Merge pull request #645 from AayushSabharwal/as/discrete-save

feat: add discrete saving feature to ODESolution

Project.toml

@@ -12,6 +12,7 @@ ConstructionBase = "187b0558-2788-49d3-abe0-74a17ed4e7c9"
 Distributed = "8ba89e20-285c-5b6f-9357-94700520ee1b"
 DocStringExtensions = "ffbed154-4ef7-542d-bbb7-c09d3a79fcae"
 EnumX = "4e289a0a-7415-4d19-859d-a7e5c4648b56"
+Expronicon = "6b7a57c9-7cc1-4fdf-b7f5-e857abae3636"
 FunctionWrappersWrappers = "77dc65aa-8811-40c2-897b-53d922fa7daf"
 IteratorInterfaceExtensions = "82899510-4779-5014-852e-03e436cf321d"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
@@ -62,6 +63,7 @@ DataFrames = "1.6"
 Distributed = "1.10"
 DocStringExtensions = "0.9"
 EnumX = "1"
+Expronicon = "0.8"
 ForwardDiff = "0.10.36"
 FunctionWrappersWrappers = "0.1.3"
 IteratorInterfaceExtensions = "^1"
@@ -78,7 +80,7 @@ PyCall = "1.96"
 PythonCall = "0.9.15"
 RCall = "0.14.0"
 RecipesBase = "1.3.4"
-RecursiveArrayTools = "3.22.0"
+RecursiveArrayTools = "3.26.0"
 Reexport = "1"
 RuntimeGeneratedFunctions = "0.5.12"
 SciMLOperators = "0.3.7"
@@ -87,7 +89,7 @@ StableRNGs = "1.0"
 StaticArrays = "1.7"
 StaticArraysCore = "1.4"
 Statistics = "1.10"
-SymbolicIndexingInterface = "0.3.20"
+SymbolicIndexingInterface = "0.3.26"
 Tables = "1.11"
 Zygote = "0.6.67"
 julia = "1.10"

ext/SciMLBaseZygoteExt.jl

@@ -33,7 +33,7 @@ import SciMLStructures
             N = length((size(dprob.u0)..., length(du)))
         end
         Δ′ = ODESolution{T, N}(du, nothing, nothing,
-            VA.t, VA.k, dprob, VA.alg, VA.interp, VA.dense, 0, VA.stats,
+            VA.t, VA.k, VA.discretes, dprob, VA.alg, VA.interp, VA.dense, 0, VA.stats,
             VA.alg_choice, VA.retcode)
         (Δ′, nothing, nothing)
     end
@@ -60,7 +60,7 @@ end
         T = eltype(eltype(VA.u))
         N = ndims(VA)
         Δ′ = ODESolution{T, N}(du, nothing, nothing,
-            VA.t, VA.k, dprob, VA.alg, VA.interp, VA.dense, 0, VA.stats,
+            VA.t, VA.k, VA.discretes, dprob, VA.alg, VA.interp, VA.dense, 0, VA.stats,
             VA.alg_choice, VA.retcode)
         (Δ′, nothing, nothing)
     end
@@ -117,9 +117,11 @@ end
         elseif i === nothing
             throw(error("Zygote AD of purely-symbolic slicing for observed quantities is not yet supported. Work around this by using `A[sym,i]` to access each element sequentially in the function being differentiated."))
         else
-            Δ′ = [[i == k ? Δ[j] : zero(x[1]) for k in 1:length(x)]
-                  for (x, j) in zip(VA.u, 1:length(VA))]
-            (Δ′, nothing)
+            VA = recursivecopy(VA)
+            recursivefill!(VA, zero(eltype(VA)))
+            v = view(VA, i, ntuple(_ -> :, ndims(VA) - 1)...)
+            copyto!(v, Δ)
+            (VA, nothing)
         end
     end
     VA[sym], ODESolution_getindex_pullback
@@ -172,15 +174,15 @@ end
     VA[sym], ODESolution_getindex_pullback
 end
 
-@adjoint function ODESolution{T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14
-}(u,
+@adjoint function ODESolution{T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13
+, T14, T15}(u,
         args...) where {T1, T2, T3, T4, T5, T6, T7, T8,
-        T9, T10, T11, T12, T13, T14}
+        T9, T10, T11, T12, T13, T14, T15}
     function ODESolutionAdjoint(ȳ)
         (ȳ, ntuple(_ -> nothing, length(args))...)
     end
 
-    ODESolution{T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14}(u, args...),
+    ODESolution{T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15}(u, args...),
     ODESolutionAdjoint
 end
 

src/SciMLBase.jl

@@ -23,6 +23,7 @@ import RuntimeGeneratedFunctions
 import EnumX
 import ADTypes: AbstractADType
 import Accessors: @set, @reset
+using Expronicon.ADT: @match
 
 using Reexport
 using SciMLOperators
@@ -717,6 +718,7 @@ include("problems/problem_traits.jl")
 include("problems/problem_interface.jl")
 include("problems/optimization_problems.jl")
 
+include("clock.jl")
 include("solutions/basic_solutions.jl")
 include("solutions/nonlinear_solutions.jl")
 include("solutions/ode_solutions.jl")
@@ -835,4 +837,6 @@ export step!, deleteat!, addat!, get_tmp_cache,
 
 export ContinuousCallback, DiscreteCallback, CallbackSet, VectorContinuousCallback
 
+export Clocks, TimeDomain, is_discrete_time_domain, isclock, issolverstepclock, iscontinuous
+
 end

src/clock.jl

@@ -0,0 +1,92 @@
+module Clocks
+
+export TimeDomain
+
+using Expronicon.ADT: @adt, @match
+
+@adt TimeDomain begin
+    Continuous
+    struct PeriodicClock
+        dt::Union{Nothing, Float64, Rational{Int}}
+        phase::Float64 = 0.0
+    end
+    SolverStepClock
+end
+
+Base.Broadcast.broadcastable(d::TimeDomain) = Ref(d)
+
+end
+
+using .Clocks
+
+"""
+    Clock(dt)
+    Clock()
+
+The default periodic clock with tick interval `dt`. If `dt` is left unspecified, it will
+be inferred (if possible).
+"""
+Clock(dt::Union{<:Rational, Float64}; phase = 0.0) = PeriodicClock(dt, phase)
+Clock(dt; phase = 0.0) = PeriodicClock(convert(Float64, dt), phase)
+Clock(; phase = 0.0) = PeriodicClock(nothing, phase)
+
+@doc """
+    SolverStepClock
+
+A clock that ticks at each solver step (sometimes referred to as "continuous sample time").
+This clock **does generally not have equidistant tick intervals**, instead, the tick
+interval depends on the adaptive step-size selection of the continuous solver, as well as
+any continuous event handling. If adaptivity of the solver is turned off and there are no
+continuous events, the tick interval will be given by the fixed solver time step `dt`.
+
+Due to possibly non-equidistant tick intervals, this clock should typically not be used with
+discrete-time systems that assume a fixed sample time, such as PID controllers and digital
+filters.
+""" SolverStepClock
+
+isclock(c) = @match c begin
+    PeriodicClock(_...) => true
+    _ => false
+end
+
+issolverstepclock(c) = @match c begin
+    &SolverStepClock => true
+    _ => false
+end
+
+iscontinuous(c) = @match c begin
+    &Continuous => true
+    _ => false
+end
+
+is_discrete_time_domain(c) = !iscontinuous(c)
+
+function first_clock_tick_time(c, t0)
+    @match c begin
+        PeriodicClock(dt, _...) => ceil(t0 / dt) * dt
+        &SolverStepClock => t0
+        &Continuous => error("Continuous is not a discrete clock")
+    end
+end
+
+struct IndexedClock{I}
+    clock::TimeDomain
+    idx::I
+end
+
+Base.getindex(c::TimeDomain, idx) = IndexedClock(c, idx)
+
+function canonicalize_indexed_clock(ic::IndexedClock, sol::AbstractTimeseriesSolution)
+    c = ic.clock
+
+    return @match c begin
+        PeriodicClock(dt, _...) => ceil(sol.prob.tspan[1] / dt) * dt .+ (ic.idx .- 1) .* dt
+        &SolverStepClock => begin
+            ssc_idx = findfirst(eachindex(sol.discretes)) do i
+                !isa(sol.discretes[i].t, AbstractRange)
+            end
+            sol.discretes[ssc_idx].t[ic.idx]
+        end
+        &Continuous => sol.t[ic.idx]
+    end
+end

src/remake.jl

@@ -475,6 +475,10 @@ end
 anydict(d) = Dict{Any, Any}(d)
 anydict() = Dict{Any, Any}()
 
+function _updated_u0_p_internal(
+    prob, ::Missing, ::Missing; interpret_symbolicmap = true, use_defaults = false)
+    return state_values(prob), parameter_values(prob)
+end
 function _updated_u0_p_internal(
         prob, ::Missing, p; interpret_symbolicmap = true, use_defaults = false)
     u0 = state_values(prob)