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#ifdef __cplusplus
extern "C" {
#endif
#include "ulib/splitmix.h"
#include "ulib/gettime.h"
#ifdef __cplusplus
}
#endif
/* based on splitmix64
* https://xorshift.di.unimi.it/splitmix64.c
*/
void sm_srand(pUCXT, Pid_t pid) {
unsigned int n;
UV ptod[2];
/*
* The idea is to just have a unique value here,
* so system time and process id should be enough.
* (Provided system time doesn't repeat!)
*
* But, since Unix epoch time with usec resolution
* is 51 bits, that only leaves 13 bits for pid.
*
* So, lets initially seed with TOD, mix, add the PID,
* then mix again.
*/
/* gettimeofday(&tv, 0); */
(*UCXT.myU2time)(aTHX_ (UV*)&ptod);
UCXT.sm_x = (U64)ptod[0] * 1000000
+ (U64)ptod[1];
/* stir 16 - 31 times, pid-based */
n = 16 + (pid & 0x0f);
while (n-- > 0)
(void)sm_rand(aUCXT);
UCXT.sm_x ^= (U64)pid;
/* stir 16 - 31 times, time-based */
n = 16 + ((ptod[0] ^ ptod[1]) & 0x0f);
while (n-- > 0)
(void)sm_rand(aUCXT);
}
U64 sm_rand(pUCXT) {
U64 z = (UCXT.sm_x += 0x9e3779b97f4a7c15ULL);
z = (z ^ (z >> 30)) * 0xbf58476d1ce4e5b9ULL;
z = (z ^ (z >> 27)) * 0x94d049bb133111ebULL;
return z ^ (z >> 31);
}
/* ex:set ts=2 sw=2 itab=spaces: */
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