn: ->
+    # new_seed = (a * seed + c) % m
+    @seed = (@multiplier*@seed + @offset) % @modulo
 
-  # emulates overflow of adding two 32-bit integers. both arguments must be
-  # non-negative 32-bit integers.
-  addition32: (n1, n2) -> @unsigned32((n1 + n2) & 0xffffffff)
+ # return a random float 0 <= f < 1.0
+  randf: ->
+    this.randn() / @modulo
 
-  # emulates overflow of multiplying two 32-bit integers. both arguments must
-  # be non-negative 32-bit integers.
-  multiplication32: (n1, n2) ->
-    sum = 0
-    for i in [0...32]
-      if ((n1 >>> i) & 0x1)
-        sum = @addition32(sum, @unsigned32(n2 << i))
-    sum
+  # return a random int 0 <= f < n
+  rand: (n) ->
+    Math.floor(this.randf() * n)
 
-  setSeed: (seed) ->
-    if !seed || typeof seed == "number"
-      @seedWithInteger seed
-    else
-      @seedWithArray seed
-
-  defaultSeed: ->
-    currentDate = new Date()
-    currentDate.getMinutes() * 60000 + currentDate.getSeconds() * 1000 + currentDate.getMilliseconds()
-
-  seedWithInteger: (seed) ->
-    @seed = seed ? @defaultSeed()
-    @mt[0] = @unsigned32(@seed & 0xffffffff)
-    @mti = 1
-
-    while @mti < @N
-      @mt[@mti] = @addition32(
-        @multiplication32(1812433253, @unsigned32(@mt[@mti-1] ^ (@mt[@mti-1] >>> 30))),
-        @mti)
-      @mti[@mti] = @unsigned32(@mt[@mti] & 0xffffffff)
-      @mti++
-
-  seedWithArray: (key) ->
-    @seedWithInteger 19650218
-
-    i = 1
-    j = 0
-    k = if @N > key.length then @N else key.length
-
-    while k > 0
-      _m = @multiplication32(@unsigned32(@mt[i-1] ^ (@mt[i-1] >>> 30)), 1664525)
-      @mt[i] = @addition32(@addition32(@unsigned32(@mt[i] ^ _m), key[j]), j)
-      @mt[i] = @unsigned32(@mt[i] & 0xffffffff)
-
-      i++
-      j++
-
-      if i >= @N
-        @mt[0] = @mt[@N-1]
-        i = 1
-
-      j = 0 if j >= key.length
-      k--
-
-    k = @N - 1
-    while k > 0
-      @mt[i] = @subtraction32(
-        @unsigned32(@mt[i] ^ @multiplication32(@unsigned32(@mt[i-1] ^ (@mt[i-1] >>> 30)), 1566083941)), i)
-      @mt[i] = @unsigned32(@mt[i] & 0xffffffff)
-      i++
-      if i >= @N
-        @mt[0] = @mt[@N-1]
-        i = 1
-
-    @mt[0] = 0x80000000
-
-  nextInteger: (upper) ->
-    return 0 if (upper ? 1) < 1
-
-    mag01 = [0, @MATRIX_A]
-
-    if @mti >= @N
-      kk = 0
-
-      while kk < @N - @M
-        y = @unsigned32((@mt[kk] & @UPPER_MASK) | (@mt[kk+1] & @LOWER_MASK))
-        @mt[kk] = @unsigned32(@mt[kk+@M] ^ (y >>> 1) ^ mag01[y & 0x1])
-        kk++
-
-      while kk < @N-1
-        y = @unsigned32((@mt[kk] & @UPPER_MASK) | (@mt[kk+1] & @LOWER_MASK))
-        @mt[kk] = @unsigned32(@mt[kk+@M-@N] ^ (y >>> 1) ^ mag01[y & 0x1])
-        kk++
-
-      y = @unsigned32((@mt[@N-1] & @UPPER_MASK) | (@mt[0] & @LOWER_MASK))
-      @mt[@N-1] = @unsigned32(@mt[@M-1] ^ (y >>> 1) ^ mag01[y & 0x1])
-      @mti = 0
-
-    y = @mt[@mti++]
-
-    y = @unsigned32(y ^ (y >>> 11))
-    y = @unsigned32(y ^ ((y << 7) & 0x9d2c5680))
-    y = @unsigned32(y ^ ((y << 15) & 0xefc60000))
-
-    @unsigned32(y ^ (y >>> 18)) % (upper ? 0x100000000)
+  # return a random int min <= f < max
+  randRange: (min, max) ->
+    min + this.rand(max-min)
 
   randomInt: (upper) ->
-    @nextInteger(upper)
-
-  nextFloat: -> @nextInteger() / 0xffffffff
-
-  nextBoolean: -> @nextInteger() % 2 == 0
+    @rand(upper)
   
   # Returns the result of rolling *n* dice with *dx* sides, and adding *plus*.
   dice: (n, dx, plus) ->
     result = 0
     for i in [0..n]
       console.log i
-      result += @nextInteger(1, dx)
+      result += 1 + @randRange(1,dx)
     if (plus)
       result += plus
     result

src/salet.coffee

@@ -417,10 +417,8 @@ class Salet
           console.error err
       else
         currentDate = new Date()
-        @progress.seed = currentDate.getMinutes() * 60000
-        @progress.seed += currentDate.getSeconds() * 1000
-        @progress.seed += currentDate.getMilliseconds()
-        @rnd = new Random(@progress.seed)
+        @rnd = new Random()
+        @progress.seed = @rnd.getSeed()
 
         @progress.sequence = [{link:@start, when:0}]