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Changing the grid spacing leads to the error: ERROR: ArgumentError: Equations (1152), states (1140), and initial conditions (1140) are of different lengths. To allow a different number of equations than states use kwarg check_length=false. Stacktrace: from the function discretize.
Expected behavior
PDE system gets discretized as normal and ModelingToolkit.jl can produce a solution.
Minimal Reproducible Example 👇
using OrdinaryDiffEq, ModelingToolkit, MethodOfLines, DomainSets
using LinearAlgebra
# Parameters, variables, and derivatives@parameters t x y
@variablesu(..)
Dt =Differential(t)
Dtt =Differential(t)^2
Dxx =Differential(x)^2
Dyy =Differential(y)^2# 1D PDE and boundary conditionsfunctionsource(t, x, y)
val =sin(10t)
returnifelse(x ==0.5, ifelse(y ==0.5, ifelse(t >0.2, val, 0), 0), 0)
end
eq =Dtt(u(t, x, y)) ~ (Dxx(u(t, x, y)) +Dyy(u(t, x, y))) +source(t, x, y)
bcs = [u(0, x, y) ~0.0,
Dt(u(0, x, y)) ~0.0,
u(t, x, 0) ~0.0,
u(t, 0, y) ~0.0,
u(t, x, 1) ~0.0,
u(t, 1, y) ~0.0]
# Space and time domains
domains = [t ∈Interval(0.0, 2.0),
x ∈Interval(0.0, 1.0),
y ∈Interval(0.0, 1.0),]
# PDE system@named pdesys =PDESystem(eq, bcs, domains, [t, x, y], [u(t, x, y)])
# Method of lines discretization
dx =0.05
order =2
discretization =MOLFiniteDifference([x => dx, y => dx], t, approx_order = order)
# Convert the PDE problem into an ODE problem
prob =discretize(pdesys,discretization)
# Solve ODE problemusing OrdinaryDiffEq
sol =solve(prob, Tsit5())
# Plot results and compare with exact solution
discrete_x = sol[x]
discrete_t = sol[t]
solu = sol[u(t, x, y)]
using Plots
@giffor iframe ineachslice(solu, dims =1)
heatmap(iframe, label="Solution", )#clims=(0.0,0.00250))end
Error & Stacktrace ⚠️
Change dx in the example above to dx = 0.04 and observe the error below.
ERROR: ArgumentError: Equations (1152), states (1140), and initial conditions (1140) are of different lengths. To allow a different number of equations than states use kwarg check_length=false.
Stacktrace:
[1] check_eqs_u0(eqs::Vector{…}, dvs::Vector{…}, u0::Vector{…}; check_length::Bool, kwargs::@Kwargs{…})
@ ModelingToolkit ~/.julia/packages/ModelingToolkit/Gpzyo/src/systems/abstractsystem.jl:1871
[2] process_DEProblem(constructor::Type, sys::ODESystem, u0map::Vector{…}, parammap::SciMLBase.NullParameters; implicit_dae::Bool, du0map::Nothing, version::Nothing, tgrad::Bool, jac::Bool, checkbounds::Bool, sparse::Bool, simplify::Bool, linenumbers::Bool, parallel::Symbolics.SerialForm, eval_expression::Bool, use_union::Bool, tofloat::Bool, symbolic_u0::Bool, u0_constructor::typeof(identity), kwargs::@Kwargs{…})
@ ModelingToolkit ~/.julia/packages/ModelingToolkit/Gpzyo/src/systems/diffeqs/abstractodesystem.jl:837
[3] (ODEProblem{…})(sys::ODESystem, u0map::Vector{…}, tspan::Tuple{…}, parammap::SciMLBase.NullParameters; callback::Nothing, check_length::Bool, kwargs::@Kwargs{})
@ ModelingToolkit ~/.julia/packages/ModelingToolkit/Gpzyo/src/systems/diffeqs/abstractodesystem.jl:936
[4] ODEProblem
@ ModelingToolkit ~/.julia/packages/ModelingToolkit/Gpzyo/src/systems/diffeqs/abstractodesystem.jl:929 [inlined]
[5] (ODEProblem{true, SciMLBase.AutoSpecialize})(sys::ODESystem, u0map::Vector{Pair}, tspan::Tuple{Float64, Float64})
@ ModelingToolkit ~/.julia/packages/ModelingToolkit/Gpzyo/src/systems/diffeqs/abstractodesystem.jl:929
[6] (ODEProblem{true})(::ODESystem, ::Vector{Pair}, ::Vararg{Any}; kwargs::@Kwargs{})
@ ModelingToolkit ~/.julia/packages/ModelingToolkit/Gpzyo/src/systems/diffeqs/abstractodesystem.jl:916
[7] (ODEProblem{true})(::ODESystem, ::Vector{Pair}, ::Vararg{Any})
@ ModelingToolkit ~/.julia/packages/ModelingToolkit/Gpzyo/src/systems/diffeqs/abstractodesystem.jl:915
[8] ODEProblem(::ODESystem, ::Vector{Pair}, ::Vararg{Any}; kwargs::@Kwargs{})
@ ModelingToolkit ~/.julia/packages/ModelingToolkit/Gpzyo/src/systems/diffeqs/abstractodesystem.jl:912
[9] ODEProblem(::ODESystem, ::Vector{Pair}, ::Vararg{Any})
@ ModelingToolkit ~/.julia/packages/ModelingToolkit/Gpzyo/src/systems/diffeqs/abstractodesystem.jl:911
[10] discretize(pdesys::PDESystem, discretization::MOLFiniteDifference{…}; analytic::Nothing, kwargs::@Kwargs{})
@ PDEBase ~/.julia/packages/PDEBase/Aqj4G/src/discretization_state.jl:74
[11] discretize(pdesys::PDESystem, discretization::MOLFiniteDifference{…})
@ PDEBase ~/.julia/packages/PDEBase/Aqj4G/src/discretization_state.jl:55
[12] top-level scope
@ ~/Projects/Toolbox.jl/src/acoustic2D.jl:42
Some type information was truncated. Use `show(err)` to see complete types.
Environment (please complete the following information):
Describe the bug 🐞
Changing the grid spacing leads to the error:
ERROR: ArgumentError: Equations (1152), states (1140), and initial conditions (1140) are of different lengths. To allow a different number of equations than states use kwarg check_length=false. Stacktrace:from the functiondiscretize.Expected behavior
PDE system gets discretized as normal and ModelingToolkit.jl can produce a solution.
Minimal Reproducible Example 👇
Error & Stacktrace⚠️
Change
dxin the example above todx = 0.04and observe the error below.Environment (please complete the following information):
using Pkg; Pkg.status()using Pkg; Pkg.status(; mode = PKGMODE_MANIFEST)versioninfo()The text was updated successfully, but these errors were encountered: