AP3M is an adaptive particle-particle, particle-mesh code. It is older than Hydra (ascl:1103.010) but faster and more memory-efficient for dark-matter only calculations. The Adaptive P3M technique (AP3M) is built around the standard P3M algorithm. AP3M produces fully equivalent forces to P3M but represents a more efficient implementation of the force splitting idea of P3M. The AP3M program may be used in any of the three modes with an appropriate choice of input parameter.