"We present a novel conservative algorithm based on the classical Chandy-Misra-Bryant (CMB) synchronization mechanism by extending DEVS abstract simulator to provide means for look-ahead computation and null-message distribution. We integrate this mechanism into the CD++ simulation toolkit, providing a purely conservative simulator for running large-scale DEVS and Cell-DEVS models. Our algorithm is implemented on a revised DEVS abstract simulator to reduce the frequency of look-ahead computation. It also replaces time information estimations with a single lookahead computation, causing reduction in the number of null-messages. The dynamic lookahead values of the proposed algorithm are extracted from the model specification and the user is not required to provide lookahead values prior to the execution. In addition, the low-cost lookahead computation feature of the algorithm provides a fast and efficient method and reduces overhead."--From the paper.