Related idea: if we're now on Commons 3.1, I can back-port changes from Myrrix to use Commons Math's Mersenne Twister RNG. I found it faster and more thread-friendly, and would let us get rid of the Uncommons Math dependency. Commons Math's RNG plays nicer with its own classes, which we are using.
On Wed, Jan 2, 2013 at 9:59 AM, Sean Owen <[email protected]> wrote: > It passes for me. It's asserting about the result of a random process though. > > 10% of 1000 elements are sampled, and the number sampled should be > normally distributed with mean 100 and stdev ~= sqrt(0.9*0.1*1000). > The test asserts it's within 4 standard deviations which should only > fail about 1 out of 16,000 times. This is run 1000 times. > > I suppose it wouldn't be so strange for it to fail eventually, since > it will over time be run tens of thousands of times. The thing is, the > tests are supposed to always start from the same random seed state, so > should be deterministic. > > But then: a short while ago I cleverly optimized this iterator by > having it pick the # of elements to skip from a geometric distribution > instead of actually checking a probability a bunch of times. > > But then: Commons Math's implementation doesn't let you supply a > random number generator, so it's internally using its own > non-deterministically seeded RNG, and that may allow different test > results. > > But then: in 3.1, released last week, you can supply your own RNG. > > I think I will fix this by updating to 3.1 and supplying our RNG, and > also loosening the test bounds a bit. > > On Wed, Jan 2, 2013 at 9:11 AM, Dan Filimon <[email protected]> > wrote: >> Sorry if you know about this, but the >> testSample(org.apache.mahout.cf.taste.impl.common.SamplingLongPrimitiveIteratorTest) >> fails at line 77, >> assertTrue(k <= 100 + 4 * sd); >> >> I changed a bunch of code in Mahout (unrelated to this test) and >> Jenkins doesn't seem to point to any failed tests in the last stable >> build [1]. Trunk currently seems to fail building not sure why...). >> >> Could anyone check to see if they can reproduce this test failing? >> Thanks! >> >> [1] >> https://builds.apache.org/job/Mahout-Quality/lastSuccessfulBuild/testReport/
