Kalliopi Tsota

Purdue University, West Lafayette, IN, United States

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Publications (4)0 Total impact

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    ABSTRACT: One of the necessary requirements for the placement process is that it should be capable of generating routable solutions. This paper describes a simple but effective method leading to the reduction of the routing congestion and the final routed wirelength for large-scale mixed-size designs. In order to reduce routing congestion and improve routability, we propose blocking narrow regions on the chip. We also propose dummy-cell insertion inside regions characterized by reduced fixed-macro density. Our placer consists of three major components: (i) narrow channel reduction by performing neighbor-based fixed-macro inflation; (ii) dummy-cell insertion inside large regions with reduced fixed-macro density; and (iii) pre-placement inflation by detecting tangled logic structures in the netlist and minimizing the maximum pin density. We evaluated the quality of our placer using the newly released DAC 2012 routability-driven placement contest designs and we compared our results to the top four teams that participated in the placement contest. The experimental results reveal that our placer improves the routability of the DAC 2012 placement contest designs and effectively reduces the routing congestion.
    Design Automation Conference (ASP-DAC), 2013 18th Asia and South Pacific; 01/2013
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    ABSTRACT: This paper studies the effects of clustering as a pre-processing step and routability estimation in the placement flow. The study shows that when clustering and routability estimation are considered, the placer effectively improves the routed wirelength for the circuits of IBM-PLACE 2.0 standard-cell Benchmark Suite [1] and results in the best average routed wirelength when compared against state-of-the-art academic placers.
    2009 International Conference on Computer-Aided Design (ICCAD'09), November 2-5, 2009, San Jose, CA, USA; 01/2009
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    ABSTRACT: This paper presents an efficient technique for the estimation of the routed wirelength during global placement using the wire density of the net. The proposed method identifies congested regions of the chip and incorporates the model of the routed wirelength into the objective function in order to effectively alleviate these regions from congestion. The method is integrated in the analytical placement framework and the two-level structure improves the scalability of the placer and speeds up the algorithm. The proposed analytical placer provides the best-so-far average routed wirelength in the IBM version2 benchmark suite.
    2008 International Conference on Computer-Aided Design (ICCAD'08), November 10-13, 2008, San Jose, CA, USA; 01/2008
  • Kalliopi Tsota
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    ABSTRACT: Very large scale integration (VLSI) has been a central technology for the realization of modern-day systems. The number of components in a VLSI design may run in the billions and it continues to grow, while the advantages associated with these advances are realized in multiple fields. However, the increased complexity of the designs poses new challenges for today's electronic design automation. ^ VLSI computer-aided design tools have to address the effects of technology scaling on interconnects. More specifically, interconnect delay has become a dominant factor in modern designs. During the physical design process, placement of the components on a chip and routing of the connections among them are performed, and the final routed wirelength is used as a metric for determining the performance of the design. By minimizing final routed wirelength, power dissipation and interconnect delay can be reduced. ^ The purpose of this Dissertation is to examine the implications of nanometer-scale VLSI technology in the physical design process and to introduce effective approaches to facilitate the overall physical design flow. With this objective, a clustering algorithm, called SafeNet, is developed in the context of VLSI placement, in order to improve both scalability and performance of the placer. The clustering algorithm applies fine clustering of the hypergraphs, thereby preserving the connectivity of the original VLSI circuits and avoiding any significant modification. ^ Moreover, a flat placement algorithm, called PlaceD, is developed as an approach to the wirelength-driven placement problem on application-specific integrated circuits. The algorithm formulates the placement problem as a non-linear constrained optimization problem and applies size scaling in order to minimize the total wire-length of the design, starting with an initial placement obtained using an optimal region-based approach. Simultaneously, the placement algorithm also satisfies various placement constraints. ^ Furthermore, a two-level placement algorithm, called PlaceR, is proposed to address the routability-driven placement problem. This placement algorithm estimates the routed wirelength during global placement using wire density. After the routed wirelength inside multiple regions is estimated, the algorithm incorporates the routability information into an objective function for the global placement in order to guide the placement process. PlaceR also combines a method for the spreading of wire density with clustering, pin congestion control, and size scaling. In this way, the placer minimizes wire congestion and the final routed wirelength of the design. ^ Finally, a post-processing algorithm for placement, called Allagi, is developed to further improve the placement quality. The algorithm formulates the placement problem as a linear program and reduces the total routed wirelength by identifying congested regions in the design. Circuit components that have been placed in the congested areas of the design are relocated to regions that are optimal in terms of minimizing wirelength. ^ The path for the minimization of congestion and improvement in routability is a necessary step for achieving design optimization and enhancing performance. Empirical results show that the proposed methods efficiently reduce the wirelength and improve the routability of the designs. Each of these methods can be incorporated in the overall physical design flow to improve the placement solution and facilitate the operation of a router.^