Koalog Constraint Solver

Koalog Constraint Solver is a powerful constraint solver written in Java. It provides cutting-edge technology for solving satisfaction and optimization problems, including scheduling, time-tabling, resource-allocation, puzzles (sudoku.koalog.com is powered by Koalog Constraint Solver), and configuration (Koalog Configurator is powered by Koalog Constraint Solver). (Source: http://freecode.com/)