Percolation/Mean cluster density: Difference between revisions
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;See also |
;See also |
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* [http://mathworld.wolfram.com/s-Cluster.html s-Cluster] on Wolfram mathworld. |
* [http://mathworld.wolfram.com/s-Cluster.html s-Cluster] on Wolfram mathworld. |
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=={{header|C}}== |
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<lang c>#include <stdio.h> |
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#include <stdlib.h> |
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int *map, w, ww; |
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void make_map(double p) |
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{ |
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int i, thresh = RAND_MAX * p; |
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i = ww = w * w; |
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map = realloc(map, i * sizeof(int)); |
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while (i--) map[i] = -(rand() < thresh); |
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} |
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char alpha[] = "+.ABCDEFGHIJKLMNOPQRSTUVWXYZ" |
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"abcdefghijklmnopqrstuvwxyz"; |
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#define ALEN ((int)(sizeof(alpha) - 3)) |
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void show_cluster(void) |
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{ |
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int i, j, *s = map; |
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for (i = 0; i < w; i++) { |
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for (j = 0; j < w; j++, s++) |
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printf(" %c", *s < ALEN ? alpha[1 + *s] : '?'); |
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putchar('\n'); |
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} |
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} |
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void recur(int x, int v) { |
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if (x >= 0 && x < ww && map[x] == -1) { |
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map[x] = v; |
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recur(x - w, v); |
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recur(x - 1, v); |
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recur(x + 1, v); |
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recur(x + w, v); |
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} |
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} |
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int count_clusters(void) |
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{ |
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int i, cls; |
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for (cls = i = 0; i < ww; i++) { |
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if (-1 != map[i]) continue; |
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recur(i, ++cls); |
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} |
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return cls; |
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} |
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double tests(int n, double p) |
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{ |
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int i; |
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double k; |
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for (k = i = 0; i < n; i++) { |
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make_map(p); |
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k += (double)count_clusters() / ww; |
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} |
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return k / n; |
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} |
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int main(void) |
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{ |
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w = 15; |
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make_map(.5); |
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printf("width=15, p=0.5, %d clusters:\n", count_clusters()); |
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show_cluster(); |
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printf("\np=0.5, iter=5:\n"); |
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for (w = 1<<2; w <= 1<<14; w<<=2) |
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printf("%5d %9.6f\n", w, tests(5, .5)); |
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free(map); |
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return 0; |
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}</lang> |
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{{out}} |
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<pre> |
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width=15, p=0.5, 23 clusters: |
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A . . . B . C C C C . D . E . |
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A . . B B . . . . . . . . . . |
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A . . . . . F . . G . H . . I |
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. . J J J . . K K . L . M . I |
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. J J . . . K K K K . M M . . |
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. . . . K K . K . K . M . N . |
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O O . K K K . K . . . . N N N |
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. O O . K K K K K . P . N . . |
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Q . . K K . . . K . P . . . . |
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. R . K K . . K K . P . . S . |
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. . K K . . . . K . P . . . K |
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K K K K K . . K K . . T . . K |
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K . K . . . U . K . . T . . . |
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K . K K K K . K K K . T . . . |
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. . K . K . V . K K . . . W . |
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p=0.5, iter=5: |
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4 0.125000 |
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16 0.083594 |
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64 0.064453 |
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256 0.066864 |
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1024 0.065922 |
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4096 0.065836 |
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16384 0.065774 |
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</pre> |
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=={{header|D}}== |
=={{header|D}}== |
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