Random random = new Random();
int rand = random.Next(6);
It seems to repeat some numbers quite frequently though. What I'm wanting to know is if there's a better way to generate random numbers that seems more... random?
You're not creating a new Random instance everytime are you? Each Random instance starts with the same seed, unless you pass one in to the constructor, so you will get the same sequence of random numbers each time. Usually you would create and keep a Random object and then just call Next() whenever you need a number. If the problem is that you don't want the same sequence of random numbers everytime then you need to pass a new seed when you create your Random object. You could use the current time or something to get a random seed.
Cheers,
Leaf.
Also, if you are only generating numbers from 0-5, then you can hardly be surprised that the same numbers repeat alot. You should even expect them to repeat the same number consecutively frequently (about 17% of the time).
If you just want to prove to yourself that the number distribution is suitably random, then generate a couple thousand numbers, keeping track of the results, and then compare how many times you got each number.
Leaf. wrote:
You're not creating a new Random instance everytime are you? Each Random instance starts with the same seed, unless you pass one in to the constructor, so you will get the same sequence of random numbers each time.
If you leave the parameter empty, "Random()", then the class will automatically use the timer as the seed.
You're right, it will use a timer based seed, thanks for the correction. Unfortunately that timer doesn't appear to be very high frequency, which is why people who (mistakenly) recreate Random objects for each use sometimes see repeated sequences of numbers.
Some IronPython code that show's the problem:
>>> def RunRandom():
... for i in range(10):
... r = System.Random()
... for i in range(6):
... print r.Next(6),
... print System.Environment.TickCount
...
...
>>> RunRandom()
2 2 5 2 0 5 26809625
1 1 0 4 2 0 26809640
1 1 0 4 2 0 26809640
1 1 0 4 2 0 26809640
1 1 0 4 2 0 26809640
1 1 0 4 2 0 26809640
1 1 0 4 2 0 26809640
1 1 0 4 2 0 26809640
1 1 0 4 2 0 26809640
1 1 0 4 2 0 26809640
Cheers,
Leaf.
I came across a similar issue with repetitive random seeds. I originally used this to generate new seed, but when I reused it when the code was running, the same seed was being used, and producing the same random figures.
Random
rdm = new Random((int)unchecked(DateTime.Now.Ticks));So I eventually replaced with this code, to generate different random seeds when running:
// Variable declaration.
public
override void Start() // Generate a seed value from the date time ticks. // Store the next seed value.
Random rdmSeed = new Random((int)unchecked(DateTime.Now.Ticks));
m_intRandomSeed = rdmSeed.Next();
public
void RandomNumber() // Use the first random number for the seed of the next number.
// Generate the number between 0 and 6.
int int
So calling RandomNumber each time will also produce a different set of numbers.
Each time the routine is called the Seed number is always different.
Don't know if that will help you.
I've just had a quick thought though. After reading that the number of values I'm asking for might be a problem because it's too small, would I get better results if I generated a random number between 0 and say, 446578 or 126378 or 654723 (basically just any large number) and then modded it by 6?
No. In fact you would get a worse distribution since its likely that the core random number generator creates a base number which is not a multiple of 6 so there would be a slight bias.
e.g.
lets say the random number generator creates numbers 0-255 (8 bits) and you mod the result by 6.
you will get 43x0,1,2,3 and 42x4,5 which means your random numbers are not evenly distributed
Why does nobody trust that the .Net team knew what they are doing? Your problem was correctly diagnosed by leaf and you don't need to seed it with the time becuase the default constructor does this. I'm not 100% sure what Pavcules solution is trying to do but its just not required.
Just make a single Random (I ususally do it as a static on the class - no point is having one per instance most of the time) and call the methods provided.
class foo
{
private static Random random = new Random();
private void function()
{
int i = random.Next(6);
}
}
A 100000x loop getting every value of i (random.Next(6)) and counting how many times each number came out. The diference between the max and min was below 5%, which I think is enough.
