Rand () sowing with a time problem ()

Question

I find it difficult to understand how to use rand () and sow it with time () using Xcode. I want to generate random decimal numbers from 0 to 1.

The code gives me seemingly random numbers for elements 1 and 2, but element 0 is always somewhere around 0.077. Any ideas why this would be?

My code is:

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int main(void)
{
double array[3];

double rand_max = RAND_MAX;

srand((int)time(NULL));

for (int iii = 0; iii < 3; iii++)
    array[iii] = rand() / rand_max;

for (int iii = 0; iii < 3; iii++)
    printf("Element %d is: %lf.\n", iii, array[iii]);

return(0);
}

The output for several runs was as follows:

[Session started at 2010-09-11 21:19:07 -0500.]

Element 0 is: 0.076918.

Element 1 is: 0.753664.

Element 2 is: 0.824467.

The Debugger has exited with status 0.
[Session started at 2010-09-11 21:19:12 -0500.]
Element 0 is: 0.076957.
Element 1 is: 0.411353.
Element 2 is: 0.602494.

The Debugger has exited with status 0.

[Session started at 2010-09-11 21:19:16 -0500.]

Element 0 is: 0.076988.

Element 1 is: 0.937504.

Element 2 is: 0.624915.

The Debugger has exited with status 0.

[Session started at 2010-09-11 21:19:24 -0500.]

Element 0 is: 0.077051.

Element 1 is: 0.989806.

Element 2 is: 0.669757.

Answer 1

try a random random generator without dropping it in

/* initialize random seed: */
srand ( time(NULL) );

---

Holly pray ... it's not easy. I remember for a long time in my stochastic models, I had this problem. As far as I remember, the solution was to use some kind of pragma-derivative.

, . ... .

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int main(void)
{
    double array[10];

    double rand_max = RAND_MAX;

    srand(time(NULL));

    for (int iii = 0; iii < 9; iii++){
        rand();
        array[iii] = rand() / rand_max;
    }

    for (int iii = 0; iii < 9; iii++){
        printf("Element %d is: %lf.\n", iii, array[iii]);
    }


    return(0);
}

Answer 2

rand . , . .: . comp.lang.c.

Answer 3

rand() . , rand-fbsd.c. time() , .

random() . sranddev() srandomdev().