On Wed, Nov 14, 2012 at 04:38:47PM -0800, Phil Steitz wrote: > On 11/14/12 4:05 PM, Gilles Sadowski wrote: > > Hi. > > > > On Wed, Nov 14, 2012 at 08:09:52PM -0000, t...@apache.org wrote: > >> Author: tn > >> Date: Wed Nov 14 20:09:51 2012 > >> New Revision: 1409352 > >> > >> URL: http://svn.apache.org/viewvc?rev=1409352&view=rev > >> Log: > >> Reduce sleep time in unit test to prevent possible race condition. > >> > >> Modified: > >> > >> commons/proper/math/trunk/src/test/java/org/apache/commons/math3/genetics/FixedElapsedTimeTest.java > >> > >> Modified: > >> commons/proper/math/trunk/src/test/java/org/apache/commons/math3/genetics/FixedElapsedTimeTest.java > >> URL: > >> http://svn.apache.org/viewvc/commons/proper/math/trunk/src/test/java/org/apache/commons/math3/genetics/FixedElapsedTimeTest.java?rev=1409352&r1=1409351&r2=1409352&view=diff > >> ============================================================================== > >> --- > >> commons/proper/math/trunk/src/test/java/org/apache/commons/math3/genetics/FixedElapsedTimeTest.java > >> (original) > >> +++ > >> commons/proper/math/trunk/src/test/java/org/apache/commons/math3/genetics/FixedElapsedTimeTest.java > >> Wed Nov 14 20:09:51 2012 > >> @@ -59,7 +59,7 @@ public class FixedElapsedTimeTest { > >> > >> while (!tec.isSatisfied(pop)) { > >> try { > >> - Thread.sleep(500); > >> + Thread.sleep(50); > >> } catch (InterruptedException e) { > >> // ignore > >> } > >> > > I have never read this part of CM yet. But just this makes me think that the > > "FixedElapsedTime" class should not exist in CM. Indeed, using it makes the > > algorithm behave differently at each run! > > I don't deny the usefulness of allotting some amount of time for a > > computation, but this has absolutely nothing to do with genetic algorithms > > (nor any others). > > CM can help in implementing this high-level requirement, by allowing > > <some search algorithm> to be restarted with the result of a previous run > > but IMHO it is a bad idea to have the various CM codes directly implement > > that functionality. > > I disagree. This looks like a useful feature to me, contributed by > a user. GA algorithms are by nature iterative with run-time > evaluated StoppingConditions. FixedElapsedTime is a reasonable > stopping condition supported by other GA frameworks. The feature is > well-documented, so users know exactly what it does. In particular, > the number of generations is not fixed, so using this > StoppingCondition does not guarantee the same results on successive > runs with the same input parameters. GAs are often > non-deterministic for other reasons (randomness in mutation), so > this is not a practical issue for those choosing to use the feature. >
This one is really not worth a fight, but something which you have to adapt depending on the machine on which you run your program can only be qualified as a toy feature (IMHO): Unless we talk about real-time processing (which GA are not really suited for...), some fixed amount of time can be too small (solution not found on a "slow" machine) or too large (solution found long before the end of the alloted time slot, but the algo keeps the CPU busy). As for "non-deterministic", we had several discussions on this ML about being able to control the pseudo-random behaviour of the algorithms, by using a fixed seed. This is the same here, should you use the same seed, the search should go through the same steps. But in this case, it is _impossible_ to reproduce the same result since the number of generations will depend on how busy the machine is with other processes. Gilles --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org For additional commands, e-mail: dev-h...@commons.apache.org
