MersenneTwister重复数字

Question

I have to create a random sequence of number using MersenneTwister (I can't change algorithm). Different calls to the generation algorithm always gives the same results after the first three attempts. Here is the code:

var getRandomArray=function(length){
    var casuals=[];
    var mersenneTwister = new MersenneTwister(new Date().getTime()/2); //A SEED TEST
    while(casuals.length < length){
        var vmt= mersenneTwister.random();
        var newVal= Math.round( vmt*100);
        if(casuals.indexOf(newVal)===-1) 
            casuals.push(newVal);
    }
    //casuals.sort(function(a,b){return a-b;});//NUMERIC SORT
    return casuals;
};

var inputs1= getRandomArray(6);
var inputs2= getRandomArray(6);
//inputs1 AND inputs2 ARE ALWAYS THE SAME!

I tried changing different kind of seed but nothing changes. I created here a fiddle .

Here the algorithm I downloaded.

Am I missing something?

Answer 1

It is because you are using new Date().getTime() . The twister function finishes very quickly, to two successive calls to new Date().getTime() give the same value, thus the same seed.

If you add a different number, eg such as this:

• http://jsfiddle.net/vcpjdo94/3/

it works as expected.

The changes are:

$scope.genRandom=function(){
    $scope.inputs1= getRandomArray(6, 1);
    $scope.inputs2= getRandomArray(6, 2);
};

and:

var getRandomArray=function(length, add){
    var casuals=[];
    var mersenneTwister = new MersenneTwister(new Date().getTime()/2 + add);
...
}

ie addition of add parameter.