Just another update

Task/Miller-Rabin-primality-test/JavaScript/miller-rabin-primality-test.js

@@ -1,31 +1,33 @@
-function modProd(a,b,n){
-  if(b==0) return 0;
-  if(b==1) return a%n;
-  return (modProd(a,(b-b%10)/10,n)*10+(b%10)*a)%n;
-}
-function modPow(a,b,n){
-  if(b==0) return 1;
-  if(b==1) return a%n;
-  if(b%2==0){
-    var c=modPow(a,b/2,n);
-    return modProd(c,c,n);
-  }
-  return modProd(a,modPow(a,b-1,n),n);
-}
-function isPrime(n){
-  if(n==2||n==3||n==5) return true;
-  if(n%2==0||n%3==0||n%5==0) return false;
-  if(n<25) return true;
-  for(var a=[2,3,5,7,11,13,17,19],b=n-1,d,t,i,x;b%2==0;b/=2);
-  for(i=0;i<a.length;i++){
-    x=modPow(a[i],b,n);
-    if(x==1||x==n-1) continue;
-    for(t=true,d=b;t&&d<n-1;d*=2){
-      x=modProd(x,x,n); if(x==n-1) t=false;
-    }
-    if(t) return false;
-  }
-  return true;
-}
+function probablyPrime(n, k) {
+	if (n === 2 || n === 3)
+		return true;
+	if (n % 2 === 0 || n < 2)
+		return false;
 
-for(var i=1;i<=1000;i++) if(isPrime(i)) console.log(i);
+	// Write (n - 1) as 2^s * d
+	var s = 0, d = n - 1;
+	while (d % 2 === 0) {
+		d /= 2;
+		++s;
+	}
+
+	WitnessLoop: do {
+		// A base between 2 and n - 2
+		var x = Math.pow(2 + Math.floor(Math.random() * (n - 3)), d) % n;
+
+		if (x === 1 || x === n - 1)
+			continue;
+
+		for (var i = s - 1; i--;) {
+			x = x * x % n;
+			if (x === 1)
+				return false;
+			if (x === n - 1)
+				continue WitnessLoop;
+		}
+
+		return false;
+	} while (--k);
+
+	return true;
+}