Percolation/Bond percolation: Difference between revisions
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"p=9/10 -> 0.0000"
"p=10/10 -> 0.0000"
</pre>
=={{header|Java}}==
<syntaxhighlight lang="java">
import java.util.Arrays;
import java.util.concurrent.ThreadLocalRandom;
public final class PercolationBond {
public static void main(String[] aArgs) {
System.out.println("Sample percolation with a " + COL_COUNT + " x " + ROW_COUNT + " grid:");
makeGrid(0.5);
percolate();
showGrid();
System.out.println("Using 10,000 repetitions for each probability p:");
for ( int p = 1; p <= 9; p++ ) {
int percolationCount = 0;
double probability = p / 10.0;
for ( int i = 0; i < 10_000; i++ ) {
makeGrid(probability);
if ( percolate() ) {
percolationCount += 1;
}
}
final double percolationProportion = (double) percolationCount / 10_000;
System.out.println(String.format("%s%.1f%s%.4f", "p = ", probability, ": ", percolationProportion));
}
}
private static void makeGrid(double aProbability) {
Arrays.fill(grid, 0);
for ( int i = 0; i < COL_COUNT; i++ ) {
grid[i] = LOWER_WALL | RIGHT_WALL;
}
endOfRow = COL_COUNT;
for ( int i = 0; i < ROW_COUNT; i++ ) {
for ( int j = COL_COUNT - 1; j >= 1; j-- ) {
final boolean chance1 = RANDOM.nextDouble() < aProbability;
final boolean chance2 = RANDOM.nextDouble() < aProbability;
grid[endOfRow++] = ( chance1 ? LOWER_WALL : 0 ) | ( chance2 ? RIGHT_WALL : 0 );
}
final boolean chance3 = RANDOM.nextDouble() < aProbability;
grid[endOfRow++] = RIGHT_WALL | ( chance3 ? LOWER_WALL : 0 );
}
}
private static void showGrid() {
for ( int j = 0; j < COL_COUNT; j++ ) {
System.out.print("+--");
}
System.out.println("+");
for ( int i = 0; i < ROW_COUNT; i++ ) {
System.out.print("|");
for ( int j = 0; j < COL_COUNT; j++ ) {
System.out.print( ( ( grid[i * COL_COUNT + j + COL_COUNT] & FILL ) != 0 ) ? "[]" : " " );
System.out.print( ( ( grid[i * COL_COUNT + j + COL_COUNT] & RIGHT_WALL ) != 0 ) ? "|" : " " );
}
System.out.println();
for ( int j = 0; j < COL_COUNT; j++ ) {
System.out.print( ( ( grid[i * COL_COUNT + j + COL_COUNT] & LOWER_WALL) != 0 ) ? "+--" : "+ " );
}
System.out.println("+");
}
System.out.print(" ");
for ( int j = 0; j < COL_COUNT; j++ ) {
System.out.print( ( ( grid[ROW_COUNT * COL_COUNT + j + COL_COUNT] & FILL ) != 0 ) ? "[]" : " " );
System.out.print( ( ( grid[ROW_COUNT * COL_COUNT + j + COL_COUNT] & RIGHT_WALL ) != 0 ) ? "|" : " " );
}
System.out.println(System.lineSeparator());
}
private static boolean fill(int aGridIndex) {
if ( ( grid[aGridIndex] & FILL ) != 0 ) {
return false;
}
grid[aGridIndex] |= FILL;
if ( aGridIndex >= endOfRow ) {
return true;
}
return ( ( ( grid[aGridIndex] & LOWER_WALL ) == 0 ) && fill(aGridIndex + COL_COUNT) ) ||
( ( ( grid[aGridIndex] & RIGHT_WALL ) == 0 ) && fill(aGridIndex + 1) ) ||
( ( ( grid[aGridIndex - 1] & RIGHT_WALL ) == 0 ) && fill(aGridIndex - 1) ) ||
( ( ( grid[aGridIndex - COL_COUNT] & LOWER_WALL ) == 0 ) && fill(aGridIndex - COL_COUNT) );
}
private static boolean percolate() {
int i = 0;
while ( i < COL_COUNT && ! fill(COL_COUNT + i) ) {
i++;
}
return i < COL_COUNT;
}
private static final int ROW_COUNT = 10;
private static final int COL_COUNT = 10;
private static int endOfRow = COL_COUNT;
private static int[] grid = new int[COL_COUNT * ( ROW_COUNT + 2 )];
private static final int FILL = 1;
private static final int RIGHT_WALL = 2;
private static final int LOWER_WALL = 4;
private static final ThreadLocalRandom RANDOM = ThreadLocalRandom.current();
}
</syntaxhighlight>
{{ out }}
<pre>
Sample percolation with a 10 x 10 grid:
+--+--+--+--+--+--+--+--+--+--+
|[] []|[]| | | |
+--+--+ +--+--+ +--+ +--+--+
| | |[] | | |
+ + + +--+ + +--+ + + +
| | []| | | |
+ +--+ +--+--+ + +--+--+--+
| |[] | | |
+ +--+ +--+--+--+ +--+--+--+
| | []| | | | | | |
+--+ + + +--+--+ + +--+ +
| |[] | | | | |
+--+ + + + +--+--+ + +--+
| [] []| | | |
+ + +--+--+ +--+--+--+ +--+
| |[] | | | | |
+ + +--+ +--+ + +--+ + +
| []| | | | | |
+ + +--+ +--+--+--+--+ + +
| |[] [] | |
+ +--+ +--+--+ +--+ +--+--+
[]
Using 10,000 repetitions for each probability p:
p = 0.1: 1.0000
p = 0.2: 0.9999
p = 0.3: 0.9973
p = 0.4: 0.9223
p = 0.5: 0.5011
p = 0.6: 0.0872
p = 0.7: 0.0022
p = 0.8: 0.0000
p = 0.9: 0.0000
</pre>
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