On Sat, Dec 28, 2013 at 12:45 PM, Lee Spector <lspec...@hampshire.edu>wrote:
> > On Dec 28, 2013, at 11:27 AM, Cedric Greevey wrote: > > > > It helps to go with the "functional, immutable" flow, in which case if > you get an unwanted exception it should *usually* have bubbled up from some > failing test. Add a dump-locals where suggested by the stack trace and > rerun the failing test and voila! That should do it for almost all > non-exogenous exceptions, leaving mainly things like network timeouts and > other wonkiness caused by factors outside of your code (and, often, outside > of your control anyway). > > You've given me some interesting things to think about re: the role of > testing, but I think that it may be hard to map your approach directly on > to the kind of work that I do. > > I often work with stochastic simulations which run for days and for which > repeatability is hard to engineer, especially in a multicore context. > There's a lot of unpredictable dynamism and usually code is generated and > run dynamically (and mutated and recombined; this is "genetic > programming"). Even if you code functionally and immutably (which I try to > do, to a reasonable extent), and stamp out all nondeterminism (which would > be a pain), it may take days to re-create a situation. > Your requirements are unusual. That being said, you might want to consider: 1. Using a PRNG with recordable seed, and sane concurrency semantics, to achieve repeatability -- rerun with same seed to get identical replay of events. 2. If crashes are happening after days, add snapshotting -- some ability to save the state of the whole simulation from time to time (including current PRNG state). Use the last snapshot before a crash to investigate the crash. Requires item 1, above, for rerunning from the same snapshot to produce unvarying results. I'd suggest using a ref world, with a periodically waking thread that does a (spit (dosync (dump-all-the-refs-to-some-data-structure))) or something. (If retries become a big problem you'll need to add more coordination, maybe using core.async to get everything else to take a breather during each state dump.) You also need order-independence (which suggests a deterministic breaking up of the world into the domains of different threads, with defined interaction channels and times, and a separate PRNG per thread -- I'd suggest a state-dumpable Mersenne Twister instance per thread, seeded at startup using values from java.util.Random, itself seeded with a known startup seed). -- -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
