1. #include <CL/cl.h>
2. #include <stdio.h>
3. #include <stdlib.h>
4. #include <math.h>
5.  
6. // OpenCL kernel to check if a number is prime
7. const char* kernelSource =
8. "__kernel void is_prime(__global const unsigned long* num, __global int* result) { \n"
9. "    unsigned long n = *num; \n"
10. "    int is_prime = 1; \n"
11. "    for (unsigned long i = 2; i <= sqrt((float)n); i++) { \n"
12. "        if (n % i == 0) { \n"
13. "            is_prime = 0; \n"
14. "            break; \n"
15. "        } \n"
16. "    } \n"
17. "    *result = is_prime; \n"
18. "} \n";
19.  
20. int main() {
21.     // Number to test (example: 31, which is 2^5 - 1)
22.     unsigned long p = 5;
23.     unsigned long M_p = (1UL << p) - 1;
24.  
25.     // Initialize OpenCL
26.     cl_platform_id platform_id = NULL;
27.     cl_device_id device_id = NULL;
28.     cl_context context = NULL;
29.     cl_command_queue command_queue = NULL;
30.     cl_mem num_mem = NULL;
31.     cl_mem result_mem = NULL;
32.     cl_program program = NULL;
33.     cl_kernel kernel = NULL;
34.     cl_int ret;
35.  
36.     // Get platform and device information
37.     ret = clGetPlatformIDs(1, &platform_id, NULL);
38.     ret = clGetDeviceIDs(platform_id, CL_DEVICE_TYPE_DEFAULT, 1, &device_id, NULL);
39.  
40.     // Create an OpenCL context
41.     context = clCreateContext(NULL, 1, &device_id, NULL, NULL, &ret);
42.  
43.     // Create a command queue
44.     command_queue = clCreateCommandQueue(context, device_id, 0, &ret);
45.  
46.     // Create memory buffers on the device for the number and result
47.     num_mem = clCreateBuffer(context, CL_MEM_READ_ONLY, sizeof(unsigned long), NULL, &ret);
48.     result_mem = clCreateBuffer(context, CL_MEM_WRITE_ONLY, sizeof(int), NULL, &ret);
49.  
50.     // Copy the number to the memory buffer
51.     ret = clEnqueueWriteBuffer(command_queue, num_mem, CL_TRUE, 0, sizeof(unsigned long), &M_p, 0, NULL, NULL);
52.  
53.     // Create a program from the kernel source
54.     program = clCreateProgramWithSource(context, 1, (const char**)&kernelSource, NULL, &ret);
55.  
56.     // Build the program
57.     ret = clBuildProgram(program, 1, &device_id, NULL, NULL, NULL);
58.  
59.     // Create the OpenCL kernel
60.     kernel = clCreateKernel(program, "is_prime", &ret);
61.  
62.     // Set the arguments of the kernel
63.     ret = clSetKernelArg(kernel, 0, sizeof(cl_mem), (void*)&num_mem);
64.     ret = clSetKernelArg(kernel, 1, sizeof(cl_mem), (void*)&result_mem);
65.  
66.     // Execute the OpenCL kernel
67.     size_t global_item_size = 1;
68.     size_t local_item_size = 1;
69.     ret = clEnqueueNDRangeKernel(command_queue, kernel, 1, NULL, &global_item_size, &local_item_size, 0, NULL, NULL);
70.  
71.     // Read the result from the device
72.     int result;
73.     ret = clEnqueueReadBuffer(command_queue, result_mem, CL_TRUE, 0, sizeof(int), &result, 0, NULL, NULL);
74.  
75.     // Display the result
76.     if (result) {
77.         printf("%lu is a Mersenne prime.\n", M_p);
78.     } else {
79.         printf("%lu is not a Mersenne prime.\n", M_p);
80.     }
81.  
82.     // Clean up
83.     ret = clFlush(command_queue);
84.     ret = clFinish(command_queue);
85.     ret = clReleaseKernel(kernel);
86.     ret = clReleaseProgram(program);
87.     ret = clReleaseMemObject(num_mem);
88.     ret = clReleaseMemObject(result_mem);
89.     ret = clReleaseCommandQueue(command_queue);
90.     ret = clReleaseContext(context);
91.  
92.     return 0;
93. }