From ae91aa38faf927fb40c14966feba9d887d81c9ef Mon Sep 17 00:00:00 2001
From: Clara Hobbs <clara@clarahobbs.com>
Date: Mon, 12 Dec 2022 09:45:48 -0500
Subject: [PATCH] Add global fair lateness scheduling

---
 docs/src/schedules.md     |  1 +
 src/RealTimeScheduling.jl |  1 +
 src/schedules.jl          | 19 +++++++++++++++++--
 3 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/docs/src/schedules.md b/docs/src/schedules.md
index c784650..b4416e6 100644
--- a/docs/src/schedules.md
+++ b/docs/src/schedules.md
@@ -16,6 +16,7 @@ plot(s, size=(600, 300))
 ```@docs
 schedule_global
 schedule_gedf
+schedule_gfl
 schedule_gfp
 AbstractSchedule
 AbstractTaskSchedule
diff --git a/src/RealTimeScheduling.jl b/src/RealTimeScheduling.jl
index 984b228..c72328b 100644
--- a/src/RealTimeScheduling.jl
+++ b/src/RealTimeScheduling.jl
@@ -44,6 +44,7 @@ export AbstractRealTimeTask,
        schedule_global,
        schedule_gfp,
        schedule_gedf,
+       schedule_gfl,
        # Weakly-hard constraints
        WeaklyHardConstraint,
        MeetAny,
diff --git a/src/schedules.jl b/src/schedules.jl
index 9897d5c..f59b8b8 100644
--- a/src/schedules.jl
+++ b/src/schedules.jl
@@ -219,8 +219,8 @@ end
 Simulate a preemptive global schedule of task system `T` on `m` processors to the specified
 `endtime`.  When releasing a job, the function `release!(job)` is called, allowing
 arbitrary modifications to be made, enabling a wide variety of global schedulers to be
-implemented.  Two common examples are provided: [`schedule_gfp`](@ref) and
-[`schedule_gedf`](@ref).
+implemented.  Three examples are provided: [`schedule_gfp`](@ref), [`schedule_gedf`](@ref),
+and [`schedule_gfl`](@ref).
 
 The `job` provided to `release!(job)` defaults to being released as early as possible (i.e.
 at time 0 or one period after the task's last job), and has the relative deadline and cost
@@ -323,6 +323,21 @@ schedule_gedf(T::AbstractRealTimeTaskSystem, m::Int, time::Real) = schedule_glob
     j.priority = deadline(j)
 end
 
+"""
+    schedule_gfl(T, m, time)
+
+Simulate a preemptive global fair lateness (GFL) schedule of task system `T` on `m`
+processors for the specified `time`.  This provides the lowest tardiness bounds of any
+GEDF-like scheduler under compliant vector analysis; for more information, see Erickson,
+"Managing Tardiness Bounds and Overload in Soft Real-Time Systems."
+DOI: [10.17615/fvp3-q039](https://doi.org/10.17615/fvp3-q039).
+
+See also [`schedule_global`](@ref) for more general global scheduling.
+"""
+schedule_gfl(T::AbstractRealTimeTaskSystem, m::Int, time::Real) = schedule_global(T, m, time) do j
+    j.priority = deadline(j) - (m - 1) / m * cost(j)
+end
+
 @recipe function scheduleplot(sched::RealTimeTaskSchedule)
     endtime = maximum(supremum.(Iterators.flatten(exec.(Iterators.flatten(sched.jobs)))))
     layout --> (length(sched.tasks), 1)