DyMeLoR: Dynamic Memory Logger and Restorer Library for Optimistic Simulation Objects with Generic Memory Layout

In this article we focus on checkpoint/restore facilities for optimistic simulation objects with generic memory layout. Specifically, we present the design and implementation of a C library, named DyMeLoR (Dynamic Memory Logger and Restorer), that, beyond offering traditional services for dynamic memory allocation/release, additionally supports transparent checkpoint/restore of scattered simulation objects´ states. DyMeLoR is well suited for being integrated within optimistic simulation platforms relying on kernel processes, each managing one or more simulation objects, as typical in most implementations of general purpose optimistic simulation platforms. From the point of view of efficiency, DyMeLoR has been designed in order to minimize memory consumption for meta-data describing the current layout of the simulation object´s state, and to provide good trade-offs between the cost of meta-data manipulation and the cost of memory-to-memory data copies associated with checkpoint/restore tasks. Also, the library exhibits Piece-Wise-Deterministic (PWD) behavior, thus allowing the employment of (optimized) sparse checkpointing strategies each time the overlying application software complies with the PWD assumption. We also report the results of an experimental study where DyMeLoR is integrated within the ROme OpTimistic Simulator (ROOT-Sim), and is used to support optimistic simulation of a cellular system.