Difference between RooRandom and Random

[Xola]

Hi guys.

I am trying to generate random numbers using a specific seed. Was toying around with the code a bit to see if I can get the same numbers if I use the same seed for RooRandom::randomGenerator->Gaus(mean, sigma) and gRandom->Gaus(mean, sigma). Just wanted to find out what the difference between the two is because I dont get the same numbers even if I do

RooRandom::randomGenerator->SetSeed(seed)

and

gRandom->SetSeed(seed)

Here is a sample of the code that I am using:

  while(1) {
                        xgen = gRandom->Gaus(gaus->x,gaus->sigma);
//                        xgen = gaus->x + gaus->sigma *result;
                        if (xgen<gaus->mean.max() && xgen>gaus->mean.min()) {
                            gaus->mean = xgen ;
                            cout << "Gaussian -> "<< xgen << endl;

                            break;
                        }
                    }

or

            while(1) {
                    cout << "this is the seed "<< gRandom->fSeed << endl;
                        xgen = RooRandom::randomGenerator()->Gaus(gaus->x,gaus->sigma);
//                        xgen = gaus->x + gaus->sigma *result;
                        if (xgen<gaus->mean.max() && xgen>gaus->mean.min()) {
                            gaus->mean = xgen ;
                            cout << "Gaussian -> "<< xgen << endl;

                            break;
                        }
                    }

Thanks in advance

[StephanH]

Hi @Xola,

check the code by clicking on the line number here. RooRandom uses TRandom3.
gRandom is probably also a TRandom3, but you have to check. Try to print it:
gRandom->Print().

If they are the same, you just have to give them the same seeds. Check by printing the seeds. Note that a seed of 0 means random seed.