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Usás

Battery-free continuous learning on solar-powered edge servers.

HPCA 2024

The problem

Battery-powered edge ML works until the battery doesn’t. Grid power isn’t always available where the data is. Solar is — but solar is intermittent in a way that conventional fixed-shape accelerators handle badly: when the panel goes quiet, training stalls; when it comes back, the model has to catch up on stale data.

What Usás does

A morphable DNN accelerator that dynamically resizes its systolic array to match the available power envelope. When the panel is feeding a healthy current, the accelerator runs wide. When it dims, the array contracts and the active partition keeps making forward progress instead of stalling.

A teacher-student training procedure keeps the smaller network useful: a heavier teacher model — trained when power permits — distills into a student that’s the active inference path under power-constrained windows.

A micro-profiling engine picks hyperparameters under hard power budgets, and a non-battery design stores minimal energy in capacitors plus aggressive checkpointing for resumability.

Results

About 5% higher accuracy over a multi-window horizon than conventional continuous-learning approaches at the same power budget, and hundreds of kWh per year per device saved compared to battery-buffered baselines.

Why it matters

This is the architectural answer to the question “how does ML happen where the grid doesn’t reach?” — not by shrinking the model until it fits a tiny battery, but by reshaping the silicon to match the energy that’s actually available.