On Wed, May 18, 2016 at 4:50 PM, Chris Barker <chris.bar...@noaa.gov> wrote: >> >> > ...anyway, the real reason I'm a bit grumpy is because there are solid >> > engineering reasons why users *want* this API, > > Honestly, I am lost in the math -- but like any good engineer, I want to accomplish something anyway :-) I trust you guys to get this right -- or at least document what's "wrong" with it. > > But, if I'm reading the use case that started all this correctly, it closely matches my use-case. That is, I have a complex model with multiple independent "random" processes. And we want to be able to re-produce EXACTLY simulations -- our users get confused when the results are "different" even if in a statistically insignificant way. > > At the moment we are using one RNG, with one seed for everything. So we get reproducible results, but if one thing is changed, then the entire simulation is different -- which is OK, but it would be nicer to have each process using its own RNG stream with it's own seed. However, it matters not one whit if those seeds are independent -- the processes are different, you'd never notice if they were using the same PRN stream -- because they are used differently. So a "fairly low probability of a clash" would be totally fine.
Well, the main question is: do you need to be able to spawn dependent streams at arbitrary points to an arbitrary depth without coordination between processes? The necessity for multiple independent streams per se is not contentious. -- Robert Kern
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