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shared/tests: add nmtst_get_rand_word_length()

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Will be used to get a random number with a certain distribution,
that suitable to generate input values.
This commit is contained in:
Thomas Haller 2020-03-27 16:08:48 +01:00
parent 7842da1606
commit 5f6dfcfc92
1 changed files with 63 additions and 0 deletions
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63
shared/nm-utils/nm-test-utils.h
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@ -986,6 +986,69 @@ nmtst_rand_perm_gslist (GRand *rand, GSList *list)
/*****************************************************************************/
/**
* nmtst_get_rand_word_length:
* @rand: (allow-none): #GRand instance or %NULL to use the singleton.
*
* Returns: a random integer >= 0, that most frequently is somewhere between
* 0 and 16, but (with decreasing) probability, it can be larger. This can
* be used when we generate random input for unit tests.
*/
static inline guint
nmtst_get_rand_word_length (GRand *rand)
{
guint n;
if (!rand)
rand = nmtst_get_rand ();
n = 0;
while (TRUE) {
guint32 rnd = g_rand_int (rand);
guint probability;
/* The following python code implements a random sample with this
* distribution:
*
* def random_histogram(n_tries, scale = None):
* def probability(n_tok):
* import math
* return max(2, math.floor(100 / (2*(n_tok+1))))
* def n_tokens():
* import random
* n_tok = 0
* while True:
* if random.randint(0, 0xFFFFFFFF) % probability(n_tok) == 0:
* return n_tok
* n_tok += 1
* hist = []
* i = 0;
* while i < n_tries:
* n_tok = n_tokens()
* while n_tok >= len(hist):
* hist.append(0)
* hist[n_tok] = hist[n_tok] + 1
* i += 1
* if scale is not None:
* hist = list([round(x / n_tries * scale) for x in hist])
* return hist
*
* For example, random_histogram(n_tries = 1000000, scale = 1000) may give
*
* IDX: [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29]
* SEEN: [20, 39, 59, 73, 80, 91, 92, 90, 91, 73, 73, 54, 55, 36, 24, 16, 16, 8, 4, 2, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0]
*
* which give a sense of the probability with this individual results are returned.
*/
probability = NM_MAX (2u, (100u / (2u * (n + 1u))));
if ((rnd % probability) == 0)
return n;
n++;
}
}
/*****************************************************************************/
static inline gboolean
nmtst_g_source_assert_not_called (gpointer user_data)
{