On Apr 23, 2015, at 11:05 AM, Steve Smaldone <smald...@gmail.com> wrote:
> On Thu, Apr 23, 2015 at 6:34 AM, Cem Karan <cfkar...@gmail.com> wrote: > > On Apr 23, 2015, at 1:59 AM, Steven D'Aprano > <steve+comp.lang.pyt...@pearwood.info> wrote: > > > On Thursday 23 April 2015 11:53, Cem Karan wrote: > > > >> Precisely. In order to make my simulations more realistic, I use a lot of > >> random numbers. I can fake things by keeping the seed to the generator, > >> but if I want to do any sort of hardware in the loop simulations, then > >> that approach won't work. > > > > That's exactly why we have *pseudo* random number generators. They are > > statistically indistinguishable from "real" randomness, but repeatable when > > needed. > > Which is why is why I mentioned keeping the seed above. The problem is that > I eventually want to do hardware in the loop, which will involve IO between > the simulation machine and the actual robots, and IO timing is imprecise and > uncontrollable. That is where not recording something becomes lossy. That > said, the mere act of trying to record everything is going to cause timing > issues, so I guess I'm over thinking things yet again. > > Thanks for the help everyone, its helped me clarify what I need to do in my > mind. > > > Well, you could achieve this on Linux by using the rdiff library. Not > exactly a purely Python solution, but it would give you file-based diffs. > > Basically, what you could do is write the first file. Then for each > subsequent saves, write out the file (as a temp file) and issue shell > commands (via the Python script) to calculate the diffs of the new file > against the first (basis) file. Once you remove the temp files, you'd have a > full first save and a set of diffs against that file. You could rehydrate > any save you want by applying the diff to the basis. > > If you work on it a bit, you might even be able to avoid the temp file saves > by using pipes in the shell command. > > Of course, I haven't tested this so there may be non-obvious issues with > diffing between subsequent pickled saves, but it seems that it should work on > the surface. That might work... although I'm running on OS X right now, once I get to the hardware in the loop part, it's all going to be some flavor of Linux. I'll look into it... thanks! Thanks, Cem Karan -- https://mail.python.org/mailman/listinfo/python-list
