We show that certain twisting deformations of a family of supersolvable groups are simple as Hopf algebras. These groups are direct products of two generalized dihedral groups. Examples of this construction arise in dimensions 60 and pq, for prime numbers p, q with q|p − 1. We also show that certain twisting deformation of the symmetric group is simple as a Hopf algebra. On the other hand, we p...

Priority queues and double-ended priority queues are fundamental data types in Computer Science, and various data structures have been proposed to implement them. In particular, diamond deques, interval heaps, min-max-pair heaps, and twin-heaps provide implicit structures for double-ended priority queues. Although these heap-like structures are essentially the same when they are presented in an...

In this paper we show that the widely used normalization constraint ∑ n i=1 wi = 1 does not apply to the priority vectors associated with reciprocal relations, whenever additive transitivity is involved. We show that misleading applications of this type of normalization may lead to unsatisfactory results and we give some examples from the literature. Then, we propose an alternative normalizatio...

In this paper we show how to implement bounded ordered dictionaries, also called bounded priority queues, in O(log log N) time per operation and O(n) space. Here n denotes the number of elements stored in the dictionary and N denotes the size of the universe. Previously, this time bound required O(N) space E77].

A k-bounded priority queue transforms an input sequence CT into an output sequence z which is a re-ordering of the sequence c while never storing more than k elements during the transformation. We consider the set of all such related pairs (a, 7) in both the case that cs is a binary sequence and the case that o is a permutation of 1,2,. , n. We derive properties of this relation and use it to d...

Well-known results on the ergodicity of queues with preemptive priority were obtained under assumption that jobs arrive according to Poisson process. This assumption, however, does not always hold true in practice. In our work we find sufficient conditions for two classes a single server, where interarrival times high-priority have either Erlang or hyperexponential distribution and low-priority...

Structuring real-time concurrent programs in the form of groups of fixed-priority processes is an old art which is appropriate for only a small fraction of modern real-time distributed computing application systems. However, it is still practiced on the basis of an insufficient technical foundation. One of the basic issues in using the fixed-priority process structuring approach is to avoid the...

The contributions of this paper are threefold. First, a solution to the problem of prioritized mutual exclusion in a distributed system is proved correct. This protocol is based on fewer requirements than prioritized extensions of other protocols and outperforms other protocols with an average complexity of (log n) and a worst-case complexity of O(n) messages for n nodes. Second, the concept of...

Real-Time Mach provides real-time thread and real-time synchronization facilities. A real-time thread can be created for a periodic or aperiodic activity with a timing constraint. Threads can be synchronized among them using a real-time version of the monitor based synchronization mechanism with a suitable locking protocol. In Real-Time Mach, we have implemented several locking policies, such a...

In recent years, real-time operating systems began to support the resource reservation paradigm. This technique has proved to be very effective in providing QoS to both, real-time and legacy applications, ensuring that the temporal misbehavior of an application does not affect any other (temporal isolation). However, resource sharing in a reservation system is still not well understood, and can...