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mandelbrot.cpp
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mandelbrot.cpp
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#include <math.h>
#include <pthread.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/sysinfo.h>
#include <time.h>
#define STB_IMAGE_WRITE_IMPLEMENTATION 1
// #include "matplotlib_colormaps.h"
#include "scm_colormaps.h"
#include "stb_image_write.h"
uint32_t max_steps = 1 << 11;
uint32_t min_steps = 1 << 7;
#define COUNT(a) (sizeof(a) / sizeof(0 [a]))
#define LERP(a, b, u) ((a) * (1 - (u)) + (b) * (u))
union BufferData {
uint32_t value;
struct {
uint8_t r, g, b, a;
};
};
static inline long double rand_range(long double min, long double max) {
long double u = (long double)rand() / RAND_MAX;
return LERP(min, max, u);
}
static uint32_t mandelbrot(long double x, long double y) {
long double r = x;
long double i = y;
long double mag_sq = r * r + i * i;
uint32_t steps = 0;
while (steps < max_steps && mag_sq <= 4) {
long double rr = r * r - i * i + x;
i = 2 * r * i + y;
r = rr;
mag_sq = r * r + i * i;
steps++;
}
return steps;
}
static uint32_t choose_center(long double& x, long double& y) {
uint32_t steps;
do {
x = rand_range(-1.5, 1);
y = rand_range(0, 1);
steps = mandelbrot(x, y);
} while (steps < min_steps || steps >= max_steps);
return steps;
}
struct CalcBufferData {
int thread_id;
BufferData* buffer;
int start_line, last_line;
int width, height;
uint32_t smin, smax;
long double xmin, xmax, ymin, ymax;
};
static void* calc_buffer(void* p) {
CalcBufferData* data = (CalcBufferData*)p;
BufferData* b = data->buffer + data->start_line * data->width;
#ifdef DEBUG
printf("Thread %d: filling from %d to %d.\n", data->thread_id, data->start_line,
data->last_line - 1);
fflush(stdout);
#endif
for (int j = data->start_line; j < data->last_line; j++) {
const long double v = (long double)j / (data->height - 1.0);
const long double y = LERP(data->ymin, data->ymax, v);
for (int i = 0; i < data->width; i++, b++) {
const long double u = (long double)i / (data->width - 1.0);
const long double x = LERP(data->xmin, data->xmax, u);
const uint32_t steps = 1 + mandelbrot(x, y); // Add 1 due to log scaling
b->value = steps;
if (steps < data->smin) {
data->smin = steps;
} else if (steps > data->smax) {
data->smax = steps;
}
}
}
#ifdef DEBUG
printf("Thread %d: done.\n", data->thread_id);
fflush(stdout);
#endif
return NULL;
}
struct GenImageData {
int thread_id;
BufferData* buffer;
int start_line, last_line;
int width, height;
long double log_min, log_delta;
uint8_t* colormap;
int max_index;
};
static void* gen_image(void* p) {
GenImageData* data = (GenImageData*)p;
BufferData* b = data->buffer + data->start_line * data->width;
#ifdef DEBUG
printf("Thread %d: generating image from %d to %d.\n", data->thread_id, data->start_line,
data->last_line - 1);
fflush(stdout);
#endif
for (int j = data->start_line; j < data->last_line; j++) {
for (int i = 0; i < data->width; i++, b++) {
long double value = (log(b->value) - data->log_min) / data->log_delta;
if (value < 0)
value = 0;
else if (value > 1)
value = 1;
const int index = int(0.5 + value * data->max_index);
const uint8_t* sample = data->colormap + 3 * index;
b->r = *sample++;
b->g = *sample++;
b->b = *sample++;
b->a = 0xFF;
}
}
#ifdef DEBUG
printf("Thread %d: done.\n", data->thread_id);
fflush(stdout);
#endif
return NULL;
}
int main(int argc, char* argv[]) {
const uint8_t* colormaps[] = {acton, bamako, batlow, berlin, bilbao, broc, broco,
buda, cork, corko, davos, devon, grayc, hawaii,
imola, lajolla, lapaz, lisbon, nuuk, oleron, oslo,
roma, romao, tofino, tokyo, turku, vik, viko};
const int colormap_sizes[] = {
COUNT(acton), COUNT(bamako), COUNT(batlow), COUNT(berlin), COUNT(bilbao), COUNT(broc),
COUNT(broco), COUNT(buda), COUNT(cork), COUNT(corko), COUNT(davos), COUNT(devon),
COUNT(grayc), COUNT(hawaii), COUNT(imola), COUNT(lajolla), COUNT(lapaz), COUNT(lisbon),
COUNT(nuuk), COUNT(oleron), COUNT(oslo), COUNT(roma), COUNT(romao), COUNT(tofino),
COUNT(tokyo), COUNT(turku), COUNT(vik), COUNT(viko)};
const char* colormap_names[] = {"acton", "bamako", "batlow", "berlin", "bilbao", "broc",
"broco", "buda", "cork", "corko", "davos", "devon",
"grayc", "hawaii", "imola", "lajolla", "lapaz", "lisbon",
"nuuk", "oleron", "oslo", "roma", "romao", "tofino",
"tokyo", "turku", "vik", "viko"};
const char* filename = NULL;
int wid = 960;
int hei = 540;
bool center_set = false;
bool size_set = false;
long double x = 0;
long double y = 0;
long double dx = 0;
long double dy = 0;
int cmap_choice = -1;
unsigned int seed = time(NULL);
int num_threads = get_nprocs() - 1;
if (num_threads <= 0) num_threads = 1;
for (int i = 1; i < argc; i++) {
#ifdef DEBUG
printf("Parsing argument %s\n", argv[i]);
#endif
if (argv[i][0] != '-') {
filename = argv[i];
#ifdef DEBUG
printf("Output filename: %s\n", filename);
#endif
continue;
}
switch (argv[i][1]) {
case 'h':
printf(
"Usage: %s [OPTION]... FILENAME\n\n"
"Options:\n"
" -h Show this help message and exit.\n"
" -g WIDTH HEIGHT Image size (defaults %d %d).\n"
" -c X Y View window center.\n"
" -s DX DY View window size.\n"
" -z MIN MAX Minimal value to accept a random "
"coordinate as image\n"
" center and maximal value for the "
"fractal calculation\n"
" (defaults %u %u).\n"
" -m COLORMAP Colormap name. Available "
"options:\n",
argv[0], wid, hei, min_steps, max_steps);
for (int i = 0; i < COUNT(colormap_names);) {
int remaining = 54;
printf(" ");
while (i < COUNT(colormaps) && remaining >= 2 + strlen(colormap_names[i])) {
remaining -= 2 + strlen(colormap_names[i]);
printf(" %s", colormap_names[i++]);
if (i < COUNT(colormaps)) putchar(',');
}
putchar('\n');
}
printf(
" -r RNG_SEED Random number generator seed.\n"
" -p NUM Number of threads to use (default %d).\n",
num_threads);
return 0;
break;
case 'g':
if (++i == argc) {
fprintf(stderr, "Error: missing value after option %s.\n", argv[i - 1]);
return 1;
}
wid = atoi(argv[i]);
if (++i == argc) {
fprintf(stderr, "Error: missing value after option %s.\n", argv[i - 2]);
return 1;
}
hei = atoi(argv[i]);
if (wid <= 0 || hei <= 0) {
fprintf(stderr, "Width (%d) and height (%d) must be greater than 0.\n", wid,
hei);
return 1;
}
break;
case 'c':
if (++i == argc) {
fprintf(stderr, "Error: missing value after option %s.\n", argv[i - 1]);
return 1;
}
x = strtold(argv[i], NULL);
if (++i == argc) {
fprintf(stderr, "Error: missing value after option %s.\n", argv[i - 2]);
return 1;
}
y = strtold(argv[i], NULL);
center_set = true;
break;
case 's':
if (++i == argc) {
fprintf(stderr, "Error: missing value after option %s.\n", argv[i - 1]);
return 1;
}
dx = strtold(argv[i], NULL) / 2;
if (++i == argc) {
fprintf(stderr, "Error: missing value after option %s.\n", argv[i - 2]);
return 1;
}
dy = strtold(argv[i], NULL) / 2;
size_set = true;
break;
case 'z':
if (++i == argc) {
fprintf(stderr, "Error: missing value after option %s.\n", argv[i - 1]);
return 1;
}
min_steps = strtoul(argv[i], NULL, 0);
if (++i == argc) {
fprintf(stderr, "Error: missing value after option %s.\n", argv[i - 2]);
return 1;
}
max_steps = strtoul(argv[i], NULL, 0);
if (min_steps >= max_steps) {
fprintf(stderr, "MIN (%u) must be greater than MAX (%u).\n", min_steps,
max_steps);
return 1;
}
break;
case 'm':
if (++i == argc) {
fprintf(stderr, "Error: missing value after option %s.\n", argv[i - 1]);
return 1;
}
for (int j = 0; j < COUNT(colormaps); j++) {
if (strcmp(argv[i], colormap_names[j]) == 0) {
cmap_choice = j;
break;
}
}
if (cmap_choice < 0) {
fprintf(stderr,
"Error: invalid colormap choice %s. Try -h for "
"help.\n",
argv[i]);
return 1;
}
break;
case 'r':
if (++i == argc) {
fprintf(stderr, "Error: missing value after option %s.\n", argv[i - 1]);
return 1;
}
seed = strtoul(argv[i], NULL, 0);
break;
case 'p':
if (++i == argc) {
fprintf(stderr, "Error: missing value after option %s.\n", argv[i - 1]);
return 1;
}
num_threads = atoi(argv[i]);
if (num_threads <= 0) {
fprintf(stderr,
"Error: invalid value for number of threads (%s == "
"%d).\n",
argv[i], num_threads);
return 1;
}
break;
default:
fprintf(stderr, "Error: unexpected parameter %s.\n", argv[i]);
return 1;
}
}
if (filename == NULL) {
fprintf(stderr, "Error: missing filename!\nUsage: %s [OPTIONS] FILENAME\n", argv[0]);
return 1;
}
#ifdef DEBUG
printf("Seed: %u\nRunning with %d threads.\nImage size: %d x %d\n", seed, num_threads, wid,
hei);
#endif
srand(seed);
uint32_t steps;
if (center_set)
steps = mandelbrot(x, y);
else
steps = choose_center(x, y);
if (!size_set) {
dx = powl(steps, rand_range(-2.5, -1));
dy = dx * hei / wid;
}
#ifdef DEBUG
printf("Image window: (%Lg, %Lg) x (%Lg, %Lg).\n", x - dx, y - dy, x + dx, y + dy);
#endif
if (cmap_choice < 0) cmap_choice = rand() % COUNT(colormaps);
#ifdef DEBUG
printf("Using colormap %d.\n", cmap_choice);
#endif
uint8_t* colormap = (uint8_t*)colormaps[cmap_choice];
const int max_index = colormap_sizes[cmap_choice] / 3 - 1;
BufferData* buffer = (BufferData*)malloc(sizeof(BufferData) * wid * hei);
const int lines_per_thread = hei / num_threads + 1;
const int pitch = lines_per_thread * wid;
pthread_t thread[num_threads];
CalcBufferData cb_data[num_threads];
for (int t = 0; t < num_threads; t++) {
cb_data[t] = {t,
buffer,
t * lines_per_thread,
(t == num_threads - 1) ? hei : (t + 1) * lines_per_thread,
wid,
hei,
max_steps + 1,
0,
x - dx,
x + dx,
y - dy,
y + dy};
pthread_create(thread + t, NULL, calc_buffer, (void*)(cb_data + t));
}
uint32_t smin = max_steps + 1;
uint32_t smax = 0;
for (int t = 0; t < num_threads; t++) {
pthread_join(thread[t], NULL);
#ifdef DEBUG
printf("Joined thread %d.\n", t);
fflush(stdout);
#endif
if (cb_data[t].smin < smin) smin = cb_data[t].smin;
if (cb_data[t].smax > smax) smax = cb_data[t].smax;
}
const long double log_min = log(smin);
const long double log_max = log(smax);
long double log_delta;
if (log_max > log_min) {
log_delta = log_max - log_min;
} else {
log_delta = 1.0;
printf("WARNING: Selected window contains no detectable variation.\n");
fflush(stdout);
}
GenImageData gi_data[num_threads];
for (int t = 0; t < num_threads; t++) {
gi_data[t] = {t,
buffer,
t * lines_per_thread,
(t == num_threads - 1) ? hei : (t + 1) * lines_per_thread,
wid,
hei,
log_min,
log_delta,
colormap,
max_index};
pthread_create(thread + t, NULL, gen_image, (void*)(gi_data + t));
}
for (int t = 0; t < num_threads; t++) {
pthread_join(thread[t], NULL);
#ifdef DEBUG
printf("Joined thread %d.\n", t);
fflush(stdout);
#endif
}
#ifdef DEBUG
printf("Saving image.\n");
fflush(stdout);
#endif
stbi_write_png_compression_level = 10;
stbi_write_png(filename, wid, hei, 4, buffer, wid * 4);
#ifdef DEBUG
printf("Done.\n");
fflush(stdout);
#endif
free(buffer);
return 0;
}