C ++ library study notes -- generate a set of random numbers

When trying to use

Srand (time (0 ))

Rand ()

When a random number is generated, many of the generated numbers are "same ".

Tested: srand (seed); rand () generates a random number. When seed is the same, the random number is the same.

Therefore, the above "same" problem should be caused by time (0)

So the final method is: sleep + high-precision timing, + srand (gettime_function) + rand ()

However,

[Cpp] view plaincopyprint? Changing gettimeofday to higher precision may result in better results

Changing gettimeofday to higher precision may result in better results

 

The Code is as follows (in Linux)

 

 include <stdlib.h> // for srand  #include <limits>  #include <time.h>   // for nanosleep  #include <sys/time.h>   // for gettimeofday #include <stdlib.h> // for srand#include <limits>#include <time.h>   // for nanosleep#include <sys/time.h>   // for gettimeofday

 

generate random number between 0~1  inline float randf(void) {     struct timespec tim;     tim.tv_sec=0; tim.tv_nsec=1e4;     nanosleep(&tim, 0);     struct timeval cur;     gettimeofday(&cur, 0);     srand(cur.tv_usec);     return rand()/float(RAND_MAX); }  inline int randi(int max=1e6) {     struct timespec tim;     tim.tv_sec=0; tim.tv_nsec=1e4     nanosleep(&tim, 0);     struct timeval cur;     gettimeofday(&cur, 0);     srand(cur.tv_usec);      return rand()%(max+1); } /// generate random number between 0~1inline float randf(void){    struct timespec tim;    tim.tv_sec=0; tim.tv_nsec=1e4;    nanosleep(&tim, 0);    struct timeval cur;    gettimeofday(&cur, 0);    srand(cur.tv_usec);    return rand()/float(RAND_MAX);}inline int randi(int max=1e6){    struct timespec tim;    tim.tv_sec=0; tim.tv_nsec=1e4    nanosleep(&tim, 0);    struct timeval cur;    gettimeofday(&cur, 0);    srand(cur.tv_usec);    return rand()%(max+1);}

Result: