An efficient algorithm in the HLA time management

The HLA time management is an important factor that limits the scalability of distributed simulations. An efficient algorithm of Greatest Available Logical Time (GALT) is thus much critical for the time management in an RTI to support large-scale simulations. The concept of GALT in IEEE 1516 was also called Lower Bound Time Stamp (LBTS) in HLA 1.3. The computation of GALT in the HLA time management is different from that of LBTS in traditional Parallel Discrete Event Simulation (PDES). In this paper, an algorithm about GALT is presented and its correctness is proved. Its efficiency is also explained by applying it to RTI1.3-NG. In fact, the algorithm has been implemented in our RTI to support thousands of federates in our cluster systems. In addition, a real-world example is introduced to explain the correctness of the algorithm proving, and the reason of our RTI supporting large-scale simulations.