Look at the harvestr package for one way to control multiple parallel simulations and make sure that they have different seeds.
On Wed, Feb 20, 2013 at 4:24 PM, C W <tmrs...@gmail.com> wrote: > Thanks, Greg. I think you are right. I did simulation one right after > the other, less than 2 seconds. > > But still, it was shocking to see identical samples, which I had to throw > away. > > As a rule of thumb, should I do simulation in one R console, rather than > splitting the work into 2 consoles. I just thought it would take less time > for me, but it seems risky. > > Thanks, > Mike > > > > On Wed, Feb 20, 2013 at 6:13 PM, Greg Snow <538...@gmail.com> wrote: > >> To know for sure we need to know how you are running these different R >> sessions, but here are some possibilities: >> >> The help page for "set.seed" says that if no seed exists then the seed is >> set based on the current time (and since 2.14.0 the process ID). So one >> possibility is that 2 of the sessions are started close enough together >> that they get the same seed. Or the difference in time and process ID >> cancel each other out. >> >> Another possibility (also mentioned in the help page) is that if the seed >> was saved in a previous session then it will be restored in the new >> session, if all the sessions are reading in the same stored session (or >> just the 2 that are the same) then they would start from the same seed. >> >> >> On Tue, Feb 19, 2013 at 6:31 PM, C W <tmrs...@gmail.com> wrote: >> >>> Hi, list >>> I am doing 100,000 iterations of Bayesian simulations. >>> >>> What I did is I split it into 4 different R sessions, each one runs >>> 25,000 >>> iteration. But two of the sessions gave the simulation result. >>> >>> I did not use any set.seed(). What is going on here? >>> >>> Thanks, >>> Mike >>> >>> [[alternative HTML version deleted]] >>> >>> >>> ______________________________________________ >>> R-help@r-project.org mailing list >>> https://stat.ethz.ch/mailman/listinfo/r-help >>> PLEASE do read the posting guide >>> http://www.R-project.org/posting-guide.html >>> and provide commented, minimal, self-contained, reproducible code. >>> >> >> >> >> -- >> Gregory (Greg) L. Snow Ph.D. >> 538...@gmail.com >> > > -- Gregory (Greg) L. Snow Ph.D. 538...@gmail.com [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
