+
+/*
+ Return the 2-log, rounded down
+*/
+template <class T>
+int
+intlog2 (T d)
+{
+ if (d <= 0)
+ error ("intlog2 with negative argument: " + ::to_string (d));
+ int i = 0;
+ while ((d != 1))
+ {
+ d /= 2;
+ i++;
+ }
+
+ assert (! (d / 2));
+ return i;
+}