estimate calc utility (WIP)

calcest.c

@@ -0,0 +1,43 @@
+#include <stdio.h>
+#include <math.h>
+
+/*
+ * as per scribblemaniac's explanation:
+ * t - number of trials
+ * n - character count
+ * p - probability
+ * condition: >=1 matches
+ * formula: t = log(1-p)/log(1-1/32^n)
+ * comes from:
+ *  distribution X~Binomial(t, 1/32^n)
+ *  P(X>=1)=p
+ */
+
+const double probs[] = { 0.5, 0.8, 0.9, 0.95, 0.99 };
+const int charcounts[] = { 2, 3, 4, 5, 6, 7 };
+
+int main(void)
+{
+	printf("   |");
+	for (int i = 0; i < sizeof(probs)/sizeof(probs[0]); ++i) {
+		printf(" %11d%% |",(int)((probs[i]*100)+0.5));
+	}
+	printf("\n");
+
+	printf("---+");
+	for (int i = 0; i < sizeof(probs)/sizeof(probs[0]); ++i) {
+		printf("--------------+");
+	}
+	printf("\n");
+
+	for (int i = 0; i < sizeof(charcounts)/sizeof(charcounts[0]); ++i) {
+		printf("%2d |",charcounts[i]);
+		for (int j = 0; j < sizeof(probs)/sizeof(probs[0]); ++j) {
+			double t = log2(1 - probs[j]) / log2(1 - (1 / pow(32,charcounts[i])));
+			printf(" %12.0f |",t);
+		}
+		printf("\n");
+	}
+
+	return 0;
+}