Checkpointing Parallel Subsystems for Consistent Program Recovery

The patent applies preliminary action by recording not only the program state at checkpoint moments but also all external stimuli (input data, environmental parameters, system events) that occur between checkpoints. This allows the replay process to reconstruct the exact execution conditions that led to the original program behavior, thereby maintaining both reliability and behavioral accuracy during recovery operations.

The patent segments the checkpointing system into distinct functional components: a state recording module that captures program counter and register values, an external stimuli recording module that captures input data and environmental conditions, and a replay coordination module that manages the reconstruction process. This segmentation allows each component to be optimized independently and simplifies the overall system architecture while maintaining comprehensive recording capabilities.

The patent implements periodic action by establishing checkpoints at regular intervals during program execution rather than continuously. Between these periodic checkpoints, the system maintains normal high-speed execution. The checkpoint frequency is optimized to capture sufficient external stimuli information for accurate replay while minimizing the performance overhead, achieving a balance between replication accuracy and productivity.