55 research outputs found
Parameterized Algorithms for Graph Partitioning Problems
We study a broad class of graph partitioning problems, where each problem is
specified by a graph , and parameters and . We seek a subset
of size , such that is at most
(or at least) , where are constants
defining the problem, and are the cardinalities of the edge sets
having both endpoints, and exactly one endpoint, in , respectively. This
class of fixed cardinality graph partitioning problems (FGPP) encompasses Max
-Cut, Min -Vertex Cover, -Densest Subgraph, and -Sparsest
Subgraph.
Our main result is an algorithm for any problem in
this class, where is the maximum degree in the input graph.
This resolves an open question posed by Bonnet et al. [IPEC 2013]. We obtain
faster algorithms for certain subclasses of FGPPs, parameterized by , or by
. In particular, we give an time algorithm for Max
-Cut, thus improving significantly the best known time
algorithm
3D IC optimal layout design. A parallel and distributed topological approach
The task of 3D ICs layout design involves the assembly of millions of
components taking into account many different requirements and constraints such
as topological, wiring or manufacturability ones. It is a NP-hard problem that
requires new non-deterministic and heuristic algorithms. Considering the time
complexity, the commonly applied Fiduccia-Mattheyses partitioning algorithm is
superior to any other local search method. Nevertheless, it can often miss to
reach a quasi-optimal solution in 3D spaces. The presented approach uses an
original 3D layout graph partitioning heuristics implemented with use of the
extremal optimization method. The goal is to minimize the total wire-length in
the chip. In order to improve the time complexity a parallel and distributed
Java implementation is applied. Inside one Java Virtual Machine separate
optimization algorithms are executed by independent threads. The work may also
be shared among different machines by means of The Java Remote Method
Invocation system.Comment: 26 pages, 9 figure
Recent Advances in Graph Partitioning
We survey recent trends in practical algorithms for balanced graph
partitioning together with applications and future research directions
Investigation of performance metrics for interconnect stack architectures
This paper discusses metrics involving the bandwidth and energy characteristics of arbitrary interconnect stacks. Front-end dimensions are set by lithography and related fabrication restrictions and its performance is easily quantified using well-known metrics such as FO4 or ring oscillator delays, Ioff, and Ion. Back-end dimensions are not similarly constrained yet there are no comparable back-end metrics. In this study we seek figures-of-merit for interconnect architectures (stacks) that describe performance in terms of bandwidth and energy while considering issues such as via blockage and repeaters. A definition of bandwidth is presented and then appropriate via blockage models for interconnect stacks are investigated. In this paper, we improve existing bandwidth and throughput-driven design methodologies by looking at the entire stack rather than a single wiring layer. We also propose the use of bandwidth per unit energy. We evaluate and discuss these metrics in current 130nm and 90nm interconnect technologies
Toward better wireload models in the presence of obstacles
Efficient and accurate interconnect estimation is crucial to design convergence. With System-on-Chip design, IP blocks form routing obstacles that cannot be accounted for by existing a priori wirelength estimations. In this paper, we identify two distinct effects of obstacles on interconnection length: (i) changes due to the redistribution of interconnect terminals and (ii) detours that have to be made around the obstacles. Theoretical expressions of both effects for point-to-point nets with a single obstacle are derived and compared to experimental observations. We also experimentally assess these effects for multi-terminal interconnections and in the presence of multiple obstacles. We single out cases where the effects are additive, which suggests the use of lookup tables and equivalent blockage relations. Our results are applicable in chip planning tools, where they enable improved accounting for obstacles in a priori wirelength estimation schemes
Designing a Processor From the Ground Up to Allow Voltage/Reliability Tradeoffs
Current processor designs have a critical operating point that sets a hard limit on voltage scaling. Any scaling beyond the critical voltage results in exceeding the maximum allowable error rate, i.e., there are more timing errors than can be effectively and gainfully detected or corrected by an error-tolerance mechanism. This limits the effectiveness of voltage scaling as a knob for reliability/power tradeoffs. In this paper, we present power-aware slack redistribution, a novel design-level approach to allow voltage/reliability tradeoffs in processors. Techniques based on power-aware slack redistribution reapportion timing slack of the frequently-occurring, near-critical timing paths of a processor in a power- and area-efficient manner, such that we increase the range of voltages over which the incidence of operational (timing) errors is acceptable. This results in soft architectures - designs that fail gracefully, allowing us to perform reliability/power tradeoffs by reducing voltage up to the point that produces maximum allowable errors for our application. The goal of our optimization is to minimize the voltage at which a soft architecture encounters the maximum allowable error rate, thus maximizing the range over which voltage scaling is possible and minimizing power consumption for a given error rate. Our experiments demonstrate 23% power savings over the baseline design at an error rate of 1%. Observed power reductions are 29%, 29%, 19%, and 20% for error rates of 2%, 4%, 8%, and 16% respectively. Benefits are higher in the face of error recovery using Razor. Area overhead of our techniques is up to 2.7%
More realistic power grid verification based on hierarchical current and power constraints
Vectorless power grid verification algorithms, by solving linear programming (LP) problems under current constraints, enable worst-case voltage drop predictions at an early design stage. However, worst-case current patterns obtained by many existing vectorless algorithms are time-invariant (i.e., are constant throughout the simulation time), which may result in an overly pessimistic voltage drop prediction. In this paper, a more realistic power grid verification algorithm based on hierarchical current and power constraints is proposed. The proposed algorithm naturally handles general RCL power grid models. Currents at different time steps are treated as independent variables and additional power constraints are introduced; this results in more realistic time-varying worst-case current patterns and less pessimistic worst-case voltage drop predictions. Moreover, a sorting-deletion algorithm is proposed to speed up solving LP problems by utilizing the hierarchical constraint structure. Experimental results confirm that worst-case current patterns and voltage drops obtained by the proposed algorithm are more realistic, and that the sorting-deletion algorithm reduces runtime needed to solve LP problems by 85%. © 2011 ACM.link_to_OA_fulltextThe 2011 ACM/IEEE International Symposium on Physical Design (ISPD 2011), Santa Barbara, CA., 27-30 March 2011. In Proceedings of the International Symposium on Physical Design, 2011, p. 159-16
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