Wheel Sieve Method in C

This is a C Program to find prime number between a given range using Wheel Seive method. Wheel factorization is a graphical method for manually performing a preliminary to the Sieve of Eratosthenes that separates prime numbers from composites.

The algorithm goes this way, Start by writing the natural numbers around circles as shown below. Prime numbers in the innermost circle have their multiples in similar positions as themselves in the other circles, forming spokes of primes and their multiples. Multiples of the prime numbers in the innermost circle form spokes of composite numbers in the outer circles.

Here is source code of the C Program to Implement wheel Sieve to Generate Prime Numbers Between Given Range. The C program is successfully compiled and run on a Linux system. The program output is also shown below.

```
#include <stdio.h>
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```
#include <malloc.h>
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```
#define MAX_NUM 50
```

// array will be initialized to 0 being global

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int primes[MAX_NUM];
```
```
 
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void gen_sieve_primes(void) {
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    int p;
```
```
 
```

    // mark all multiples of prime selected above as non primes

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    int c = 2;
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    int mul = p * c;
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    for (p = 2; p < MAX_NUM; p++) // for all elements in array

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    {
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        if (primes[p] == 0) // it is not multiple of any other prime

            primes[p] = 1; // mark it as prime

```
 
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        for (; mul < MAX_NUM;) {
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            primes[mul] = -1;
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            c++;
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            mul = p * c;
```
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        }
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    }
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}
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void print_all_primes() {
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    int c = 0, i;
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    for (i = 0; i < MAX_NUM; i++) {
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        if (primes[i] == 1) {
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            c++;
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```
 
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            if (c < 4) {
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                switch (c) {
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                case 1:
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                    printf("%d st prime is: %d\n", c, i);

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                    break;
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                case 2:
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                    printf("%d nd prime is: %d\n", c, i);

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                    break;
```
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                case 3:
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                    printf("%d rd prime is: %d\n", c, i);

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                    break;
```
```
 
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                default:
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                    break;
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                }
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            }
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```
 
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            else
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                printf("%d th prime is: %d\n", c, i);

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        }
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    }
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}
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```
 
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int main() {
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    gen_sieve_primes();
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    print_all_primes();
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    return 0;
```
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}
```

Output:

$ gcc WheelSeive.c
$ ./a.out
 
1 st prime is: 2
2 nd prime is: 3
3 rd prime is: 5
4 th prime is: 7
5 th prime is: 11
6 th prime is: 13
7 th prime is: 17
8 th prime is: 19
9 th prime is: 23
10 th prime is: 29
11 th prime is: 31
12 th prime is: 37
13 th prime is: 41
14 th prime is: 43
15 th prime is: 47

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