time-to-botec/C-optimized/samples.c
2023-06-02 13:17:12 -06:00

282 lines
8.1 KiB
C

#include <math.h>
#include <omp.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
const float PI = 3.14159265358979323846;
#define N 1000000
//Array helpers
void array_print(float* array, int length)
{
for (int i = 0; i < length; i++) {
printf("item[%d] = %f\n", i, array[i]);
}
printf("\n");
}
void array_fill(float* array, int length, float item)
{
int i;
#pragma omp private(i)
{
#pragma omp for
for (i = 0; i < length; i++) {
array[i] = item;
}
}
}
float array_sum(float* array, int length)
{
float output = 0.0;
for (int i = 0; i < length; i++) {
output += array[i];
}
return output;
}
void array_cumsum(float* array_to_sum, float* array_cumsummed, int length)
{
array_cumsummed[0] = array_to_sum[0];
for (int i = 1; i < length; i++) {
array_cumsummed[i] = array_cumsummed[i - 1] + array_to_sum[i];
}
}
float rand_float(float to, unsigned int* seed)
{
return ((float)rand_r(seed) / (float)RAND_MAX) * to;
// See: <https://stackoverflow.com/questions/43151361/how-to-create-thread-safe-random-number-generator-in-c-using-rand-r>
// rand() is not thread-safe, as it relies on (shared) hidden state.
}
float ur_normal(unsigned int* seed)
{
float u1 = rand_float(1.0, seed);
float u2 = rand_float(1.0, seed);
float z = sqrtf(-2.0 * log(u1)) * sin(2 * PI * u2);
return z;
}
inline float random_uniform(float from, float to, unsigned int* seed)
{
return ((float) rand_r(seed) / (float)RAND_MAX) * (to - from) + from;
}
inline float random_normal(float mean, float sigma, unsigned int* seed)
{
return (mean + sigma * ur_normal(seed));
}
inline float random_lognormal(float logmean, float logsigma, unsigned int* seed)
{
return expf(random_normal(logmean, logsigma, seed));
}
inline float random_to(float low, float high, unsigned int* seed)
{
const float NORMAL95CONFIDENCE = 1.6448536269514722;
float loglow = logf(low);
float loghigh = logf(high);
float logmean = (loglow + loghigh) / 2;
float logsigma = (loghigh - loglow) / (2.0 * NORMAL95CONFIDENCE);
return random_lognormal(logmean, logsigma, seed);
}
int split_array_get_my_length(int index, int total_length, int n_threads)
{
return (total_length % n_threads > index ? total_length / n_threads + 1 : total_length / n_threads);
}
//Old version, don't use it!! Optimized version is called mixture_f. This one is just for display
/*
void mixture(float* dists[], float* weights, int n_dists, float* results)
{
float sum_weights = array_sum(weights, n_dists);
float* normalized_weights = malloc(n_dists * sizeof(float));
for (int i = 0; i < n_dists; i++) {
normalized_weights[i] = weights[i] / sum_weights;
}
float* cummulative_weights = malloc(n_dists * sizeof(float));
array_cumsum(normalized_weights, cummulative_weights, n_dists);
//create var holders
float p1, p2;
int index_found, index_counter, sample_index, i;
#pragma omp parallel private(i, p1, p2, index_found, index_counter, sample_index)
{
#pragma omp for
for (i = 0; i < N; i++) {
p1 = random_uniform(0, 1);
p2 = random_uniform(0, 1);
index_found = 0;
index_counter = 0;
while ((index_found == 0) && (index_counter < n_dists)) {
if (p1 < cummulative_weights[index_counter]) {
index_found = 1;
} else {
index_counter++;
}
}
if (index_found != 0) {
sample_index = (int)(p2 * N);
results[i] = dists[index_counter][sample_index];
} else
printf("This shouldn't be able to happen.\n");
}
}
free(normalized_weights);
free(cummulative_weights);
}
*/
void mixture_f(float (*samplers[])(unsigned int* ), float* weights, int n_dists, float** results, int n_threads)
{
float sum_weights = array_sum(weights, n_dists);
float* normalized_weights = malloc(n_dists * sizeof(float));
for (int i = 0; i < n_dists; i++) {
normalized_weights[i] = weights[i] / sum_weights;
}
float* cummulative_weights = malloc(n_dists * sizeof(float));
array_cumsum(normalized_weights, cummulative_weights, n_dists);
//create var holders
float p1;
int sample_index, i, own_length;
unsigned int* seeds[n_threads];
for(unsigned int i=0; i<n_threads; i++){
seeds[i] = malloc(sizeof(unsigned int));
*seeds[i] = i;
}
#pragma omp parallel private(i, p1, sample_index, own_length)
{
#pragma omp for
for (i = 0; i < n_threads; i++) {
own_length = split_array_get_my_length(i, N, n_threads);
for (int j = 0; j < own_length; j++) {
p1 = random_uniform(0, 1, seeds[i]);
for (int k = 0; k < n_dists; k++) {
if (p1 < cummulative_weights[k]) {
results[i][j] = samplers[k](seeds[i]);
break;
}
}
}
}
}
free(normalized_weights);
free(cummulative_weights);
for(unsigned int i=0; i<n_threads; i++){
free(seeds[i]);
}
}
float sample_0(unsigned int* seed)
{
return 0;
}
float sample_1(unsigned int* seed)
{
return 1;
}
float sample_few(unsigned int* seed)
{
return random_to(1, 3, seed);
}
float sample_many(unsigned int* seed)
{
return random_to(2, 10, seed);
}
void split_array_allocate(float** meta_array, int length, int divide_into)
{
int own_length;
for (int i = 0; i < divide_into; i++) {
own_length = split_array_get_my_length(i, length, divide_into);
meta_array[i] = malloc(own_length * sizeof(float));
}
}
void split_array_free(float** meta_array, int divided_into)
{
for (int i = 0; i < divided_into; i++) {
free(meta_array[i]);
}
free(meta_array);
}
float split_array_sum(float** meta_array, int length, int divided_into)
{
int i;
float output;
float* partial_sum = malloc(divided_into * sizeof(float));
#pragma omp private(i) shared(partial_sum)
for (int i = 0; i < divided_into; i++) {
float own_partial_sum = 0;
int own_length = split_array_get_my_length(i, length, divided_into);
for (int j = 0; j < own_length; j++) {
own_partial_sum += meta_array[i][j];
}
partial_sum[i] = own_partial_sum;
}
for (int i = 0; i < divided_into; i++) {
output += partial_sum[i];
}
return output;
}
int main()
{
//initialize randomness
srand(time(NULL));
// clock_t start, end;
// start = clock();
// Toy example
// Declare variables in play
float p_a, p_b, p_c;
int n_threads = omp_get_max_threads();
// printf("Max threads: %d\n", n_threads);
// omp_set_num_threads(n_threads);
float** dist_mixture = malloc(n_threads * sizeof(float*));
split_array_allocate(dist_mixture, N, n_threads);
// Initialize variables
p_a = 0.8;
p_b = 0.5;
p_c = p_a * p_b;
// Generate mixture
int n_dists = 4;
float weights[] = { 1 - p_c, p_c / 2, p_c / 4, p_c / 4 };
float (*samplers[])(unsigned int* ) = { sample_0, sample_1, sample_few, sample_many };
mixture_f(samplers, weights, n_dists, dist_mixture, n_threads);
printf("Sum(dist_mixture, N)/N = %f\n", split_array_sum(dist_mixture, N, n_threads) / N);
// array_print(dist_mixture[0], N);
split_array_free(dist_mixture, n_threads);
// end = clock();
// printf("Time (ms): %f\n", ((double)(end - start)) / (CLOCKS_PER_SEC) * 1000);
// ^ Will only measure how long it takes the inner main to run, not the whole program,
// including e.g., loading the program into memory or smth.
// Also CLOCKS_PER_SEC in POSIX is a constant equal to 1000000.
// See: https://stackoverflow.com/questions/10455905/why-is-clocks-per-sec-not-the-actual-number-of-clocks-per-second
return 0;
}