422 research outputs found
New protocols for the election of a leader in a ring
AbstractIn this paper we investigate the impact of time for the election of a leader in a distributed environment. We propose a new protocol schema that can be specialized to obtain several protocols with different communication-time characteristics when the network is ring-shaped and the communications between processors are synchronous
Algorithms for Hierarchical and Semi-Partitioned Parallel Scheduling
We propose a model for scheduling jobs in a parallel machine setting that takes into account the cost of migrations by assuming that the processing time of a job may depend on the specific set of machines among which the job is migrated. For the makespan minimization objective, the model generalizes classical scheduling problems such as unrelated parallel machine scheduling, as well as novel ones such as semi-partitioned and clustered scheduling. In the case of a hierarchical family of machines, we derive a compact integer linear programming formulation of the problem and leverage its fractional relaxation to obtain a polynomial-time 2-approximation algorithm. Extensions that incorporate memory capacity constraints are also discussed
Feasibility Tests for Recurrent Real-Time Tasks in the Sporadic DAG Model
A model has been proposed in [Baruah et al., in Proceedings of the IEEE
Real-Time Systems Symposium 2012] for representing recurrent
precedence-constrained tasks to be executed on multiprocessor platforms, where
each recurrent task is modeled by a directed acyclic graph (DAG), a period, and
a relative deadline. Each vertex of the DAG represents a sequential job, while
the edges of the DAG represent precedence constraints between these jobs. All
the jobs of the DAG are released simultaneously and have to be completed within
some specified relative deadline. The task may release jobs in this manner an
unbounded number of times, with successive releases occurring at least the
specified period apart. The feasibility problem is to determine whether such a
recurrent task can be scheduled to always meet all deadlines on a specified
number of dedicated processors.
The case of a single task has been considered in [Baruah et al., 2012]. The
main contribution of this paper is to consider the case of multiple tasks. We
show that EDF has a speedup bound of 2-1/m, where m is the number of
processors. Moreover, we present polynomial and pseudopolynomial schedulability
tests, of differing effectiveness, for determining whether a set of sporadic
DAG tasks can be scheduled by EDF to meet all deadlines on a specified number
of processors
Feasibility Analysis of Conditional DAG Tasks
Feasibility analysis for Conditional DAG tasks (C-DAGs) upon multiprocessor platforms is shown to be complete for the complexity class pspace. It is shown that as a consequence integer linear programming solvers (ILP solvers) are likely to prove inadequate for such analysis. A demarcation is identified between the feasibility-analysis problems on C-DAGs that are efficiently solvable using ILP solvers and those that are not, by characterizing a restricted class of C-DAGs for which feasibility analysis is shown to be efficiently solvable using ILP solvers
ILP-based approaches to partitioning recurrent workloads upon heterogeneous multiprocessors
The problem of partitioning systems of independent constrained-deadline sporadic tasks upon heterogeneous multiprocessor platforms is considered. Several different integer linear program (ILP) formulations of this problem, offering different tradeoffs between effectiveness (as quantified by speedup bound) and running time efficiency, are presented
Comparison of methods for logic-query implementation
AbstractA logic query Q is a triple < G, LP, D, where G is the query goal, LP is a logic program without function symbols, and D is a set of facts, possibly stored as tuples of a relational database. The answers of Q are all facts that can be inferred from LP ∪ D and unify with G. A logic query is bound if some argument of the query goal is a constant; it is canonical strongly linear (a CSL query) if LP contains exactly one recursive rule and this rule is linear, i.e., only one recursive predicate occurs in its body. In this paper, the problem of finding the answers of a bound CSL query is studied with the aim of comparing for efficiency some well-known methods for implementing logic queries: the eager method, the counting method, and the magic-set method. It is shown that the above methods can be expressed as algorithms for finding particular paths in a directed graph associated to the query. Within this graphical formalism, a worst-case complexity analysis of the three methods is performed. It turns out that the counting method has the best upper bound for noncyclic queries. On the other hand, since the counting method is not safe if queries are cyclic, the method is extended to safely implement this kind of queries as well
Proceedings of the 12th workshop on models and algorithms for planning and scheduling problems
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