I’ve been trying to understand how to use the Tunable parameter tag, but it seems to include initial conditions when returning a set of parameters as from the example in the ModelingToolkit.jl FAQ page. I’ve included an example below. Am I using this wrong, is there a bug, or am I intended to pass u0 appended to my tunables?
Thanks!
using ModelingToolkit, SciMLStructures, SymbolicIndexingInterface, DifferentialEquations
using SciMLStructures: replace, replace!, Tunable
using ModelingToolkit: t_nounits as t, D_nounits as D
@variables u(t)[1:5]
@parameters k[1:5] [tunable=true]
@parameters c[1:5] [tunable=false]
eqs = [D(u[i])~k[i]*u[i]/c[i] for i in 1:5];
@mtkbuild sys = ODESystem(eqs, t);
u0 = [1.0, 2.0, 3.0, 4.0, 5.0];
odeprob = ODEProblem(sys, [u=>u0], (0, 1), [k => 6*ones(5), c=>7*ones(5)])
@show odeprob.p[1];
newps = 8*ones(5);
currentps = parameter_values(odeprob) # obtain the parameter object from the problem
ps = SciMLStructures.replace(Tunable(), currentps, newps) # create a copy with the tunable values replaced
# remake the problem using the new parameter object
newprob = remake(odeprob, p = ps)
Interestingly, @show odeprob.p[1] returns the following:
odeprob.p[1] = [6.0, 6.0, 6.0, 6.0, 6.0, 1.0, 2.0, 3.0, 4.0, 5.0]
It can be seen from above that the 6.0 values are the tunable parameters, but the vector [1.0, 2.0, 3.0, 4.0, 5.0] appended to those are clearly from the u0 vector also passed in when constructing the ODEProblem.
This difference can also be seen in the currentps and ps lines, where the first element of the tuple is a different length, indicating that u0 is also present when obtaining the parameters that way.
Of course, since the new parameters are of a different length than the old parameters, replace() fails (as expected) and gives the following error:
ERROR: BoundsError: attempt to access 5-element Vector{Float64} at index [6]
Stacktrace:
[1] throw_boundserror(A::Vector{Float64}, I::Tuple{Int64})
@ Base .\essentials.jl:14
[2] getindex
@ .\essentials.jl:916 [inlined]
[3] _ducktyped_parameter_values
@ C:\Users\johnb\.julia\packages\ModelingToolkit\JpO3W\src\systems\parameter_buffer.jl:301 [inlined]
[4] parameter_values
@ C:\Users\johnb\.julia\packages\ModelingToolkit\JpO3W\src\systems\parameter_buffer.jl:296 [inlined]
[5] parameter_values
@ C:\Users\johnb\.julia\packages\SymbolicIndexingInterface\MHJDc\src\value_provider_interface.jl:23 [inlined]
[6] GetParameterIndex
@ C:\Users\johnb\.julia\packages\SymbolicIndexingInterface\MHJDc\src\parameter_indexing.jl:57 [inlined]
[7] AbstractParameterGetIndexer
@ C:\Users\johnb\.julia\packages\SymbolicIndexingInterface\MHJDc\src\value_provider_interface.jl:168 [inlined]
[8] (::SymbolicIndexingInterface.var"#50#51"{…})(g::SymbolicIndexingInterface.GetParameterIndex{…})
@ SymbolicIndexingInterface C:\Users\johnb\.julia\packages\SymbolicIndexingInterface\MHJDc\src\state_indexing.jl:214
[9] iterate
@ .\generator.jl:48 [inlined]
[10] collect_to!(dest::Vector{…}, itr::Base.Generator{…}, offs::Int64, st::Int64)
@ Base .\array.jl:849
[11] collect_to!(dest::Vector{…}, itr::Base.Generator{…}, offs::Int64, st::Int64)
@ Base .\array.jl:857
[12] collect_to_with_first!(dest::Vector{…}, v1::Float64, itr::Base.Generator{…}, st::Int64)
@ Base .\array.jl:827
[13] _collect(c::Vector{…}, itr::Base.Generator{…}, ::Base.EltypeUnknown, isz::Base.HasShape{…})
@ Base .\array.jl:821
[14] collect_similar
@ .\array.jl:720 [inlined]
[15] map
@ .\abstractarray.jl:3371 [inlined]
[16] MultipleGetters
@ C:\Users\johnb\.julia\packages\SymbolicIndexingInterface\MHJDc\src\state_indexing.jl:214 [inlined]
[17] MultipleGetters
@ C:\Users\johnb\.julia\packages\SymbolicIndexingInterface\MHJDc\src\state_indexing.jl:191 [inlined]
[18] (::SymbolicIndexingInterface.MultipleGetters{…})(prob::ProblemState{…})
@ SymbolicIndexingInterface C:\Users\johnb\.julia\packages\SymbolicIndexingInterface\MHJDc\src\value_provider_interface.jl:166
[19] (::ModelingToolkit.ReconstructInitializeprob)(srcvalp::ProblemState{…}, dstvalp::NonlinearProblem{…})
@ ModelingToolkit C:\Users\johnb\.julia\packages\ModelingToolkit\JpO3W\src\systems\nonlinear\initializesystem.jl:321
[20] remake_initialization_data(sys::ODESystem, odefn::Function, u0::Missing, t0::Int64, p::MTKParameters{…}, newu0::Vector{…}, newp::MTKParameters{…})
@ ModelingToolkit C:\Users\johnb\.julia\packages\ModelingToolkit\JpO3W\src\systems\nonlinear\initializesystem.jl:424
[21] remake(prob::ODEProblem{…}; f::Missing, u0::Missing, tspan::Missing, p::MTKParameters{…}, kwargs::Missing, interpret_symbolicmap::Bool, build_initializeprob::Bool, use_defaults::Bool, lazy_initialization::Nothing, _kwargs::@Kwargs{})
@ SciMLBase C:\Users\johnb\.julia\packages\SciMLBase\YTOjh\src\remake.jl:227
[22] top-level scope
@ tunable_testing.jl:23
Some type information was truncated. Use `show(err)` to see complete types.