Forum ‹ C# ‹ Random generator acting weird

[GBurg]

Hi all,

I have a weird problem. I have the following code:

void test() {
Random r = new Random();
Console.WriteLine(r.NextDouble());
Console.WriteLine(r.NextDouble());
}

test();
test();
test();
test();
test();

Each time test is called, 2 random numbers are generated. The first number is very small < 0.02, while the other is just between 0 and 1 .

What do I miss, and how to make the first number normal (between 0 and 1, not between 0 and 0.02)?

[Henrik]

When you create a new Random instance, it will have a seed, and if you have two instances with the same seed, they will produce the exact same sequence of random numbers.

If you instantiate a Random without any parameters, the seed defaults to the system time, and if you make five calls right after the other, some of those will have the same seed since the calls will come in faster than the system time changes.

The solution is of course to not create new instances of Random all the time. Make one and keep it for a while.

[Henrik]

Code: Select all

public Random r = new Random();

public void Test() {
   Console.WriteLine(r.NextDouble());
   Console.WriteLine(r.NextDouble());
}

[GBurg]

Using only one random instance indeed solved my problem. thanks!