C Program to Generate Random Numbers using Multiply with Carry Method

This C program generates random number using multiply with carry method. Most RNGs work by keeping a certain number, say k, of the most recently generated integers, then return the next integer as a function of those k. The initial k integers, the seeds, are assumed to be randomly chosen, usually 32-bits. The period of the RNG is related to the number of choices for seeds, usually 2^(32k), so to get longer periods you need to increase k. Here is a complimentary-multiply-with-carry RNG with k = 4097

Here is the source code of the C program to generate random number using complimentary-multiply-with-carry method with k = 4097. The C program is successfully compiled and run on a Linux system. The program output is also shown below.

```
#include <stdio.h>
```
```
#include <math.h>
```
```
#include <stdlib.h>
```

static unsigned long Q[4096], c = 362436;

/* choose random initial c<809430660 and */

/* 4096 random 32-bit integers for Q[]   */

```
unsigned long mwc(void){
```
```
    unsigned long long t, a = 18782LL;
```
```
    static unsigned long i = 4095;
```
```
    unsigned long x, r = 0xfffffffe;
```
```
    i= (i+1)&4095;
```
```
    t = a * Q[i] + c;
```
```
    c=(t >> 32); 
```
```
    x = t + c; 
```
```
    if(x < c)
```
```
    {
```
```
        x++;
```
```
        c++;
```
```
    }
```
```
    return (Q[i] = r - x);   
```
```
}
```
```
int main(void)
```
```
{
```
```
 
```

  printf("\nRandom Number generated : %lld\n", mwc());

```
  return 0;
```
```
}
```

$ gcc mwc.c -o mwc
$ ./mwc
 
Random Number generated: 4294604858

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