'''1. Introduction'''
* Maze
The program generates a maze in png file. It takes 2 arguments: the height and the width of the maze.
*Original Code:
/*
* MazePng.cpp
*
* Created on: 12 Jul 2013
* Author: yac
*/
#include "MazePng.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
const png_byte WALL = 0x00;
const png_byte PATH = 0xFF;
MazePng::MazePng(const unsigned int width, const unsigned int height) :
AbstractMaze(width, height) {
}
MazePng::~MazePng() { }
void MazePng::toPng(unsigned int scale) {
png_byte color_type;
png_byte bit_depth;
png_structp png_ptr;
png_infop info_ptr;
png_bytep *row_pointers;
int height, width;
FILE *fp;
width = (this->width * 2) + 1;
height = (this->height * 2) + 1;
color_type = PNG_COLOR_TYPE_RGB;
bit_depth = 8;
row_pointers = new png_bytep[height];
for (int i = 0; i < height; ++i) {
row_pointers[i] = new png_byte[width * 3];
for (int j = 0; j < width * 3; j += 3) {
row_pointers[i][j] = WALL;
row_pointers[i][j + 1] = WALL;
row_pointers[i][j + 2] = WALL;
}
}
createImage(row_pointers, 0);
fp = fopen("out.png", "wb");
png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
info_ptr = png_create_info_struct(png_ptr);
png_init_io(png_ptr, fp);
png_set_IHDR(png_ptr, info_ptr, width, height, bit_depth, color_type,
PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE,
PNG_FILTER_TYPE_BASE);
png_write_info(png_ptr, info_ptr);
png_write_image(png_ptr, row_pointers);
png_write_end(png_ptr, NULL);
png_destroy_write_struct(&png_ptr, &info_ptr);
for (int i = 0; i < height; ++i) {
delete[] row_pointers[i];
}
delete[] row_pointers;
fclose(fp);
}
void inline MazePng::setPixel(png_bytep *row_pointers, unsigned int x, unsigned int y,
png_byte type) {
row_pointers[y][0 + 3 * x] = type;
row_pointers[y][1 + 3 * x] = type;
row_pointers[y][2 + 3 * x] = type;
}
void MazePng::createImage(png_bytep *row_pointers, unsigned int scale) {
/*
for (unsigned int x = 0; x < ((width * 2) + 1); ++x) {
setPixel(row_pointers, x, 0, WALL);
}
*/
if (start < width) {
setPixel(row_pointers, start * 2 + 1, 0, PATH);
}
png_byte temp[2] = { 0 };
for (unsigned int y = 0; y < height; ++y) {
setPixel(row_pointers, 0, (y * 2) + 1, WALL);
for (unsigned int x = 0; x < width; ++x) {
switch ((cells[(y * width) + x] & 0xC0) >> 6) {
case 2:
temp[0] = PATH;
setPixel(row_pointers, 2 + (x * 2), (y * 2) + 1, temp[0]);
break;
case 1:
temp[1] = PATH;
setPixel(row_pointers, 1 + (x * 2), (y * 2) + 2, temp[1]);
break;
case 0:
setPixel(row_pointers, 2 + (x * 2), (y * 2) + 1, temp[0]);
setPixel(row_pointers, 1 + (x * 2), (y * 2) + 2, temp[1]);
break;
}
setPixel(row_pointers, 1 + (x * 2), (y * 2) + 1, PATH);
}
}
}
* Analysis:
'''Parallelizable?'''
The program function named toPng() has a runtime of O(n^2); it takes up an average of 42% (min: 35%; max: 50%) of the program's execution time.
for (int i = 0; i < height; ++i) {
row_pointers[i] = new png_byte[width * 3];
for (int j = 0; j < width * 3; j += 3) {
row_pointers[i][j] = WALL;
row_pointers[i][j + 1] = WALL;
row_pointers[i][j + 2] = WALL;
}
}
'''2. Parallelize'''
'''3. Optimize'''
