Data commit

Task/Percolation-Mean-run-density/C/percolation-mean-run-density.c

@@ -0,0 +1,36 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+// just generate 0s and 1s without storing them
+double run_test(double p, int len, int runs)
+{
+	int r, x, y, i, cnt = 0, thresh = p * RAND_MAX;
+
+	for (r = 0; r < runs; r++)
+		for (x = 0, i = len; i--; x = y)
+			cnt += x < (y = rand() < thresh);
+
+	return (double)cnt / runs / len;
+}
+
+int main(void)
+{
+	double p, p1p, K;
+	int ip, n;
+
+	puts(	"running 1000 tests each:\n"
+		" p\t   n\tK\tp(1-p)\t     diff\n"
+		"-----------------------------------------------");
+	for (ip = 1; ip < 10; ip += 2) {
+		p = ip / 10., p1p = p * (1 - p);
+
+		for (n = 100; n <= 100000; n *= 10) {
+			K = run_test(p, n, 1000);
+			printf("%.1f\t%6d\t%.4f\t%.4f\t%+.4f (%+.2f%%)\n",
+				p, n, K, p1p, K - p1p, (K - p1p) / p1p * 100);
+		}
+		putchar('\n');
+	}
+
+	return 0;
+}