Non-trivial Relationships Research Articles

Partially clairvoyant scheduling for aggregate constraints

The problem of partially clairvoyant scheduling is concerned with checking whether an ordered set of jobs, having nonconstant execution times and subject to a collection of imposed constraints, has a partially clairvoyant schedule. Variability of execution times of jobs and nontrivial relationships constraining their executions, are typical features of real-time systems. A partially clairvoyant scheduler parameterizes the schedule, in that the start time of a job in a sequence can depend upon the execution times of jobs that precede it, in the sequence. In real-time scheduling, parameterization of the schedule plays an important role in extending the flexibility of the scheduler, particularly in the presence of variable execution times. It has been shown that the existence of partially clairvoyant schedules can be determined in polynomial time, when the constraints are restricted to be “standard,” that is, relative timing constraints. In this paper, we extend the class of constraints for which partially clairvoyant schedules can be determined efficiently, to include aggregate constraints. Aggregate constraints form a strict superset of standard constraints and can be used to model performance metrics.

The Hypothesis of Charge Independence for Nuclear Phenomena

The hypothesis of charge independence for nuclear phenomena is a symmetry condition which leads to nontrivial relationships to be satisfied by an extensive class of meson-nucleon interactions. Application of the principle to meson production by nucleon collisions and by photons and to meson scattering leads to a number of sensitive tests of the hypothesis. No contradictions are found from the present rather limited experimental data. Extension of the principle to heavy unstable particles (such as $V$-particles) is discussed.