19682410
An Efficient Online Algorithm for Square Detection
A square is a string of characters that can be divided into two identical substrings. The problem of detecting squares in a string finds applications in many areas such as bioinformatics and data compression. In this paper, we give the first efficient online algorithm for the problem. Given any input string, our algorithm reports the first square in the string using O(nlog2 n) time where n is the position in the string where the square ends. This time complexity is only a factor of O(log n) larger than that of an optimal offline algorithm.
7886387
An Efficient Reduction from Constrained to Unconstrained Maximum Agreement Subtree
We propose and study the Maximum Constrained Agreement Subtree (MCAST) problem, which is a variant of the classical Maximum Agreement Subtree (MAST) problem. Our problem allows users to apply their domain knowledge to control the construction of the agreement subtrees in order to get better results. We show that the MCAST problem can be reduced to the MAST problem efficiently and thus we have algorithms for MCAST with running times matching the fastest known algorithms for MAST.
43554221
Online and Dynamic Recognition of Squarefree Strings
The online squarefree recognition problem is to detect the first occurrence of a square in a string whose characters are provided as input one at a time. We present an efficient algorithm to solve this problem for strings over arbitrarily ordered alphabets. Its running time is O(n log n), where n is the ending position of the first square, which matches the running times of the fastest known algorithms for the analogous offline problem. We also present a very simple algorithm for a dynamic version of the problem over general alphabets in which we are initially given a squarefree string, followed by a series of updates, and the objective is to determine after each update if the resulting string contains a square and if so, report it and stop.
43458709
Algorithms for Local Forest Similarity
An ordered labeled tree is a rooted tree, where the left-to-right order among siblings is significant and each node associates a label. A forest is a sequence of ordered labeled trees. Suppose F is a forest. A substructure is a connected subgraph of F. Define a subforest as a sequence of substructures of F such that their roots are siblings. The local forest similarity problem for forests F and G is to find two most similar subforests of F and G. We answer an open problem in Paper [3], and provide efficient algorithms on it. Comparing with previous results, our algorithms achieve better performance.
46430059
An O(n log n)-Time Algorithm for the Maximum Constrained Agreement Subtree Problem for Binary Trees
This paper introduces the maximum constrained agreement subtree problem, which is a generalization of the classical maximum agreement subtree problem This new problem is motivated by the understood constraint when we compare the evolutionary trees We give an O(n log n)-time algorithm for solving the problem when the input trees are binary The time complexity of our algorithm matches the fastest known algorithm for the maximum agreement subtree problem for binary trees.
36553676
Time and Space Efficient Algorithms for Constrained Sequence Alignment
In this paper, we study the constrained sequence alignment problem, which is a generalization of the classical sequence alignment problem with the additional constraint that some characters in the alignment must be positioned at the same columns. The problem finds important applications in Bioinformatics. Our major result is an O(ln2)-time and O(ln)-space algorithm for constructing an optimal constrained alignment of two sequences where n is the length of the longer sequence and l is the length of the constraint. Our algorithm matches the best known time complexity and reduces the best known space complexity by a factor of n for solving the problem. We also apply our technique to design time and space efficient heuristic and approximation algorithm for aligning multiple sequences.
7206861
Defect-aware SOC test scheduling
In this paper we address the test scheduling problem for system-on-chip designs. Different from previous approaches where it is assumed that all tests are performed until completion, we consider the cases where the test process are terminated as soon as a defect is detected. This is common practice in production test of chips. The proposed technique takes into account the probability of defect-detection by a test in order to schedule the tests so that the expected total test time is minimized. We investigate different test bus structures, test scheduling strategies (sequential scheduling vs. concurrent scheduling), and test set assumptions (fixed test time vs. flexible test time). We have also made experiments to illustrate the efficiency of taking defect probability into account during test scheduling.
10777322
Overhead-conscious voltage selection for dynamic and leakage energy reduction of time-constrained systems
Dynamic voltage scaling and adaptive body biasing have been shown to reduce dynamic and leakage power consumption effectively. In this paper, we optimally solve the combined supply voltage and body bias selection problem for multi-processor systems with imposed time constraints, explicitly taking into account the transition overheads implied by changing voltage levels. Both energy and time overheads are considered. We investigate the continuous voltage scaling as well as its discrete counterpart, and we prove NP-hardness in the discrete case. Furthermore, the continuous voltage scaling problem is formulated and solved using nonlinear programming with polynomial time complexity, while for the discrete problem we use mixed integer linear programming. Extensive experiments, conducted on several benchmarks and a real-life example, are used to validate the approaches.
40452783
A Buffering/Caching Mechanism for Continous Media Players
In order to reduce the playback discontinuity of a stream of data (audio for example) sent through a packet-switched network, we proposed a buffering/caching mechanism for continuous media players. The stream playback is usually implemented by two parallel processes: receiving and playing. The former receives stream chips from the network while the latter plays the received stream chips and then empties their occupied buffers for the former. Our buffering/caching mechanism makes the receiving process completely independent of the playing process. Thus, the receiving process does not need to wait for the playing process to empty buffers so that the network bandwidth can be used as much as possible. Because the cached stream chips can be played from the local disk, the response latency of the playback control operations such as REPLAY and REWIND can be reduced as well. The mechanism was developed for our hyper audio web system.
9707498
Efficient test solutions for core-based designs
A test solution for a complex system requires the design of a test access mechanism (TAM), which is used for the test data transportation, and a test schedule of the test data transportation on the designed TAM. An extensive TAM will lead to lower test-application time at the expense of higher routing costs, compared to a simple TAM with low routing cost but long testing time. It is also possible to reduce the testing time of a testable unit by loading the test vectors in parallel, thus increasing the parallelization of a test. However, such a test-time reduction often leads to higher power consumption, which must be kept under control since exceeding the power budget could damage the system under test. Furthermore, the execution of a test requires resources and concurrent execution of tests may not be possible due to resource or other conflicts. In this paper, we propose an integrated technique for test scheduling, test parallelization, and TAM design, where the test application time and the TAM routing are minimized, while considering test conflicts and power constraints. The main features of our technique are the efficiency in terms of computation time and the flexibility to model the system's test behavior, as well as the support for the testing of interconnections, unwrapped cores and user-defined logic. We have implemented our approach and made several experiments on benchmarks as well as industrial designs in order to demonstrate that our approach produces high-quality solution at low computational cost.
1176441
Secure Audit Logging with Tamper-Resistant Hardware
Secure perimeter schemes (e.g. DRM) and tracing traitor schemes (e.g. watermarking, audit logging) strive to mitigate the problems of content escaping the control of the rights holder. Secure audit logging records the user's actions on content and enables detection of some forms of tampering with the logs. We implement Schneier and Kelsey's secure audit logging protocol, strengthening the protocol by using tamper-resistant hardware (an iButton) in two ways: Firstly our implementation of the protocol works offline as well as online. Secondly, we use unforgeable time stamps to increase the possibilities of fraud detection. We provide a performance assessment of our implementation to show under which circumstances the protocol is practical to use.