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Decouple output scheduling from solver state #191

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d48dcc3
Decouple output from solver state
AhmedSalih3d Jul 8, 2026
d119d33
Stabilize neighbor rebuild state
AhmedSalih3d Jul 8, 2026
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69 changes: 50 additions & 19 deletions src/SPHCellList.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -689,9 +689,17 @@ using TimerOutputs: @timeit
end


# Per-particle local Δx removed: use single scalar `SimMetaData.Δx`.
# Runtime state that must persist across output intervals. Keeping these
# values outside SimulationLoop prevents output scheduling from changing
# neighbor-list rebuilds or adaptive time-step sequencing.
mutable struct SimulationRuntimeState{T}
Δx::T
dt::T
IsInitialized::Bool
end

@inbounds function SimulationLoop(SimDensityDiffusion::SDD, SimViscosity::SV, SimKernel,
Runtime::SimulationRuntimeState{FloatType},
SimMetaData::SimulationMetaData{Dimensions, FloatType, SMode, KMode, BMode, LMode},
SimConstants, SimParticles, FullStencil,
ParticleRanges, UniqueCells, CellListIndices,
Expand All @@ -718,34 +726,38 @@ using TimerOutputs: @timeit

###
UniqueCellsView = view(UniqueCells, 1:SimMetaData.IndexCounter)
# This code here is to initialize the first time step for each simulation loop
dt = SimConstants.CFL * (SimKernel.h / SimConstants.c₀)
dt = Runtime.dt
TimeSteppingMode = SimMetaData.TimeSteppingMode

@no_escape begin
AccelerationMax = @alloc(FloatType, length(SimParticles.Position))
dt₂ = dt * 0.5

SimMetaData.IndexCounter = UpdateNeighbors!(SimParticles, SimKernel.H⁻¹, SortingScratchSpace, ParticleRanges, UniqueCells, CellListIndices)
UniqueCellsView = view(UniqueCells, 1:SimMetaData.IndexCounter)
BuildNeighborCellLists!(NeighborCellLists, FullStencil, UniqueCellsView, ParticleRanges)

if TimeSteppingMode isa SingleNeighborTimeStepping
@timeit SimMetaData.HourGlass "00 Init Pressure" Pressure!(SimParticles.Pressure, SimParticles.Density, SimConstants)
@timeit SimMetaData.HourGlass "00a Init MDBC" ApplyMDBCBeforeHalf!(SimMetaData, SimKernel, SimConstants, SimParticles, ParticleRanges, UniqueCells)
@timeit SimMetaData.HourGlass "00b Init NeighborLoop" NeighborLoopPerParticle!(
SimDensityDiffusion, SimViscosity, SimKernel, SimMetaData,
SimConstants, SimParticles, ParticleRanges, CellListIndices,
NeighborCellLists, dρdtI, SimParticles.Acceleration, ∇Cᵢ, ∇◌rᵢ, AccelerationMax,
)
if !Runtime.IsInitialized
SimMetaData.IndexCounter = UpdateNeighbors!(SimParticles, SimKernel.H⁻¹, SortingScratchSpace, ParticleRanges, UniqueCells, CellListIndices)
UniqueCellsView = view(UniqueCells, 1:SimMetaData.IndexCounter)
BuildNeighborCellLists!(NeighborCellLists, FullStencil, UniqueCellsView, ParticleRanges)
copyto!(Positionₙ⁺, SimParticles.Position)
Runtime.Δx = zero(Runtime.Δx)
Runtime.IsInitialized = true

if TimeSteppingMode isa SingleNeighborTimeStepping
@timeit SimMetaData.HourGlass "00 Init Pressure" Pressure!(SimParticles.Pressure, SimParticles.Density, SimConstants)
@timeit SimMetaData.HourGlass "00a Init MDBC" ApplyMDBCBeforeHalf!(SimMetaData, SimKernel, SimConstants, SimParticles, ParticleRanges, UniqueCells)
@timeit SimMetaData.HourGlass "00b Init NeighborLoop" NeighborLoopPerParticle!(
SimDensityDiffusion, SimViscosity, SimKernel, SimMetaData,
SimConstants, SimParticles, ParticleRanges, CellListIndices,
NeighborCellLists, dρdtI, SimParticles.Acceleration, ∇Cᵢ, ∇◌rᵢ, AccelerationMax,
)
end
end

NextOutputTime = next_output_time(SimMetaData)
while SimMetaData.TotalTime <= NextOutputTime
@timeit SimMetaData.HourGlass "01 Calculate IndexCounter" begin

SimMetaData.Δx = UpdateΔx!(SimMetaData.Δx, Positionₙ⁺, SimParticles.Position)
ShouldRebuild = SimMetaData.Δx >= SimKernel.h
Runtime.Δx = UpdateΔx!(Runtime.Δx, Positionₙ⁺, SimParticles.Position)
ShouldRebuild = Runtime.Δx >= SimKernel.h

# println("Δx: ", Δx, "h: ", SimKernel.h," dt: ", SimMetaData.CurrentTimeStep, " Iteration: ", SimMetaData.Iteration, " TotalTime: ", SimMetaData.TotalTime, " OutputIterationCounter: ", SimMetaData.OutputIterationCounter)

Expand All @@ -757,9 +769,20 @@ using TimerOutputs: @timeit
# if mod(SimMetaData.Iteration, ceil(Int, SimKernel.H / (SimConstants.c₀ * dt * (1/SimConstants.CFL)) )) == 0 || SimMetaData.Iteration == 1
if ShouldRebuild
@timeit SimMetaData.HourGlass "01a Actual Calculate IndexCounter" SimMetaData.IndexCounter = UpdateNeighbors!(SimParticles, SimKernel.H⁻¹, SortingScratchSpace, ParticleRanges, UniqueCells, CellListIndices)
SimMetaData.Δx = zero(eltype(dρdtI))
Runtime.Δx = zero(eltype(dρdtI))
UniqueCellsView = view(UniqueCells, 1:SimMetaData.IndexCounter)
BuildNeighborCellLists!(NeighborCellLists, FullStencil, UniqueCellsView, ParticleRanges)
copyto!(Positionₙ⁺, SimParticles.Position)

if TimeSteppingMode isa SingleNeighborTimeStepping
@timeit SimMetaData.HourGlass "01b Rebuild Pressure" Pressure!(SimParticles.Pressure, SimParticles.Density, SimConstants)
@timeit SimMetaData.HourGlass "01c Rebuild MDBC" ApplyMDBCBeforeHalf!(SimMetaData, SimKernel, SimConstants, SimParticles, ParticleRanges, UniqueCells)
@timeit SimMetaData.HourGlass "01d Rebuild NeighborLoop" NeighborLoopPerParticle!(
SimDensityDiffusion, SimViscosity, SimKernel, SimMetaData,
SimConstants, SimParticles, ParticleRanges, CellListIndices,
NeighborCellLists, dρdtI, SimParticles.Acceleration, ∇Cᵢ, ∇◌rᵢ, AccelerationMax,
)
end
end
end

Expand Down Expand Up @@ -819,7 +842,10 @@ using TimerOutputs: @timeit
@timeit SimMetaData.HourGlass "10 Update MetaData" UpdateMetaData!(SimMetaData, dt)

@timeit SimMetaData.HourGlass "11 Update TimeStep" dt = UpdateTimeStep(AccelerationMax, SimConstants, SimKernel)
dt₂ = dt * 0.5
end

Runtime.dt = dt
end

return nothing
Expand Down Expand Up @@ -913,6 +939,11 @@ using TimerOutputs: @timeit
FullStencil = ConstructStencil(Val(Dimensions))
NeighborCellLists = [Int[] for _ in 1:length(UniqueCells)]
_, SortingScratchSpace = Base.Sort.make_scratch(nothing, eltype(SimParticles), NumberOfPoints)
Runtime = SimulationRuntimeState(
zero(FloatType),
SimConstants.CFL * (SimKernel.h / SimConstants.c₀),
false,
)

output = SetupVTKOutput(SimMetaData, SimParticles, SimKernel, Dimensions)

Expand Down Expand Up @@ -949,7 +980,7 @@ using TimerOutputs: @timeit
@inbounds while true

@timeit SimMetaData.HourGlass "00 SimulationLoop" SimulationLoop(
SimDensityDiffusion, SimViscosity, SimKernel, SimMetaData,
SimDensityDiffusion, SimViscosity, SimKernel, Runtime, SimMetaData,
SimConstants, SimParticles, FullStencil, ParticleRanges,
UniqueCells, CellListIndices, SortingScratchSpace,
NeighborCellLists, dρdtI, Velocityₙ⁺, Positionₙ⁺, ρₙ⁺,
Expand Down
15 changes: 14 additions & 1 deletion src/TimeStepping.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,15 @@ function Δt(max_acceleration, SimulationConstants, SPHKernel)
return CFL * min(dt_speed, dt_force)
end

function Δt(_Position, _Velocity, Acceleration::AbstractVector, SimulationConstants, SPHKernel)
max_acceleration = zero(real(eltype(eltype(Acceleration))))
@inbounds for a in Acceleration
acc_norm = norm(a)
max_acceleration = ifelse(acc_norm > max_acceleration, acc_norm, max_acceleration)
end
return Δt(max_acceleration, SimulationConstants, SPHKernel)
end

"""
UpdateTimeStep(AccelerationMax, SimConstants, SimKernel)

Expand All @@ -57,7 +66,7 @@ end

@inline function next_output_time(times::AbstractVector, SimMetaData)
idx = SimMetaData.OutputIterationCounter
if idx < length(times)
if idx <= length(times)
return times[idx]
else
return SimMetaData.SimulationTime
Expand Down Expand Up @@ -113,6 +122,10 @@ function HalfTimeStep(::SimulationMetaData{Dimensions, FloatType, SMode, KMode,
return nothing
end

function FullTimeStep(SimMetaData::SimulationMetaData, SimKernel, SimConstants, SimParticles, ∇Cᵢ, ∇◌rᵢ, dt)
return FullTimeStep(SimMetaData, SimKernel, SimConstants, SimParticles, SimParticles.Velocity, ∇Cᵢ, ∇◌rᵢ, dt)
end

function FullTimeStep(::SimulationMetaData{D,T,NoShifting,K,B,L}, SimKernel,
SimConstants, SimParticles, Velocityₙ⁺, ∇Cᵢ, ∇◌rᵢ, dt) where {D,T,
K<:KernelOutputMode,
Expand Down