On Wed, Aug 11, 2010 at 7:43 PM, Tim Vandermeersch <[email protected]> wrote: > Hi, > > While reading some material on Monte Carlo simulations I came across a > simple method to test a random number generator. You can generate N > numbers and plot them in 2D by using one random number as x coordinate > and another as y. For a good random generator the scatter plot will > look random. However, OBRandom does not do very well. The plot from > OBRandom looks like the text book example of a bad random number > generator. The points lie on a small number of lines as can be seen in > the images linked below.
I noticed this too a while ago. I was generating crystal structures from random fractional coordinates, and all the atoms lined up in parallel planes within the fractional cell. I quickly switched back to the stdlib implementation :-) > I haven't tested rand() but since this > depends on the system used, this is not really a portable solution. I've always wondered why OBRandom exists -- I would assume that the built in standard random number generators would be decent on each platform? Is it common to rewrite random number generators? Perhaps we should take a look at the common implementations with the same test and then just use stdlib if they're ok. My guess is that if a C implementation uses a bad random number generator, it's probably not good to use for any sort of computation... Dave ------------------------------------------------------------------------------ This SF.net email is sponsored by Make an app they can't live without Enter the BlackBerry Developer Challenge http://p.sf.net/sfu/RIM-dev2dev _______________________________________________ OpenBabel-Devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/openbabel-devel
