[Easy][Rainbow Table] `input` and `output`'s `type` mismatch

[daehyun99]

Hi there.

leetgpu-challenges/challenges/easy/24_rainbow_table/starter/starter.cu

Lines 1 to 26 in d9fbdf6

	#include <cuda_runtime.h>
	__device__ unsigned int fnv1a_hash(int input) {
	const unsigned int FNV_PRIME = 16777619;
	const unsigned int OFFSET_BASIS = 2166136261;
	unsigned int hash = OFFSET_BASIS;
	for (int byte_pos = 0; byte_pos < 4; byte_pos++) {
	unsigned char byte = (input >> (byte_pos * 8)) & 0xFF;
	hash = (hash ^ byte) * FNV_PRIME;
	}
	return hash;
	}
	__global__ void fnv1a_hash_kernel(const int* input, unsigned int* output, int N, int R) {}
	// input, output are device pointers (i.e. pointers to memory on the GPU)
	extern "C" void solve(const int* input, unsigned int* output, int N, int R) {
	int threadsPerBlock = 256;
	int blocksPerGrid = (N + threadsPerBlock - 1) / threadsPerBlock;
	fnv1a_hash_kernel<<<blocksPerGrid, threadsPerBlock>>>(input, output, N, R);
	cudaDeviceSynchronize();
	}

The input type is int, while the output type is unsigned int.
Since we need to iterate the fnv1a_hash $R$ times, there is a type mismatch.

It would be better to change the input type to unsigned int.

Thanks.

example answer.

#include <cuda_runtime.h>

__device__ unsigned int fnv1a_hash(int input) { // mismatch
    const unsigned int FNV_PRIME = 16777619;
    const unsigned int OFFSET_BASIS = 2166136261;

    unsigned int hash = OFFSET_BASIS;

    for (int byte_pos = 0; byte_pos < 4; byte_pos++) {
        unsigned char byte = (input >> (byte_pos * 8)) & 0xFF;
        hash = (hash ^ byte) * FNV_PRIME;
    }

    return hash;
}

__global__ void fnv1a_hash_kernel(const int* input, unsigned int* output, int N, int R) {
    int idx = blockDim.x * blockIdx.x + threadIdx.x;

    if (idx < N) {
        output[idx] = input[idx]; // mismatch
        for (int i = 0 ; i < R ; ++i) {
            output[idx] = fnv1a_hash(output[idx]); // mismatch
        }
        
    }
}

// input, output are device pointers (i.e. pointers to memory on the GPU)
extern "C" void solve(const int* input, unsigned int* output, int N, int R) {
    int threadsPerBlock = 256;
    int blocksPerGrid = (N + threadsPerBlock - 1) / threadsPerBlock;

    fnv1a_hash_kernel<<<blocksPerGrid, threadsPerBlock>>>(input, output, N, R);
    cudaDeviceSynchronize();
}