195348993
A Riemannian Weighted Filter for Edge-sensitive Image Smoothing
14205748
Edge Detection and Anisotropic Diffusion for Tensor-Valued Images
This paper considers feature space of DT-MRI as a differential manifold with an affine-invariant metric, where we generalise Di Zenzo's structure tensor to tensor-valued images for edge detection. To improve the quality of the edges, we smooth out the noise by generalised Perona-Malik method for tensor images. We demonstrate our algorithm on both synthetic and real DT-MRI data.
9404547
Blocking-aware processor voltage scheduling for real-time tasks
As mobile computing is getting popular, there is a growing need for techniques that minimize energy consumption on battery-powered mobile devices. Processor voltage scheduling can effectively reduce processor energy consumption by lowering the processor speed. In this paper, we study voltage scheduling for real-time periodic tasks with non-preemptible sections. Three schemes are proposed: The static speed algorithm derives the minimum static feasible speed based on the stack resource policy. Due to blocking, this static speed is usually higher than the speed required for scheduling fully preemptible tasks (called the utilization speed). Two dynamic speed algorithms are then introduced to further reduce energy consumption. The novel dual speed algorithm operates the processor at the utilization speed whenever possible and switches to the higher static speed only when blocking occurs. The dual speed dynamic reclaiming algorithm reserves time budget for each job, reclaims the unused time budget from completed jobs and redistributes it to subsequent jobs so they can run at a lower speed whenever possible. Feasibility conditions for real-time task sets have been derived and proved mathematically. Simulation results show that the proposed voltage scheduling algorithms dramatically reduce processor energy consumption over non-power-aware scheduling algorithms. Furthermore, the two dynamic speed algorithms consistently outperform the static speed scheme in a wide range of system and workload conditions.
1746401
On the Effective Enumerability of NP Problems
In the field of computational optimization, it is often the case that we are given an instance of an NP problem and asked to enumerate the first few best solutions to the instance. Motivated by this, we propose in this paper a new framework to measure the effective enumerability of NP optimization problems. More specifically, given an instance of an NP problem, we consider the parameterized problem of enumerating a given number of best solutions to the instance, and study its average complexity in terms of the number of solutions. Our framework is different from the previously-proposed ones. For example, although it is known that counting the number of k-paths in a graph is #W[1]-complete, we present a fixed-parameter enumeration algorithm for the problem. We show that most algorithmic techniques for fixed-parameter tractable problems, such as search trees, color coding, and bounded treewidth, can be used for parameterized enumerations. In addition, we design elegant and new enumeration techniques and show how to generate small-size structures and enumerate solutions efficiently.
32440433
The FORTRAN Parallel Transformer and its Programming
The Fortran Parallel Transformer (FPT) is a parallelization tool for Fortran-77 programs. It is used for the automatic parallelization of loops, program transformations, dependence analysis, performance tuning and code generation for various platforms. FPT is able to deal with GOTO's by restructuring ill-structured code using hammock graph transformations. In this way more parallelism becomes detectable. The X-window based Programming Environment, PEFPT, extends FPT with interactive dependence analysis, the iteration space graph, ISG, and guided loop optimization. FPT contains a PVM (Parallel Virtual Machine) code generator which converts the parallel loops into PVM master- and slave-code for a network of workstations. This includes job scheduling, synchronization and optimized data communication. The productivity gained is about a factor of 10 in programming time and a significant speedup of the execution.
204989114
On the numbers of spanning trees and Eulerian tours in generalized de Bruijn graphs
Abstract In this paper, we give the spectra and characteristic polynomials of generalized de Bruijn graphs. By Tutte's Theorem we can obtain the number of spanning trees and the number of Eulerian tours in such graphs.
52810037
A Riemannian Weighted Filter for Edge-sensitive Image Smoothing
This paper describes a new method for image smoothing. We view the image features as residing on a differential manifold, and we work with a representation based on the exponential map for this manifold (i.e. the map from the manifold to a plane that preserves geodesic distances). On the exponential map we characterise the features using a Riemannian weighted mean. We show how both gradient descent and Newton's method can be used to find the mean. Based on this weighted mean, we develop an edge-preserving filter that combines Gaussian and median filters of gray-scale images. We demonstrate our algorithm both on direction fields from shape-from-shading and tensor-valued images