David Stone has spoken at C++Now and Meeting C++. He is the author of the bounded::integer library: http://doublewise.net/c++/bounded/ and has a special interest in compile-time code generation and error checking, as well as machine learning. He works at Markit integrating real-time financial data.
He has written an algorithm that solved the traveling salesman problem in polynomial time. He can square the circle and divide by zero. He can move his king into check. He once wrote an optimizing compiler that solved the halting problem, but doesn't need to use it because his code is already optimized.