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Alexios Birbas

Publications and source records attributed to Alexios Birbas.

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NAS-Driven Hardware Accelerator Exploration for Edge AI and Quantization Effects on the Pareto Space

Edge AI deployment demands neural architectures that are simultaneously accurate, computationally efficient, and hardware-deployable - a challenge addressed by hardware-aware Neural Architecture Search (NAS). While recent works incorporate quantization directly into the NAS loop, these approaches expand search complexity and tightly couple architecture and quantization design. The simpler post-search quantization strategy has received little analytical attention: the effects of Post-Training Quantization (PTQ) on the NAS-discovered Pareto structure remain uncharacterised, and no framework combines quantized architecture mapping onto reconfigurable accelerators with automated hardware exploration. This paper addresses both gaps. First, a three-stage pipeline is proposed: a hardware-agnostic Pareto rank surrogate frontend on NAS-Bench-201, a quantization bridge with Pareto-aware filtering and feedback control, and an evolutionary Domain Space Exploration (DSE) backend on CGRA4ML for optimal hardware mapping. Second, an empirical study characterises how INT4 PTQ perturbs the NAS-Bench-201 Pareto space through formal stability metrics on ground-truth data for all 15,625 architectures, and demonstrates that an FP32 zero-shot surrogate outperforms a dedicated INT4-trained surrogate in Pareto space coverage across two standard search strategies.

cs.AI

A 100-ps Multi-Time over Threshold Data Acquisition System for Cosmic Ray Detection

High-energy cosmic rays are one of the primary sources of information for scientists investigating the elementary properties of matter. The need to study cosmic rays, with energies thousands of times larger than those encountered in particle accelerators, led to the development of modern detection hardware and experimental methodologies. We present a low power, low complexity data acquisition (DAQ) system with 100 ps resolution, suitable for particle and radiation detection experiments. The system uses a Multiple-Time-over-Threshold (MToT) technique for the treatment of the output signal of Photo Multiplier Tubes (PMTs). The use of three thresholds compensates for the slewing effects and offers a more accurate measurement of the PMT pulses' width. For the evaluation of the pulse the system uses comparators and a Time-to-Digital (TDC) converter, whereas the pulses are time-stamped using the GPS signal. The prototype card is analyzed for its noise behavior and is tested to verify its performance. The system has been designed for the HEllenic LYceum Cosmic Observatories Network (HELYCON) Extensive Air Showers (EAS) detector.

physics.ins-det