A VP-accordant checkpointing protocol preventing useless checkpoints

A useless checkpoint corresponds to the occurrence of a checkpoint and communication pattern called Z-cycle. A recent result shows that ensuring a computation without Z-cycles is a particular application of a property, namely Virtual Precedence (VP), defined on an interval-based abstraction of a computation. We first propose a taxonomy of communication-induced checkpointing protocols based on the way they ensure the VP property. Then we derive a sufficient condition ensuring no Z-cycles in a distributed computation. This condition defines a checkpoint and communication pattern, namely suspect Z-cycle, such that if no suspect Z-cycle exists in a distributed computation then no Z-cycle exists. We present finally a communication-induced checkpointing protocol that avoids useless checkpoints by preventing on-the-fly the formation of suspect Z-cycles and discuss its performance with respect to other protocols.