kolibrios/programs/develop/ktcc/trunk/libctest/rand.inc
siemargl ace23ebbe2 libc testsuite + fixes
git-svn-id: svn://kolibrios.org@6433 a494cfbc-eb01-0410-851d-a64ba20cac60
2016-05-19 12:15:22 +00:00

168 lines
2.7 KiB
C++

#include <float.h>
// TODO: use large period prng
static uint64_t seed = -1;
static uint32_t rand32(void)
{
seed = 6364136223846793005ULL*seed + 1;
return seed >> 32;
}
static uint64_t rand64(void)
{
uint64_t u = rand32();
return u<<32 | rand32();
}
static double frand()
{
return rand64() * 0x1p-64;
}
static float frandf()
{
return rand32() * 0x1p-32f;
}
static long double frandl()
{
return rand64() * 0x1p-64L
#if LDBL_MANT_DIG > 64
+ rand64() * 0x1p-128L
#endif
;
}
void t_randseed(uint64_t s)
{
seed = s;
}
/* uniform random in [0,n), n > 0 must hold */
uint64_t t_randn(uint64_t n)
{
uint64_t r, m;
/* m is the largest multiple of n */
m = -1;
m -= m%n;
while ((r = rand64()) >= m);
return r%n;
}
/* uniform on [a,b], a <= b must hold */
uint64_t t_randint(uint64_t a, uint64_t b)
{
uint64_t n = b - a + 1;
if (n)
return a + t_randn(n);
return rand64();
}
/* shuffle the elements of p and q until the elements in p are well shuffled */
static void shuffle2(uint64_t *p, uint64_t *q, size_t np, size_t nq)
{
size_t r;
uint64_t t;
while (np) {
r = t_randn(nq+np--);
t = p[np];
if (r < nq) {
p[np] = q[r];
q[r] = t;
} else {
p[np] = p[r-nq];
p[r-nq] = t;
}
}
}
/* shuffle the elements of p */
void t_shuffle(uint64_t *p, size_t n)
{
shuffle2(p,0,n,0);
}
void t_randrange(uint64_t *p, size_t n)
{
size_t i;
for (i = 0; i < n; i++)
p[i] = i;
t_shuffle(p, n);
}
/* hash table insert, 0 means empty, v > 0 must hold, len is power-of-2 */
static int insert(uint64_t *tab, size_t len, uint64_t v)
{
size_t i = v & (len-1);
size_t j = 1;
while (tab[i]) {
if (tab[i] == v)
return -1;
i += j++;
i &= len-1;
}
tab[i] = v;
return 0;
}
/* choose k unique numbers from [0,n), k <= n */
int t_choose(uint64_t n, size_t k, uint64_t *p)
{
uint64_t *tab;
size_t i, j, len;
if (n < k)
return -1;
if (n < 16) {
/* no alloc */
while (k)
if (t_randn(n--) < k)
p[--k] = n;
return 0;
}
if (k < 8) {
/* no alloc, n > 15 > 2*k */
for (i = 0; i < k;) {
p[i] = t_randn(n);
for (j = 0; p[j] != p[i]; j++);
if (j == i)
i++;
}
return 0;
}
// TODO: if k < n/k use k*log(k) solution without alloc
if (n < 5*k && (n-k)*sizeof *tab < (size_t)-1) {
/* allocation is n-k < 4*k */
tab = malloc((n-k) * sizeof *tab);
if (!tab)
return -1;
for (i = 0; i < k; i++)
p[i] = i;
for (; i < n; i++)
tab[i-k] = i;
if (k < n-k)
shuffle2(p, tab, k, n-k);
else
shuffle2(tab, p, n-k, k);
free(tab);
return 0;
}
/* allocation is 2*k <= len < 4*k */
for (len = 16; len < 2*k; len *= 2);
tab = calloc(len, sizeof *tab);
if (!tab)
return -1;
for (i = 0; i < k; i++)
while (insert(tab, len, t_randn(n)+1));
for (i = 0; i < len; i++)
if (tab[i])
*p++ = tab[i]-1;
free(tab);
return 0;
}