1 files changed, 69 insertions, 0 deletions
diff --git a/hashstrings.cu b/hashstrings.cu
new file mode 100644
index 0000000..6c72170
--- /dev/null
+++ b/hashstrings.cu
@@ -0,0 +1,69 @@
+#include <stdio.h>
+#include <math.h>
+
+#define STRING_LENGTH 4
+
+const int n = 26;
+const int num_elements = pow(n, STRING_LENGTH);
+const int threads_per_block = 256;
+
+__device__ long compute_hash_code(const char* str, int n)
+{
+	long result = 0;
+	for (int i = 0; i < n; i++)
+		result = 31 * result + str[i];
+	return result;
+}
+
+__global__ void find_from_generated_strings(long* hash_to_find, char* result_str,
+		int total_elements)
+{
+	char str[STRING_LENGTH + 1];
+
+	int i = threadIdx.x + blockIdx.x * blockDim.x;
+	if (i >= total_elements)
+		return;
+
+	for (int j = 0; j < STRING_LENGTH; j++) {
+		int string_index = STRING_LENGTH - (j + 1);
+		int char_index = (i / (int)pow(n, j)) % n;
+		str[string_index] = 'a' + char_index;
+	}
+
+	if (compute_hash_code(str, STRING_LENGTH) == *hash_to_find) {
+		memcpy(result_str, str, STRING_LENGTH);
+		return;
+	}
+}
+
+int main()
+{
+	long hash_to_find = 3446974;
+	char result[STRING_LENGTH + 1];
+
+	long* to_find_on_device;
+	char* result_string_on_device;
+
+	cudaMalloc(&to_find_on_device, sizeof(long));
+	cudaMalloc(&result_string_on_device, STRING_LENGTH + 1);
+
+	cudaMemcpy(to_find_on_device, &hash_to_find, sizeof(int),
+			cudaMemcpyHostToDevice);
+
+	const int num_blocks = (num_elements + threads_per_block - 1) /
+		threads_per_block;
+	printf("We have %d items to compute\n", num_elements);
+	printf("Running with %d blocks and %d threads per block\n", num_blocks,
+			threads_per_block);
+	find_from_generated_strings<<<num_blocks, threads_per_block>>>(to_find_on_device,
+			result_string_on_device, num_elements);
+
+	cudaMemcpy(result, result_string_on_device, STRING_LENGTH + 1, cudaMemcpyDeviceToHost);
+
+	printf("%s\n", result);
+
+	cudaFree(to_find_on_device);
+	cudaFree(result_string_on_device);
+
+	return 0;
+}