add one-threaded C example

This commit is contained in:
NunoSempere 2023-05-29 19:55:57 -04:00
parent 160e824108
commit 03421f953b
3 changed files with 189 additions and 7 deletions

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@ -12,6 +12,9 @@ CC=gcc
SRC=samples.c SRC=samples.c
OUTPUT=out/samples OUTPUT=out/samples
SRC_ONE_THREAD=./samples-one-thread.c
OUTPUT_ONE_THREAD=out/samples-one-thread
## Dependencies ## Dependencies
# Has no dependencies # Has no dependencies
MATH=-lm MATH=-lm
@ -30,24 +33,20 @@ FORMATTER=clang-format -i -style=$(STYLE_BLUEPRINT)
## make build ## make build
build: $(SRC) build: $(SRC)
$(CC) $(OPTIMIZED) $(DEBUG) $(SRC) $(OPENMP) $(MATH) -o $(OUTPUT) $(CC) $(OPTIMIZED) $(DEBUG) $(SRC) $(OPENMP) $(MATH) -o $(OUTPUT)
$(CC) $(OPTIMIZED) $(DEBUG) $(SRC_ONE_THREAD) $(OPENMP) $(MATH) -o $(OUTPUT_ONE_THREAD)
#fast: Has been removed, compilation of "build" is very fast and it outputs optimized code by default
format: $(SRC) format: $(SRC)
$(FORMATTER) $(SRC) $(FORMATTER) $(SRC)
run: $(SRC) $(OUTPUT) run: $(SRC) $(OUTPUT)
OMP_NUM_THREADS=1 ./$(OUTPUT) OMP_NUM_THREADS=1 ./$(OUTPUT)
./$(OUTPUT_ONE_THREAD)
multi: $(SRC) $(OUTPUT)
OMP_NUM_THREADS=1 ./$(OUTPUT) && echo
OMP_NUM_THREADS=2 ./$(OUTPUT) && echo
OMP_NUM_THREADS=4 ./$(OUTPUT)
time: time:
OMP_NUM_THREADS=1 /bin/time -f "Time: %es" ./$(OUTPUT) && echo OMP_NUM_THREADS=1 /bin/time -f "Time: %es" ./$(OUTPUT) && echo
OMP_NUM_THREADS=2 /bin/time -f "Time: %es" ./$(OUTPUT) && echo OMP_NUM_THREADS=2 /bin/time -f "Time: %es" ./$(OUTPUT) && echo
OMP_NUM_THREADS=4 /bin/time -f "Time: %es" ./$(OUTPUT) && echo OMP_NUM_THREADS=4 /bin/time -f "Time: %es" ./$(OUTPUT) && echo
/bin/time -f "Time: %es" ./$(OUTPUT_ONE_THREAD) && echo
linux-install: linux-install:
sudo apt-get install libomp-dev sudo apt-get install libomp-dev

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@ -0,0 +1,183 @@
#include <math.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;
{
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)
{
return ((float)rand() / (float)RAND_MAX) * to;
}
float ur_normal()
{
float u1 = rand_float(1.0);
float u2 = rand_float(1.0);
float z = sqrtf(-2.0 * log(u1)) * sin(2 * PI * u2);
return z;
}
inline float random_uniform(float from, float to)
{
return ((float)rand() / (float)RAND_MAX) * (to - from) + from;
}
inline float random_normal(float mean, float sigma)
{
return (mean + sigma * ur_normal());
}
inline float random_lognormal(float logmean, float logsigma)
{
return expf(random_normal(logmean, logsigma));
}
inline float random_to(float low, float high)
{
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);
}
void array_random_to(float* array, int length, float low, float high)
{
int i;
#pragma omp private(i)
{
#pragma omp for
for (i = 0; i < length; i++) {
array[i] = random_to(low, high);
}
}
}
void mixture(float (*samplers[])(void), float* weights, int n_dists, float* results, int results_length)
{
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;
{
for (int i = 0; i < results_length; i++) {
p1 = random_uniform(0, 1);
for (int j = 0; j < n_dists; j++) {
if (p1 < cummulative_weights[j]) {
results[i] = samplers[j]();
break;
}
}
}
}
free(normalized_weights);
free(cummulative_weights);
}
float sample_0()
{
return 0;
}
float sample_1()
{
return 1;
}
float sample_few()
{
return random_to(1, 3);
}
float sample_many()
{
return random_to(2, 10);
}
int main()
{
//initialize randomness
srand(1);
// clock_t start, end;
// start = clock();
// Toy example
// Declare variables in play
float p_a, p_b, p_c;
// printf("Max threads: %d\n", n_threads);
// omp_set_num_threads(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[])(void) = { sample_0, sample_1, sample_few, sample_many };
float* results = malloc(N * sizeof(float));
mixture(samplers, weights, n_dists, results, N);
printf("Sum(dist_mixture, N)/N = %f\n", array_sum(results, N) / N);
// array_print(dist_mixture[0], N);
// end = clock();
// printf("Time (ms): %f\n", ((double)(end - start)) / (CLOCKS_PER_SEC * 10) * 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;
}