SYMPHONY requires the use of a third-party callable library to solve the LP relaxations once they are formulated. Native interfaces to ILOG's CPLEX and IBM's OSL are available. As of Version 4.0, the Open Solver Interface, available from COIN . can be used to interface with most commonly available LP solvers. The list of solvers with OSI interfaces currently numbers eight and includes both commercial and open source alternatives. If the COIN libraries are used, make sure to set the proper paths in the SYMPHONY makefile.