Library prosa.analysis.definitions.readiness

Require Export prosa.behavior.ready.
Require Export prosa.analysis.definitions.schedule_prefix.
Require Export prosa.model.preemption.parameter.
Require Export prosa.model.priority.classes.

Properties of Readiness Models

In this file, we define commonsense properties of readiness models.

Section ReadinessModelProperties.

For any type of jobs with costs and arrival times ...

Context {Job : JobType} `{JobCost Job} `{JobArrival Job}.

... and any kind of processor model, ...

Context {PState: ProcessorState Job}.

... consider a notion of job readiness.

Variable ReadinessModel : JobReady Job PState.

First, we define a notion of non-clairvoyance for readiness models. Intuitively, whether a job is ready or not should depend only on the past (i.e., prior allocation decisions and job behavior), not on future events. Formally, we say that the ReadinessModel is non-clairvoyant if a job's readiness at a given time does not vary across schedules with identical prefixes. That is, given two schedules sched and sched', the predicates job_ready sched j t and job_ready sched' j t may not differ if sched and sched' are identical prior to time t.

  Definition nonclairvoyant_readiness :=
    ∀ sched sched' j h,
      identical_prefix sched sched' h →
      ∀ t,
        t ≤ h →
        job_ready sched j t = job_ready sched' j t.

Next, we relate the readiness model to the preemption model.

Context `{JobPreemptable Job}.

In a preemption-policy-compliant schedule, nonpreemptive jobs must remain scheduled. Further, in a valid schedule, scheduled jobs must be ready. Consequently, in a valid preemption-policy-compliant schedule, a nonpreemptive job must remain ready until at least the end of its nonpreemptive section.

  Definition valid_nonpreemptive_readiness sched :=
     ∀ j t,
        ~~ job_preemptable j (service sched j t) → job_ready sched j t.

End ReadinessModelProperties.