The definition of entropy indeed includes in it the convention that 0*log(0) = 0 http://en.wikipedia.org/wiki/Entropy_%28information_theory%29#Definition This convention is justified by the fact that p log p --> 0 as p --> 0.
Implement remaining part of Algorithm 2. Separate C++ code from header files. Implement and use ostream& operator<<(ostream& o, const Partition &p). Implement number_of_cell_points(int row, int col) and use it in hpq(). Make clumps and q in ExtensiblePartition static pointers.