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A Connectivity-Based Legalization Scheme for Standard Cell Placement

Journal Paper
Antonios N. Dadaliaris, Panagiotis Oikonomou, Maria G. Koziri, Evangelia Nerantzaki, Thanasis Loukopoulos, Georgios I. Stamoulis
Circuits and Systems , 8, 191-201.
Publication year: 2017

Standard cell placement algorithms have been at the forefront of academic research
concerning the physical design stages of VLSI design flows. The penultimate
step of a standard cell placement procedure is legalization. In this step
the manufacturability of the design is directly settled, and the quality of the
solution, in terms of wirelength, congestion, timing and power consumption
is indirectly defined. Since the heavy lifting regarding processing is performed
by global placers, fast legalization solutions are protruded in state-of-the-art
design flows. In this paper we propose and evaluate a legalization scheme that
surpasses in execution speed two of the most widely used legalizers, without
not only corrupting the quality of the final solution in terms of interconnection
wirelength but improving it in the process.

Scheduling Heuristics for Live Video Transcoding on Cloud Edges

Journal Paper
Panagiotis Oikonomou, Maria G. Koziri, Nikos Tziritas, Thanasis Loukopoulos, and XU Cheng-Zhong
COMMUNICATIONS
Publication year: 2017

Efficient video delivery involves the transcoding of the original sequence into various resolutions, bitrates and standards, in order to match viewers’ capabilities. Since video coding and transcoding are computationally demanding, performing a portion of these tasks at the network edges promises to decrease both the workload and network traffic towards the data centers of media providers. Motivated by the increasing popularity of live casting on social media platforms, in this paper we focus on the case of live video transcoding. Specifically, we investigate scheduling heuristics that decide on which jobs should be assigned to an edge mini⁃datacenter and which to a backend datacenter. Through simulation experiments with different QoS requirements we conclude on the best alternative.

Screening for disorders of mathematics via a web application

Conference
Zygouris, N. C., Stamoulis, G. I., Vlachos, F., Vavougios, D., Dadaliaris, A. N., Nerantzaki, E., Oikonomou P & Striftou
IEEE Global Engineering Education Conference (EDUCON)
Publication year: 2017

Dyscalculia is a neurodevelopmental disorder that affects the ability of a child to learn arithmetic. Dyscalculia appears despite normal intelligence, proper schooling, adequate environment, socioeconomic status and motivation. The first aim of the present research protocol was to construct a battery of tests that can be delivered by computer in order to screen children’s arithmetic skills. Our second aim was to develop a web application screener for dyscalculia that assesses children aged from 8–11 years old and that, to the best of our knowledge, does not exist. The hypothesis of the present study was that Greek students that are already diagnosed by paper-and-pencil tests as dyscalculic, will present lower performance and higher time latencies in the tasks of the aforementioned web application screener. A total of sixty, right handed children (30 male and 30 female, age range 8–11 years old) participated in this study. The students with disorders in mathematics (N=30, 15 male and 15 female) had a statement of dyscalculia issued after assessment at a Centre of Diagnosis, Assessment and Support, as required by Greek Law. The comparison group (N=30) was formed by pupils who attended the same classes with dyscalculics, presented typical academic performance according to their teachers’ ratings and had been matched for age and gender with the children with disorder in mathematics. Three tasks were used for evaluating children’s arithmetic ability: a calculation task, a task that evaluated their skills in understanding mathematical terminology, and an arithmetic problem solving task. Statistical analysis revealed that children with dyscalculia had statistically significant lower mean scores of correct answers and larger time latencies in all tasks compared to their average peers that participated in the comparison group. In conclusion, it must be highlighted that the web application screener for dyscalculia used in this study was found to be a feasible instrument for first-pass screening services and referral.

Heuristics to Augment the Performance of Tetris Legalization: Making a Fast but Inferior Method Competitive

Journal Paper
Antonios N Dadaliaris, Panagiotis Oikonomou, Maria G Koziri, Evangelia Nerantzaki, Yannis Hatzaras, Dimitrios Garyfallou, Thanasis Loukopoulos, Georgios I Stamoulis
Journal of Low Power Electronics
Publication year: 2017

As process minimum feature sizes shrink, interconnect capacitance becomes a larger
proportion of the total switched capacitance, thus standard cell and component placement
increasingly affects power consumption. Therefore, minimizing the total interconnect wire
length becomes a power reduction exercise as well. The final step of a standard cell
placement process consists of legalization where the target is to eliminate overlaps as well
as aligning cell positions to eligible rows. The simplest, yet fastest method in the literature

Domocus: Lock free parallel legalization in standard cell placement

Conference
Panagiotis Oikonomou, Maria G Koziri, Antonios N Dadaliaris, Thanasis Loukopoulos, Georgios I Stamoulis
Modern Circuits and Systems Technologies (MOCAST), 2017 6th International Conference on
Publication year: 2017

Abstract: In the cell placement problem a circuit’s cells must be placed within a specified chip
area so that they are row aligned and contain no overlaps. The problem is usually tackled in
phases, whereby in the first phase a global placer performs an initial spreading of cells with
regards to some optimization criterion, most commonly wire length minimization. The output
of the first phase might violate alignment and overlap constraints, therefore in a second
phase, called legalization, the target is to restore constraint violations while incurring

The Implementation of a Web Application for Screening Children with Dyslexia

Book Chapter
Antonios N Dadaliaris, Panagiotis Oikonomou, George I Stamoulis, Denis Vavougios, Evaggelia Nerantzaki, Aikaterini Striftou
Interactive Collaborative Learning: Proceedings of the 19th ICL Conference
Publication year: 2016

Abstract. Developmental dyslexia is defined as an unexpected specific and persistent failure
to acquire efficient reading skills despite conventional instruction, adequate intelligence and
sociocultural opportunity. The main aim of the present research protocol was to construct a
web screening battery of tests in order to screen children’s reading, orthographic and
cognitive skills. The main hypothesis of the present study was that Greek students that were
already diagnosed as dyslexic, shall present significantly lower scores. A total of sixty,

Performance Evaluation of Tetris-based Legalization Heuristics

Conference
Antonios N. Dadaliaris, Evangelia Nerantzaki, Maria G. Koziri, Panagiotis Oikonomou, Thanasis Loukopoulos, and Georgios I. Stamoulis
In Proceedings of the 20th Pan-Hellenic Conference on Informatics (PCI '16). ACM, New York, NY, USA, , Article 60 , 6 pages.
Publication year: 2016

Algorithms for standard cell placement legalization have attracted significant research efforts in the past. A prominent member of this category is the Tetris algorithm which is a simple and particularly fast method for legalizing an initial placement containing overlaps. In the relevant literature sophisticated legalization schemes were proposed using Tetris as a performance yardstick. In order to achieve better performance such schemes usually sacrifice the fast running time of Tetris by a large margin. In this paper we turn our focus on simple Tetris variations that improve performance without seriously compromising running time. Specifically, we present five generic heuristic variations of the initial Tetris algorithm. Through experimental evaluation we conclude on the merits of each approach.

The implementation of a web application for screening children with dyslexia.

Conference
Nikolaos C Zygouris, Filippos Vlachos, Antonios N Dadaliaris, Panagiotis Oikonomou, George I Stamoulis, Denis Vavougios, Evaggelia Nerantzaki, Aikaterini Striftou
Publication year: 2016

Abstract. Developmental dyslexia is defined as an unexpected specific and persistent failure
to acquire efficient reading skills despite conventional instruction, adequate intelligence and
sociocultural opportunity. The main aim of the present research protocol was to construct a
web screening battery of tests in order to screen children’s reading, orthographic and
cognitive skills. The main hypothesis of the present study was that Greek students that were
already diagnosed as dyslexic, shall present significantly lower scores. A total of sixty,

VDA Place+: Voltage-Drop-Aware Placement

Conference
Antonios N Dadaliaris, Panagiotis D Oikonomou, George Dimitriou, Georgios I Stamoulis
Publication year: 2014

Abstract Voltage drop on the power supply network is an issue of ultimate importance in
integrated circuit (IC) fabrication processes as we move beyond the 30nm technology
barrier, affecting both timing and reliability. We propose an evolved variation of our previous
placer that can achieve more balanced results concerning the timing of the critical path and
the total wire-length of a design. The placer works incrementally to existing placers and is,
thus easier to integrate into existing design flows. Keywords: Algorithms, physical design,

Heuristics for Iterative Detailed Standard Cell Placement

Conference
Panagiotis Oikonomou, Maria G Koziri, Antonios N Dadaliaris, Yannis Hatzaras, Evangelia Nerantzaki, Georgios I Stamoulis
Proceedings of the SouthEast European Design Automation, Computer Engineering, Computer Networks and Social Media Conference
Publication year: 2016

Abstract In cell placement a number of cells with rectangular shapes, must be placed inside
a chip area so that no cells overlap and a target function is optimized. In standard cell
placement all rectangles have the same width and the chip area is split into rows of
equivalent width. Cells must be placed inside rows without overlaps and without exceeding
row boundaries. A final solution is obtained using at least two stages. In the first stage, often
called global placement, cells are distributed so as to optimize the target function. This

Enhanced Tetris Legalization

Conference
Antonios N Dadaliaris, Evangelia Nerantzaki, Panagiotis Oikonomou, Yannis Hatzaras, Angeliki-Olympia Troumpoulou, Ioannis Arvanitakis, Georgios I Stamoulis
Proceedings of the SouthEast European Design Automation, Computer Engineering, Computer Networks and Social Media Conference
Publication year: 2016

Abstract Legalization and detailed placement methods for standard cell designs, are two of
the most notable topics in current VLSI research. Being the final steps in a classic placement
procedure they must be efficient in terms of the delay overhead they introduce to the overall
design flow and the quality of the final solution. In this paper we present a combined solution
of the aforementioned steps, based on Tetris a particular simple and fast legalization
algorithm, that produces considerable results taking into account the tradeoff between

Bagged nonlinear hebbian learning algorithm for fuzzy cognitive maps working on classification tasks

Conference
Elpiniki I Papageorgiou, Panagiotis Oikonomou, Arthi Kannappan
Hellenic Conference on Artificial Intelligence
Publication year: 2012

Abstract Learning of fuzzy cognitive maps (FCMs) is one of the most useful characteristics
which have a high impact on modeling and inference capabilities of them. The learning
approaches for FCMs are concentrated on learning the connection matrix, based either on
expert intervention and/or on the available historical data. Most learning approaches for
FCMs are Hebbian-based and evolutionary-based algorithms. A new learning algorithm for
FCMs is proposed in this research work, inheriting the main aspects of the bagging

On formulating and tackling integrated circuit placement as a scheduling problem

Conference
Panagiotis Oikonomou, Thanasis Loukopoulos, Antonios N Dadaliaris, Maria G Koziri, Georgios I Stamoulis
Proceedings of the 19th Panhellenic Conference on Informatics
Publication year: 2015

Abstract Integrated circuit (IC) placement consists of placing the cells of the IC on a chip
plane so that overall performance is optimized. Various performance criteria have been
considered with the most common being wire length. In this paper we tackle the problem
with the optimization goal of reducing end to end delay, also called critical or longest path.
We investigate the case where the chip plane has a priori (before placement)” sweet” spots,
discuss its complexity and show the problem’s relevance to job scheduling. In the …

Particle swarm optimization approach for fuzzy cognitive maps applied to autism classification

Conference
Panagiotis Oikonomou, Elpiniki I Papageorgiou
IFIP International Conference on Artificial Intelligence Applications and Innovations
Publication year: 2013

Abstract The task of classification using intelligent methods and learning algorithms is a
difficult task leading the research community on finding new classifications techniques to
solve it. In this work, a new approach based on particle swarm optimization (PSO) clustering
is proposed to perform the fuzzy cognitive map learning for classification performance. Fuzzy
cognitive map (FCM) is a simple, but also powerful computational intelligent technique
which is used for the adoption of the human knowledge and/or historical data, into a