Abstract
A large and increasing number of Internet-of-Things devices are not equipped with batteries and harvest energy from their environment. Many of them cannot be physically accessed once they are deployed (embedded in civil engineering structures, sent in the atmosphere or deep in the oceans). When they run out of energy, they stop executing and wait until the energy level reaches a threshold. Programming such devices is challenging in terms of ensuring memory consistency and guaranteeing forward progress. Previous work has proposed to insert checkpoints in the program so that execution can resume from well-defined locations. In this work, we propose to define these checkpoint locations based on statically-computed worst-case energy consumption of code sections. We also apply classical compiler optimizations in order to decrease the required number of checkpoints at runtime. As our method is based upon worst-case energy consumption, we can guarantee memory consistency and forward progress.
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Notes
- 1.
A piece of code is idempotent if repeated subsequent invocations do not modify the state of the machine.
- 2.
Even in the presence of multiple return statements in, a function, a compiler can easily create a new block and add edges to it to guarantee a single exit node.
- 3.
The available energy can be related to the capacitance C through the formula \(E=\frac{1}{2}C (V_{start}^2 - V_{stop}^2)\), where \(V_{start}\) and \(V_{stop}\) represent voltages when the capacitor is full, and when the system is forced to stop because the voltage is too low.
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Yarahmadi, B., Rohou, E. (2020). Compiler Optimizations for Safe Insertion of Checkpoints in Intermittently Powered Systems. In: Orailoglu, A., Jung, M., Reichenbach, M. (eds) Embedded Computer Systems: Architectures, Modeling, and Simulation. SAMOS 2020. Lecture Notes in Computer Science(), vol 12471. Springer, Cham. https://doi.org/10.1007/978-3-030-60939-9_12
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