Library rt.implementation.basic.bertogna_fp_example

Require Import rt.util.all.
Require Import rt.model.basic.job rt.model.basic.task
               rt.model.basic.schedule rt.model.basic.schedulability
               rt.model.basic.priority rt.model.basic.platform.
Require Import rt.analysis.basic.workload_bound
Require Import rt.implementation.basic.job
From mathcomp Require Import ssreflect ssrbool ssrnat eqtype seq bigop div.

Module ResponseTimeAnalysisFP.

  Import Job Schedule SporadicTaskset Priority Schedulability Platform InterferenceBoundFP WorkloadBound ResponseTimeIterationFP.
  Import ConcreteJob ConcreteTask ConcreteArrivalSequence ConcreteScheduler.

  (* In this section, we instantiate a simple example to show that the theorems
     contain no contradictory assumptions. *)

  Section ExampleRTA.

    Let tsk1 := {| task_id := 1; task_cost := 2; task_period := 5; task_deadline := 3|}.
    Let tsk2 := {| task_id := 2; task_cost := 4; task_period := 6; task_deadline := 5|}.
    Let tsk3 := {| task_id := 3; task_cost := 3; task_period := 12; task_deadline := 11|}.

    (* Let ts be a task set containing these three tasks (sorted by rate-monotonic priority). *)
    Program Let ts := Build_set [:: tsk1; tsk2; tsk3] _.

    Section FactsAboutTaskset.

      Fact ts_has_valid_parameters:
        valid_sporadic_taskset task_cost task_period task_deadline ts.
        intros tsk IN.
        repeat (move: IN ⇒ /orP [/eqP EQ | IN]; subst; compute); by done.

      Fact ts_has_constrained_deadlines:
          tsk ts
          task_deadline tsk task_period tsk.
        intros tsk IN.
        repeat (move: IN ⇒ /orP [/eqP EQ | IN]; subst; compute); by done.

    End FactsAboutTaskset.

    (* Assume there are two processors. *)
    Let num_cpus := 2.

    (* Recall the FP RTA schedulability test. *)
    Let schedulability_test :=
      fp_schedulable task_cost task_period task_deadline num_cpus.

    (* Now we show that the schedulability test returns true. *)
    Fact schedulability_test_succeeds :
      schedulability_test ts = true.
      unfold schedulability_test, fp_schedulable, fp_claimed_bounds; simpl.
      unfold total_interference_bound_fp, div_floor.
      rewrite big_nil div0n addn0 /=.
      unfold div_floor; simpl.
      set I2 := total_interference_bound_fp task_cost task_period tsk2
                                            [:: (tsk1, 2)].
      assert (H1: I2 4 = 1).
        by unfold I2, total_interference_bound_fp; rewrite big_cons big_nil; compute.
      rewrite H1.
      have H2: 4 + 1 %/ num_cpus = 4 by compute.
      rewrite H2 H1 H2.
      have H3: 3 < 5 by compute.
      rewrite H3.
      unfold fp_bound_of_task.
      have H4: per_task_rta task_cost task_period num_cpus tsk3 [:: (tsk1, 2); (tsk2, 4)]
                            (max_steps task_cost task_deadline tsk3) = 5.
        unfold per_task_rta; simpl.
        unfold total_interference_bound_fp at 9.
        rewrite !big_cons big_nil /=.
        unfold total_interference_bound_fp at 8.
        rewrite !big_cons big_nil /=.
        unfold total_interference_bound_fp at 7.
        rewrite !big_cons big_nil /=.
        unfold total_interference_bound_fp at 6.
        rewrite !big_cons big_nil /=.
        unfold total_interference_bound_fp at 5.
        rewrite !big_cons big_nil /=.
        unfold total_interference_bound_fp at 4.
        rewrite !big_cons big_nil /=.
        unfold total_interference_bound_fp at 3.
        rewrite !big_cons big_nil /=.
        unfold total_interference_bound_fp at 2.
        rewrite !big_cons big_nil /=.
        unfold total_interference_bound_fp at 1.
        by rewrite !big_cons big_nil /=; compute.
      by rewrite H4.

    (* Let arr_seq be the periodic arrival sequence from ts. *)
    Let arr_seq := periodic_arrival_sequence ts.

    (* Assume rate-monotonic priorities. *)
    Let higher_priority : JLDP_policy arr_seq :=
      (FP_to_JLDP job_task (RM task_period)).

    Section FactsAboutPriorityOrder.

      Lemma ts_has_unique_priorities :
        FP_is_antisymmetric_over_task_set (RM task_period) ts.
        unfold RM; intros tsk tsk' IN IN' HP HP'.
        have EQ: task_period tsk = task_period tsk' by apply/eqP; rewrite eqn_leq HP HP'.
        clear HP HP'.
        rewrite !in_cons 2!in_nil 2!orbF in IN IN'; des; rewrite IN IN'; try (by done);
        subst tsk tsk'; simpl in *; by done.

      Lemma priority_is_total :
        FP_is_total_over_task_set (RM task_period) ts.
        unfold RM; intros tsk tsk' IN IN'.
        destruct (leqP (task_period tsk) (task_period tsk'));
          [by left | by right; apply ltnW].

    End FactsAboutPriorityOrder.

    (* Let sched be the work-conserving RM scheduler. *)
    Let sched := scheduler job_cost num_cpus arr_seq higher_priority.

    (* Recall the definition of deadline miss. *)
    Let no_deadline_missed_by :=
      task_misses_no_deadline job_cost job_deadline job_task sched.

    (* Next, we prove that ts is schedulable with the result of the test. *)
    Corollary ts_is_schedulable:
        tsk ts
        no_deadline_missed_by tsk.
      intros tsk IN.
      have VALID := periodic_arrivals_valid_job_parameters ts ts_has_valid_parameters.
      have TSVALID := ts_has_valid_parameters.
      unfold valid_sporadic_job, valid_realtime_job in *; des.
      apply taskset_schedulable_by_fp_rta with (task_cost := task_cost)
       (task_period := task_period) (task_deadline := task_deadline)
       (ts0 := ts) (higher_priority0 := RM task_period); try (by done).
      - by apply ts_has_constrained_deadlines.
      - by apply ts_has_unique_priorities.
      - by apply priority_is_total.
      - by apply RM_is_transitive.
      - by apply periodic_arrivals_all_jobs_from_taskset.
      - by apply periodic_arrivals_are_sporadic.
      - by apply scheduler_jobs_must_arrive_to_execute.
      - apply scheduler_completed_jobs_dont_execute; intro j'.
        -- by specialize (VALID j'); des.
        -- by apply periodic_arrivals_is_a_set.
      - by apply scheduler_sequential_jobs, periodic_arrivals_is_a_set.
      - by apply scheduler_work_conserving.
      - apply scheduler_enforces_policy.
        -- by intros t; apply RM_is_transitive.
          unfold FP_to_JLDP; intros t x y; apply/orP.
          by apply priority_is_total; rewrite periodic_arrivals_all_jobs_from_taskset.
      - by apply schedulability_test_succeeds.

  End ExampleRTA.

End ResponseTimeAnalysisFP.