Jump to content

File:Backtang2.png

Page contents not supported in other languages.
This is a file from the Wikimedia Commons
From Wikipedia, the free encyclopedia

Original file (1,024 × 1,024 pixels, file size: 143 KB, MIME type: image/png)

Summary

Description
Italiano: Bak–Tang–Wiesenfeld sandpile, 28 million grains
Date
Source Own work
Author Claudio Rocchini

Licensing

I, the copyright holder of this work, hereby publish it under the following license:
w:en:Creative Commons
attribution
This file is licensed under the Creative Commons Attribution 3.0 Unported license.
You are free:
  • to share – to copy, distribute and transmit the work
  • to remix – to adapt the work
Under the following conditions:
  • attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.

Source Code

#include <stdio.h>
#include <stdlib.h>
#include <queue>

typedef unsigned char byte;
typedef std::pair<int,int> coord;
const int    N = 1024;
const size_t C = 4;
const size_t S = 28000000;

byte M[N][N];
const int dx[4] = {1,0,-1,0}; 
const int dy[4] = {0,1,0,-1};

int main() {
    memset(M,0,N*N);
	
    for(size_t steps=0;steps<S;++steps) {
        std::queue<coord> q;
        if( ++M[N/2][N/2]>=C ) q.push( coord(N/2,N/2) );
        while( !q.empty() ) {
            const int x = q.front().first;
            const int y = q.front().second;
            q.pop();
            if(M[x][y]<C) continue;
            M[x][y] -= 4;
            for(int d=0;d<4;++d) {
                const int lx = x+dx[d];
                const int ly = y+dy[d];
                if(lx<0 || lx>=N) continue;
                if(ly<0 || ly>=N) continue;
		if(++M[lx][ly]>=C) q.push( coord(lx,ly) );
            }
        }
    }

    const byte co[4][3] = { {255,255,255}, {255,0,0}, {0,255,0}, {0,0,255} };
    FILE * fo = fopen("backtang2.ppm","wb");
    fprintf(fo,"P6\n%d %d\n255\n",N,N);
    for(int x=0;x<N;++x) for(int y=0;y<N;++y)
        fwrite(co[M[x][y]],1,3,fo);
    fclose(fo);

    return 0;
}

Captions

Add a one-line explanation of what this file represents

Items portrayed in this file

depicts

7 August 2012

image/png

f5e634e4c4716f43272e8c88965e575c784c5278

145,948 byte

1,024 pixel

1,024 pixel

File history

Click on a date/time to view the file as it appeared at that time.

Date/TimeThumbnailDimensionsUserComment
current09:27, 7 August 2012Thumbnail for version as of 09:27, 7 August 20121,024 × 1,024 (143 KB)Rocchini

The following page uses this file:

Global file usage

The following other wikis use this file: