=== Assignment 3 ===
The kernel code we used to optimize our code
<syntaxhighlight lang="cpp">
#include <stdlib.h>
#include <stdio.h>
#include <cuda.h>
#include <math.h>
#include <time.h>
#include <curand_kernel.h>
#include <cstdlib>
#define BLOCKS 30
#define THREADS 8
#define PI 3.1415926535 // known value of pi
__global__ void gpu_monte_carlo(float *estimate, curandState *states, float n) {
estimate[tid] = 4.0f * points_in_circle / n; // return estimate of pi
}
</syntaxhighlight>
float host_monte_carlo(long trials) { float x, y; long points_in_circle = 0; for (long i = 0; i < trials; i++) { x = rand() / (float)RAND_MAX; y = rand() / (float)RAND_MAX; points_in_circle += (x*x + y*y <= 1.0f); } return 4.0f * points_in_circle / trials;} int main(int argc, char** argv) { clock_t start, stop; curandState *devStates; float n = std'''Test runs::atoi(argv[1]); dim3 dimGrid(BLOCKS, 1, 1); // Grid dimensions dim3 dimBlock(THREADS, 1, 1); // Block dimensions float *dev, *host; size_t size = BLOCKS * THREADS* sizeof(float); //Array memory size printf("# of trials per thread = %.0f, # of blocks = %d, # of threads/block = %d.\n", n, BLOCKS, THREADS); start = clock(); host = (float *)malloc(size); // Allocate array on host cudaMalloc((void **)&dev, size); // Allocate array on device cudaMemset(dev, 0, size); cudaMalloc((void **)&devStates, THREADS * BLOCKS * sizeof(curandState)); gpu_monte_carlo << <BLOCKS, THREADS >> >(dev, devStates, n); cudaMemcpy(host, dev, size, cudaMemcpyDeviceToHost); // return results float pi_gpu = 0.0f; for (int i = 0; i < BLOCKS * THREADS; i++) { pi_gpu += host[i]; } pi_gpu /= (BLOCKS * THREADS); stop = clock(); printf("GPU pi calculated in %f s.\n", (stop - start) / (float)CLOCKS_PER_SEC); start = clock(); //float pi_cpu = host_monte_carlo(BLOCKS * THREADS * n); stop = clock(); printf("CPU pi calculated in %f s.\n", (stop - start) / (float)CLOCKS_PER_SEC); printf("CUDA estimate of PI = %f [error of %f]\n", pi_gpu, pi_gpu - PI); //printf("CPU estimate of PI = %f [error of %f]\n", pi_cpu, pi_cpu - PI);
return 0;
}
</syntaxhighlight>
How we optimize and improved the code is instead of using a randomized number we ask the user for input on pi calculation.