Commit a5df9402 authored by George Kadianakis's avatar George Kadianakis Committed by Nick Mathewson
Browse files

prob-distr: Decrease false positive rate of stochastic tests.

parent 3871fb73
o Minor bugfixes (unit tests):
- Decrease the false positive rate of stochastic probability distribution
tests. Fixes bug 29693; bugfix on 0.4.0.1-alpha.
\ No newline at end of file
......@@ -878,11 +878,14 @@ test_uniform_interval(void *arg)
* is higher: 1 - Binom(0; n, alpha) = 1 - (1 - alpha)^n. For n = 10,
* this is about 10%, and for n = 100 it is well over 50%.
*
* We can drive it down by running each test twice, and accepting it if
* it passes at least once; in that case, it is as if we used Binom(2;
* 2, alpha) = alpha^2 as the false positive rate for each test, and
* for n = 10 tests, it would be 0.1%, and for n = 100 tests, still
* only 1%.
* Given that these tests will run with every CI job, we want to drive down the
* false positive rate. We can drive it down by running each test four times,
* and accepting it if it passes at least once; in that case, it is as if we
* used Binom(4; 2, alpha) = alpha^4 as the false positive rate for each test,
* and for n = 10 tests, it would be 9.99999959506e-08. If each CI build has 14
* jobs, then the chance of a CI build failing is 1.39999903326e-06, which
* means that a CI build will break with probability 50% after about 495106
* builds.
*
* The critical value for a chi^2 distribution with 100 degrees of
* freedom and false positive rate alpha = 1% was taken from:
......@@ -895,7 +898,7 @@ test_uniform_interval(void *arg)
static const size_t NSAMPLES = 100000;
/* Number of chances we give to the test to succeed. */
static const unsigned NTRIALS = 2;
static const unsigned NTRIALS = 4;
/* Number of times we want the test to pass per NTRIALS. */
static const unsigned NPASSES_MIN = 1;
......
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