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→Assignment 3
=== Assignment 3 ===
The code we used to optimize our code
<codeblock>
#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) {
unsigned int tid = threadIdx.x + blockDim.x * blockIdx.x;
float points_in_circle = 0;
float x, y;
curand_init(1234, tid, 0, &states[tid]); // Initialize CURAND
for (int i = 0; i < n; i++) {
x = curand_uniform(&states[tid]);
y = curand_uniform(&states[tid]);
points_in_circle += (x*x + y*y <= 1.0f); // count if x & y is in the circle.
}
estimate[tid] = 4.0f * points_in_circle / n; // return estimate of pi
}
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::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;
}
</codeblock>
How we optimize and improved the code is instead of using a randomized number we ask the user for input on pi calculation.
