|Message: Re: Random generator correlation on quad-core PC||Not Logged In (login)|
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On Fri, 8 Jun 2007, Ilya wrote: > *** Discussion title: Run Management > Email replies to PublicHyperNews@slac.stanford.edu must include: > In-Reply-To: <"/runmanage/189"@geant4-hn.slac.stanford.edu> > Subject: ...change this to be about your reply. > > Dear all, > > I have encountered a problem for which I don't see immediate solution. I > am running 4 instances of one simulation program on a quad-core PC. > These simulations use each different random seed numbers that are > restored from different files in the beginning of run (similar as in > /examples/novice/N03). I am using the defaul random generator. > > Normally if I run the simulations on different PC's I get perfectly > uncorrelated outputs. But after looking at the results obtained in 4 > simulations on quad-core PC I found that the outputs are almost > identical (only few events out of 3e6 are different). > > I start the simulations within about 1 min time interval. > > Can somebody explain why this happens (I guess it is due to some > correlation of random generators but why...?)? And how to avoid this > correlation? > > I am using GEANT4.8.2.p1 under SUSE Linux > > Thanks a lot for help, Ilya. > Hello, If you use saving of random numbers per event and restore random numbers from file you share the same file for all processes. In that case you need run 4 applications from different subdirectories. VI
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