5,781 research outputs found
An effective two-stage simulated annealing algorithm for the minimum linear arrangement problem
In this paper, an improved two-stage simulated annealing algorithm is presented for the minimum linear arrangement problem for graphs. This algorithm integrates several distinguished features including an efficient heuristic to generate good quality initial solutions, a highly discriminating evaluation function, a special neighborhood function and an effective cooling schedule. The algorithm is evaluated on a set of 30 well-known benchmark instances of the literature and compared with several state-of-the-art algorithms, showing improvements of 17 previous best results
Placement driven retiming with a coupled edge timing model
Retiming is a widely investigated technique for performance optimization. It performs powerful modifications on a circuit netlist. However, often it is not clear, whether the predicted performance improvement will still be valid after placement has been performed. This paper presents a new retiming algorithm using a highly accurate timing model taking into account the effect of retiming on capacitive loads of single wires as well as fanout systems. We propose the integration of retiming into a timing-driven standard cell placement environment based on simulated annealing. Retiming is used as an optimization technique throughout the whole placement process. The experimental results show the benefit of the proposed approach. In comparison with the conventional design flow based on standard FEAS our approach achieved an improvement in cycle time of up to 34% and 17% on the average
Consensus clustering and functional interpretation of gene-expression data
Microarray analysis using clustering algorithms can suffer from lack of inter-method consistency in assigning related gene-expression profiles to clusters. Obtaining a consensus set of clusters from a number of clustering methods should improve confidence in gene-expression analysis. Here we introduce consensus clustering, which provides such an advantage. When coupled with a statistically based gene functional analysis, our method allowed the identification of novel genes regulated by NFκB and the unfolded protein response in certain B-cell lymphomas
Stochastic axial compressor variable geometry schedule optimisation
The design of axial compressors is dictated by the maximisation of flow
efficiency at on design conditions whereas at part speed the requirement for
operation stability prevails. Among other stability aids, compressor variable
geometry is employed to rise the surge line for the provision of an adequate
surge margin. The schedule of the variable vanes is in turn typically obtained
from expensive and time consuming rig tests that go through a vast combination
of possible settings. The present paper explores the suitability of stochastic
approaches to derive the most flow efficient schedule of an axial compressor for
a minimum variable user defined value of the surge margin. A genetic algorithm
has been purposely developed and its satisfactory performance validated against
four representative benchmark functions. The work carries on with the necessary
thorough investigation of the impact of the different genetic operators employed
on the ability of the algorithm to find the global extremities in an effective
and efficient manner. This deems fundamental to guarantee that the algorithm is
not trapped in local extremities. The algorithm is then coupled with a
compressor performance prediction tool that evaluates each individual's
performance through a user defined fitness function. The most flow efficient
schedule that conforms to a prescribed surge margin can be obtained thereby fast
and inexpensively. Results are produced for a modern eight stage high bypass
ratio compressor and compared with experimental data available to the research.
The study concludes with the analysis of the existent relationship between surge
margin and flow efficiency for the particular compressor under scrutiny. The
study concludes with the analysis of the existent relationship between surge
margin and flow efficiency for the particular compressor under scrutiny
- …