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Move ceil call back into the geometric sampler.

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Test exactly what the geometric sampler returns, because that's what
the downstream callers of it are going to use.

While here, also assert that the geometric sampler returns a positive
integer.  (Our geometric distribution is the one suported on {1, 2,
3, ...} that returns the number of trials before the first success,
not the one supported on {0, 1, 2, ...} that returns the number of
failures before the first success.)
This commit is contained in:
Taylor R Campbell 2019-01-10 17:12:56 +00:00 committed by George Kadianakis
parent 948856c03e
commit 531df9590d
2 changed files with 12 additions and 2 deletions
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2
src/lib/math/prob_distr.c
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@ -1308,7 +1308,7 @@ sample_geometric(uint32_t s, double p0, double p)
if (p >= 1)
return 1;
return (-x/log1p(-p));
return ceil(-x/log1p(-p));
}
/*******************************************************************/

12
src/test/test_prob_distr.c
View File

@ -958,7 +958,17 @@ test_stochastic_geometric_impl(double p)
size_t C[PSI_DF] = {0};
for (j = 0; j < NSAMPLES; j++) {
double n_tmp = ceil(geometric_sample(p));
double n_tmp = geometric_sample(p);
/* Must be an integer. (XXX -Wfloat-equal) */
tor_assert(ceil(n_tmp) <= n_tmp && ceil(n_tmp) >= n_tmp);
/* Must be a positive integer. */
tor_assert(n_tmp >= 1);
/* Probability of getting a value in the billions is negligible. */
tor_assert(n_tmp <= (double)UINT_MAX);
unsigned n = (unsigned) n_tmp;
if (n > PSI_DF)