A dynamical search space harmony search for unconstrained optimization problems

A dynamical search space harmony search (DSHS) algorithm in order to improve the efficiency of standard harmony search algorithm. The DSHS employs two strategies which are dynamically changing the search space and ancillary harmony-memory to increase the diversity of harmonies and the global search ability. First the ratio of twin-harmony is defined which is an index of identifying the diversity of harmonies in the Harmony Memory (HM). Then the search space is dynamically changed according to the max ratio of twin-harmony. Finally, ancillary harmony-memories are introduced to replace worse harmonies in the HM, which can keep the main HM from getting into troubles of HM diversity lacking and the local minimum point. Various benchmarks and PID tuning problem are performed to demonstrate the effectiveness of proposed algorithm.