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radix_cuda.cpp

#include <iostream>
#include <cuda.h>
#include <algorithm>
#include <cstdlib>

#define MAX_SIZE 10

__global__ void radix_sort_kernel(int* A, int n)
{
	// Find the maximum value
	int max_val = 0;
	for (int i = 0; i < n; i++)
		max_val = max(max_val, A[i]);

	// Find the number of digits in the maximum value
	int digits = 0;
	while (max_val > 0)
	{
		digits++;
		max_val /= 10;
	}

	// Create an array to store counts for each digit
	int counts[10];
	for (int i = 0; i < 10; i++)
		counts[i] = 0;

	// Count the number of occurrences of each digit
	for (int i = 0; i < n; i++)
	{
		int digit = A[i] % 10;
		counts[digit]++;
	}

	// Calculate the starting index for each digit
	int start[10];
	start[0] = 0;
	for (int i = 1; i < 10; i++)
		start[i] = start[i-1] + counts[i-1];

	// Create an array to store the sorted list
	int B[n];

	// Sort the elements
	for (int d = 0; d < digits; d++)
	{
		// Copy the elements into the temp array
		for (int i = 0; i < n; i++)
		{
			int digit = (A[i] / (int)pow(10, d)) % 10;
			int index = start[digit]++;
			B[index] = A[i];
		}

		// Copy the elements back into the original array
		for (int i = 0; i < n; i++)
			A[i] = B[i];
	}
}

int main()
{
    int arr[MAX_SIZE];
    int *dev_arr;
    
    // Fill array with random values
    for(int i = 0; i < MAX_SIZE; i++)
    	arr[i] = rand() % 100;
    
    // Allocate memory on the device
    cudaMalloc((void**)&dev_arr, MAX_SIZE * sizeof(int));
    
    // Copy array to the device
    cudaMemcpy(dev_arr, arr, MAX_SIZE * sizeof(int), cudaMemcpyHostToDevice);
    
    // Run the kernel
    radix_sort_kernel<<<1, MAX_SIZE>>>(dev_arr, MAX_SIZE);
    
    // Copy the results back to the host
    cudaMemcpy(arr, dev_arr, MAX_SIZE * sizeof(int), cudaMemcpyDeviceToHost);
    
    // Print the results
    for (int i = 0; i < MAX_SIZE; i++)
    	std::cout << arr[i] << " ";
    	
    std::cout << std::endl;
    
    // Free device memory
    cudaFree(dev_arr);
    
    return 0;
}