Providing determinism in the Time Warp operating system-costs, benefits, and implications

The Time Warp operating system runs discrete event simulations on parallel hardware. One requirement of the system is that simulations produce deterministic results identical to sequential runs of the same programs. Providing this level of determinism on parallel hardware has required care in designing the system and discipline by applications writers, but it also has benefits. It has assisted in detecting a number of errors in both the system and its applications, and has allowed the use of a special debugging tool that has proved valuable in dealing with such errors. Some of the reasons for providing determinism, the problems of doing so, and the benefits of determinism are discussed.<>