X-Git-Url: http://git.tremily.us/?a=blobdiff_plain;f=bisect.c;h=bd1b7b5dac81ada592a16630214d1f2cbb655b88;hb=9798f7e5f948b2586c33d850f6a00d4fc0537d75;hp=1aad49b1a642a308f449001960958ccab79347d1;hpb=e034d1bb927c17a3406a2bdbb8ccf710677a139d;p=git.git

diff --git a/bisect.c b/bisect.c
index 1aad49b1a..bd1b7b5da 100644
--- a/bisect.c
+++ b/bisect.c
@@ -956,3 +956,41 @@ int bisect_next_all(const char *prefix, int no_checkout)
 	return bisect_checkout(bisect_rev_hex, no_checkout);
 }
 
+static inline int log2i(int n)
+{
+	int log2 = 0;
+
+	for (; n > 1; n >>= 1)
+		log2++;
+
+	return log2;
+}
+
+static inline int exp2i(int n)
+{
+	return 1 << n;
+}
+
+/*
+ * Estimate the number of bisect steps left (after the current step)
+ *
+ * For any x between 0 included and 2^n excluded, the probability for
+ * n - 1 steps left looks like:
+ *
+ * P(2^n + x) == (2^n - x) / (2^n + x)
+ *
+ * and P(2^n + x) < 0.5 means 2^n < 3x
+ */
+int estimate_bisect_steps(int all)
+{
+	int n, x, e;
+
+	if (all < 3)
+		return 0;
+
+	n = log2i(all);
+	e = exp2i(n);
+	x = all - e;
+
+	return (e < 3 * x) ? n : n - 1;
+}