966 research outputs found
A finite state machine synthesizer
This thesis presents a Finite State Machine (FSM) Synthesizer developed at Portland State University. The synthesizer starts from a high level behavioral description, in which no states are specified, and generates the lower level FSM descriptions for simulation and physical layout generation
Approximate logic circuits: Theory and applications
CMOS technology scaling, the process of shrinking transistor dimensions based
on Moore's law, has been the thrust behind increasingly powerful integrated circuits
for over half a century. As dimensions are scaled to few tens of nanometers, process
and environmental variations can significantly alter transistor characteristics, thus
degrading reliability and reducing performance gains in CMOS designs with technology
scaling. Although design solutions proposed in recent years to improve reliability
of CMOS designs are power-efficient, the performance penalty associated with these
solutions further reduces performance gains with technology scaling, and hence these
solutions are not well-suited for high-performance designs.
This thesis proposes approximate logic circuits as a new logic synthesis paradigm
for reliable, high-performance computing systems. Given a specification, an approximate
logic circuit is functionally equivalent to the given specification for a "significant"
portion of the input space, but has a smaller delay and power as compared to a
circuit implementation of the original specification. This contributions of this thesis
include (i) a general theory of approximation and efficient algorithms for automated
synthesis of approximations for unrestricted random logic circuits, (ii) logic design solutions
based on approximate circuits to improve reliability of designs with negligible
performance penalty, and (iii) efficient decomposition algorithms based on approxiiii
mate circuits to improve performance of designs during logic synthesis. This thesis
concludes with other potential applications of approximate circuits and identifies. open
problems in logic decomposition and approximate circuit synthesis
Guarded Evaluation: An Algorithm for Dynamic Power Reduction in FPGAs
Guarded evaluation is a power reduction technique that involves
identifying sub-circuits (within a larger circuit) whose inputs can be
held constant (guarded) at specific times during circuit operation,
thereby reducing switching activity and lowering dynamic power. The
concept is rooted in the property that under certain conditions, some
signals within digital designs are not "observable" at design
outputs, making the circuitry that generates such signals a candidate
for guarding.
Guarded evaluation has been demonstrated successfully
for custom ASICs; in this work, we apply the technique to FPGAs. In
ASICs, guarded evaluation entails adding additional hardware to the
design, increasing silicon area and cost. Here, we apply the technique
in a way that imposes minimal area overhead by leveraging existing
unused circuitry within the FPGA. The LUT functionality is modified
to incorporate the guards and reduce toggle rates.
The primary challenge in guarded evaluation is in determining the specific conditions under which a sub-circuit's
inputs can be held constant without impacting the larger
circuit's functional correctness. We propose a simple solution to
this problem based on discovering gating inputs using "non-inverting paths"
and trimming inputs using "partial non-inverting paths" in the
circuit's AND-Inverter graph representation.
Experimental results show that guarded evaluation can reduce switching activity by
as much as 32% for FPGAs with 6-LUT architectures and 25% for 4-LUT architectures, on
average, and can reduce power consumption in the FPGA interconnect by
29% for 6-LUTs and 27% for 4-LUTs. A clustered architecture with four LUTs to a cluster
and ten LUTs to a cluster produced the best power reduction results.
We implement guarded evaluation at various stages of the FPGA CAD flow and analyze the reductions. We implement
the algorithm as post technology mapping, post packing and post placement optimizations. Guarded Evaluation
as a post technology mapping algorithm inserted the most number of guards and hence achieved the highest activity
and interconnect reduction. However, guarding signals come with a cost of increased fanout and stress on routing
resources. Packing and placement provides the algorithm with additional information of the circuit which is leveraged
to insert high quality guards with minimal impact on routing. Experimental results show that post-packing
and post-placement methods have comparable reductions to post-mapping with considerably lesser impact on the critical
path delay and routability of the circuit
Efficient alternative wiring techniques and applications.
Sze, Chin Ngai.Thesis (M.Phil.)--Chinese University of Hong Kong, 2001.Includes bibliographical references (leaves 80-84) and index.Abstracts in English and Chinese.Abstract --- p.iAcknowledgments --- p.iiiCurriculum Vitae --- p.ivList of Figures --- p.ixList of Tables --- p.xiiChapter 1 --- Introduction --- p.1Chapter 1.1 --- Motivation and Aims --- p.1Chapter 1.2 --- Contribution --- p.8Chapter 1.3 --- Organization of Dissertation --- p.10Chapter 2 --- Definitions and Notations --- p.11Chapter 3 --- Literature Review --- p.15Chapter 3.1 --- Logic Reconstruction --- p.15Chapter 3.1.1 --- SIS: A System for Sequential and Combinational Logic Synthesis --- p.16Chapter 3.2 --- ATPG-based Alternative Wiring --- p.17Chapter 3.2.1 --- Redundancy Addition and Removal for Logic Optimization --- p.18Chapter 3.2.2 --- Perturb and Simplify Logic Optimization --- p.18Chapter 3.2.3 --- REWIRE --- p.21Chapter 3.2.4 --- Implication-tree Based Alternative Wiring Logic Trans- formation --- p.22Chapter 3.3 --- Graph-based Alternative Wiring --- p.24Chapter 4 --- Implication Based Alternative Wiring Logic Transformation --- p.25Chapter 4.1 --- Source Node Implication --- p.25Chapter 4.1.1 --- Introduction --- p.25Chapter 4.1.2 --- Implication Relationship and Implication-tree --- p.25Chapter 4.1.3 --- Selection of Alternative Wire Based on Implication-tree --- p.29Chapter 4.1.4 --- Implication-tree Based Logic Transformation --- p.32Chapter 4.2 --- Destination Node Implication --- p.35Chapter 4.2.1 --- Introduction --- p.35Chapter 4.2.2 --- Destination Node Relationship --- p.35Chapter 4.2.3 --- Destination Node Implication-tree --- p.39Chapter 4.2.4 --- Selection of Alternative Wire --- p.41Chapter 4.3 --- The Algorithm --- p.43Chapter 4.3.1 --- IB AW Implementation --- p.43Chapter 4.3.2 --- Experimental Results --- p.43Chapter 4.4 --- Conclusion --- p.45Chapter 5 --- Graph Based Alternative Wiring Logic Transformation --- p.47Chapter 5.1 --- Introduction --- p.47Chapter 5.2 --- Notations and Definitions --- p.48Chapter 5.3 --- Alternative Wire Patterns --- p.50Chapter 5.4 --- Construction of Minimal Patterns --- p.54Chapter 5.4.1 --- Minimality of Patterns --- p.54Chapter 5.4.2 --- Minimal Pattern Formation --- p.56Chapter 5.4.3 --- Pattern Extraction --- p.61Chapter 5.5 --- Experimental Results --- p.63Chapter 5.6 --- Conclusion --- p.63Chapter 6 --- Logic Optimization by GBAW --- p.66Chapter 6.1 --- Introduction --- p.66Chapter 6.2 --- Logic Simplification --- p.67Chapter 6.2.1 --- Single-Addition-Multiple-Removal by Pattern Feature . . --- p.67Chapter 6.2.2 --- Single-Addition-Multiple-Removal by Combination of Pat- terns --- p.68Chapter 6.2.3 --- Single-Addition-Single-Removal --- p.70Chapter 6.3 --- Incremental Perturbation Heuristic --- p.71Chapter 6.4 --- GBAW Optimization Algorithm --- p.73Chapter 6.5 --- Experimental Results --- p.73Chapter 6.6 --- Conclusion --- p.76Chapter 7 --- Conclusion --- p.78Bibliography --- p.80Chapter A --- VLSI Design Cycle --- p.85Chapter B --- Alternative Wire Patterns in [WLFOO] --- p.87Chapter B.1 --- 0-local Pattern --- p.87Chapter B.2 --- 1-local Pattern --- p.88Chapter B.3 --- 2-local Pattern --- p.89Chapter B.4 --- Fanout-reconvergent Pattern --- p.90Chapter C --- New Alternative Wire Patterns --- p.91Chapter C.1 --- Pattern Cluster C1 --- p.91Chapter C.1.1 --- NAND-NAND-AND/NAND;AND/NAND --- p.91Chapter C.1.2 --- NOR-NOR-OR/NOR;AND/NAND --- p.92Chapter C.1.3 --- AND-NOR-OR/NOR;OR/NOR --- p.95Chapter C.1.4 --- OR-NAND-AND/NAND;AND/NAND --- p.95Chapter C.2 --- Pattern Cluster C2 --- p.98Chapter C.3 --- Pattern Cluster C3 --- p.99Chapter C.4 --- Pattern Cluster C4 --- p.104Chapter C.5 --- Pattern Cluster C5 --- p.105Glossary --- p.106Index --- p.10
Area-power-delay trade-off in logic synthesis
This thesis introduces new concepts to perform area-power-delay trade-offs in a logic synthesis system. To achieve this, a new delay model is presented, which gives accurate delay estimations for arbitrary sets of Boolean expressions. This allows use of this delay model already during the very first steps of logic synthesis. Furthermore, new algorithms are presented for a number of different optimization tasks within logic synthesis. There are new algorithms to create prime irredundant Boo lean expressions, to perform technology mapping for use with standard cell generators, and to perform gate sizing. To prove the validity of the presented ideas, benchmark results are given throughout the thesis
Synthesis and Optimization of Reversible Circuits - A Survey
Reversible logic circuits have been historically motivated by theoretical
research in low-power electronics as well as practical improvement of
bit-manipulation transforms in cryptography and computer graphics. Recently,
reversible circuits have attracted interest as components of quantum
algorithms, as well as in photonic and nano-computing technologies where some
switching devices offer no signal gain. Research in generating reversible logic
distinguishes between circuit synthesis, post-synthesis optimization, and
technology mapping. In this survey, we review algorithmic paradigms ---
search-based, cycle-based, transformation-based, and BDD-based --- as well as
specific algorithms for reversible synthesis, both exact and heuristic. We
conclude the survey by outlining key open challenges in synthesis of reversible
and quantum logic, as well as most common misconceptions.Comment: 34 pages, 15 figures, 2 table
Ontological View-driven Semantic Integration in Open Environments
In an open computing environment, such as the World Wide Web or an enterprise Intranet, various information systems are expected to work together to support information exchange, processing, and integration. However, information systems are usually built by different people, at different times, to fulfil different requirements and goals. Consequently, in the absence of an architectural framework for information integration geared toward semantic integration, there are widely varying viewpoints and assumptions regarding what is essentially the same subject. Therefore, communication among the components supporting various applications is not possible without at least some translation. This problem, however, is much more than a simple agreement on tags or mappings between roughly equivalent sets of tags in related standards. Industry-wide initiatives and academic studies have shown that complex representation issues can arise. To deal with these issues, a deep understanding and appropriate treatment of semantic integration is needed. Ontology is an important and widely accepted approach for semantic integration. However, usually there are no explicit ontologies with information systems. Rather, the associated semantics are implied within the supporting information model. It reflects a specific view of the conceptualization that is implicitly defining an ontological view. This research proposes to adopt ontological views to facilitate semantic integration for information systems in open environments. It proposes a theoretical foundation of ontological views, practical assumptions, and related solutions for research issues. The proposed solutions mainly focus on three aspects: the architecture of a semantic integration enabled environment, ontological view modeling and representation, and semantic equivalence relationship discovery. The solutions are applied to the collaborative intelligence project for the collaborative promotion / advertisement domain. Various quality aspects of the solutions are evaluated and future directions of the research are discussed
Exploring Preconditions for Effective Global Responses to Climate Change
The global response to climate change depends on you⊠and everyone else. The decisions we make, for better or worse, contribute to the global response. This study explores decision making, climate change signals and responses, actors and interests, and the âconditionsâ under which we might limit climate change and related impacts. Twenty-seven experts from around the world were asked to provide scenarios where the global response succeeds or fails to limit climate change and related impacts (i.e. the UNFCCC objective). From their responses, 175 scenarios were compiled forming a âsearchable sample of possible futuresâ. Themes included social change and behaviour, political will and policy, business and economic activity. For these themes, multiple âpathwaysâ were mapped. The study focused on pathways towards effective global responses (i.e. fulfilling the UNFCCC objective) and understanding the most important elements of the response system. The study finds there is a âcrisis of responseâ that risks becoming a âcrisis of impactsâ. The signal that drives effective responses (i.e. impacts on people, property and livelihoods) was undetectable, is detectable now, and is rapidly strengthening. As such, timely global responses at scale are essential. Other preconditions include a mix of ambition and serendipity. From the analysis of effective response scenarios, serendipitous preconditions include the scale of climate change and related impacts being limited and reversible meanwhile unexpected events help limit climate change or related impacts. Ambition driven preconditions include global responses being timely with adaptation, mitigation and atmospheric GHG removals at scale, and having contingencies available in case of extreme climate change or other unexpected events. The transformative scale of required responses means social permissions and leadership are essential, as are coalitions of actors with the capacity to apply technologies and practices (policies included) and power to ensure each of us are contributing towards effective global responses
Sparks of Artificial General Intelligence: Early experiments with GPT-4
Artificial intelligence (AI) researchers have been developing and refining
large language models (LLMs) that exhibit remarkable capabilities across a
variety of domains and tasks, challenging our understanding of learning and
cognition. The latest model developed by OpenAI, GPT-4, was trained using an
unprecedented scale of compute and data. In this paper, we report on our
investigation of an early version of GPT-4, when it was still in active
development by OpenAI. We contend that (this early version of) GPT-4 is part of
a new cohort of LLMs (along with ChatGPT and Google's PaLM for example) that
exhibit more general intelligence than previous AI models. We discuss the
rising capabilities and implications of these models. We demonstrate that,
beyond its mastery of language, GPT-4 can solve novel and difficult tasks that
span mathematics, coding, vision, medicine, law, psychology and more, without
needing any special prompting. Moreover, in all of these tasks, GPT-4's
performance is strikingly close to human-level performance, and often vastly
surpasses prior models such as ChatGPT. Given the breadth and depth of GPT-4's
capabilities, we believe that it could reasonably be viewed as an early (yet
still incomplete) version of an artificial general intelligence (AGI) system.
In our exploration of GPT-4, we put special emphasis on discovering its
limitations, and we discuss the challenges ahead for advancing towards deeper
and more comprehensive versions of AGI, including the possible need for
pursuing a new paradigm that moves beyond next-word prediction. We conclude
with reflections on societal influences of the recent technological leap and
future research directions
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