xgcl/grand/drng/entropy/rdtsc/cputime.md

In linux

#include <pthread.h>
#include <stdio.h>
#include <time.h>
#include <stdint.h>

static long long GetThreadCpuTimeNs() {
    struct timespec t;
    if (clock_gettime(CLOCK_THREAD_CPUTIME_ID, &t)) {
        perror("clock_gettime");
        return 0;
    }
    return t.tv_nsec;
}

Makov测试熵估计0.5-0.6