17 research outputs found

    Layer-wise compressive training for convolutional neural networks

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    Convolutional Neural Networks (CNNs) are brain-inspired computational models designed to recognize patterns. Recent advances demonstrate that CNNs are able to achieve, and often exceed, human capabilities in many application domains. Made of several millions of parameters, even the simplest CNN shows large model size. This characteristic is a serious concern for the deployment on resource-constrained embedded-systems, where compression stages are needed to meet the stringent hardware constraints. In this paper, we introduce a novel accuracy-driven compressive training algorithm. It consists of a two-stage flow: first, layers are sorted by means of heuristic rules according to their significance; second, a modified stochastic gradient descent optimization is applied on less significant layers such that their representation is collapsed into a constrained subspace. Experimental results demonstrate that our approach achieves remarkable compression rates with low accuracy loss (<1%)

    Graphene-PLA (GPLA): A compact and ultra-low power logic array architecture

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    The key characteristics of the next generation of ICs for wearable applications include high integration density, small area, low power consumption, high energy-efficiency, reliability and enhanced mechanical properties like stretchability and transparency. The proper mix of new materials and novel integration strategies is the enabling factor to achieve those design specifications. Moving toward this goal, we introduce a graphene-based regular logic-array structure for energy efficient digital computing. It consists of graphene p-n junctions arranged into a regular mesh. The obtained structure resembles that of Programmable Logic Arrays (PLAs), hence the name Graphene-PLAs (GPLAs); the high expressive power of graphene p-n junctions and their resistive nature enables the implementation of ultra-low power adiabatic logic circuits

    Ultra-low power circuits using graphene p-n junctions and adiabatic computing

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    Recent works have proven the functionality of electrostatically controlled graphene p–n junctions that can serve as basic primitive for the implementation of a new class of compact graphene-based reconfigurable multiplexer logic gates. Those gates, referred as RG-MUXes, while having higher expressive power and better performance w.r.t. standard CMOS gates, they also have the drawback of being intrinsically less power/energy efficient. In this work we address this problem from a circuit perspective, namely, we revisit RG-MUXes as devices that can operate adiabatically and hence with ultra-low (ideally, almost zero) power consumption. More specifically, we show how to build basic logic gates and, eventually, more complex logic functions, by appropriately interconnecting graphene-based p–n junctions as to implement the adiabatic charging principle. We provide a comparison in terms of power and performance against both adiabatic CMOS and their non-adiabatic graphene-based counterparts; characterization results collected from SPICE simulations on a set of representative functions show that the proposed ultra-low power graphene circuits can operate with 1.5–4 orders of magnitude less average power w.r.t. adiabatic CMOS and non-adiabatic graphene counterparts respectively. When it comes to performance, adiabatic graphene shows 1.3 (w.r.t. adiabatic CMOS) to 4.5 orders of magnitude (w.r.t. non-adiabatic technologies) better power-delay product

    Exploiting the Expressive Power of Graphene Reconfigurable Gates via Post-Synthesis Optimization

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    As an answer to the new electronics market demands, semiconductor industry is looking for different materials, new process technologies and alternative design solutions that can support Silicon replacement in the VLSI domain. The recent introduction of graphene, together with the option of electrostatically controlling its doping profile, has shown a possible way to implement fast and power efficient Reconfigurable Gates (RGs). Also, and this is the most important feature considered in this work, those graphene RGs show higher expressive power, i.e., they implement more complex functions, like Majority, MUX, XOR, with less area w.r.t. CMOS counterparts. Unfortunately, state-of-the-art synthesis tools, which have been customized for standard NAND/NOR CMOS gates, do not exploit the aforementioned feature of graphene RGs. In this paper, we present a post-synthesis tool that translates the gate level netlist obtained from commercial synthesis tools to a more optimized netlist that can efficiently integrate graphene RGs. Results conducted on a set of open-source benchmarks demonstrate that the proposed strategy improves, on average, both area and performance by 17% and 8.17% respectively

    CAD Tools for Graphene-Based Electronic Circuits

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    Aggressive feature-size scaling of silicon-based complementary metal-oxide semiconductor (CMOS) transistors is slowly approaching to its ultimate physical limitations. In an era where integrated circuits are supposed to be fast, reliable, and extremely power-efficient, worldwide scientists are striving to find an alternative material that could replace silicon in future electronic devices. During the past decade, graphene, a 2-D allotrope of carbon, has emerged as one of the most promising candidates. Mechanical strength and flexibility, combined with very high carrier mobility, make graphene a perfect material for the implementation of wearable devices. However, pristine graphene is a zero band-gap material, i.e., valence and conductance bands are touching each other near the Dirac points. The direct consequence is an insufficient ON/OFF current ratio that prevents graphene to implement the OFF-state. This poses severe limitations for digital applications, where a clear separation between 0- and 1-logic is fundamental. In this very historical period, most of the worldwide research on the topic is focused on finding practical methods to open the band-gap, in order to match, or at least approach, that of silicon. Available solutions like patterning, chemical doping, or combination with other materials, increase the level of disorder of graphene itself, with rather huge impact on its superlative pristine characteristics, e.g., reduced carrier mobility, in particular. Hence, the need of alternative, fine-tuned, techniques that best suite the mechanical and electrical properties of graphene, while preserving its intrinsic characteristics. The electrostatic doping principle falls in this category. It allows a fine-tuning of the Fermi Energy level in order to obtain equivalent p- or n-type graphene regions using an external electrical field applied through metal gates. Face to face regions with opposite doping profiles form an equivalent p-n junction, the key component behind any electronic circuit. The obtained graphene-based device is what we called Pass-XNOR (PX) gate, since its functionality resembles that of a transmission gate, but with an enhanced built-in logical Exclusive-NOR (XNOR) functionality. From a design-automation perspective, exploiting the expressive power of this new XNOR-based primitive sets a clear departure from classical abstraction models based on the And-Inverter representation, and manipulation, of Boolean logic functions. Therefore, new design methodologies are required to be developed. In this context, the contribution of this work is summarized as follows: (i) we propose a novel integration strategy for PX gates, called the Pass-XNOR Logic (PXL), that fruitfully exploits the built-in XNOR functionality of graphene p-n junctions in order to guarantee compact representations of rather complex Boolean logic functions; (ii) by resorting to the adiabatic charging principle, we demonstrate that PXL circuits are able to reach {\em deep-adiabatic} regimes with a performance improvement of several orders of magnitude w.r.t. silicon counterparts; (iii) we introduce a one-pass synthesis flow for PXL networks by means of a novel abstraction model, called the Pass Diagram, that allows to efficiently manipulate large Boolean networks built upon the XNOR primitive, as well as several synthesis and optimization algorithms which constitute the first CAD tool for graphene-based devices

    One-pass logic synthesis for graphene-based Pass-XNOR logic circuits

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    Electrostatically controlled graphene P-N junctions are devices built on a single layer graphene sheet that can be turned-ON/OFF via external potential difference. Their electrical behavior resembles a CMOS transmission gate with an embedded XNOR Boolean functionality. Recent works presented an efficient design style, the Pass-XNOR logic (PXL), which allows the implementation of adiabatic logic circuits with ultra low-power features. In this work we introduce Gemini, a one-pass logic synthesis methodology for PXL circuits. It consists of a dedicated XNOR-expansion algorithmthat combines logic optimization and technology mapping in a single step carried out through a common data structure, the Pass Diagram. Experimental results demonstrate (i) the superior of PXL circuits in terms of area and performance w.r.t. graphene circuits based on P-N junctions obtained using a CMOS-like synthesis/mapping methodology, and (ii) the power consumption in PXL circuits is governed by the adiabatic-charging principle which guarantees large power/energy savings w.r.t. non-adiabatic counterparts
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