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fix: fix handling of loop openings for systems that are nonlinear in the inputs #3774

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Merged
merged 2 commits into from
Jul 4, 2025
Merged

fix: fix handling of loop openings for systems that are nonlinear in the inputs #3774

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728055c
fix: fix handling of loop openings for systems that are nonlinear in …
AayushSabharwal Jun 26, 2025
561b14d
fix: make loop opening parameters solvable
AayushSabharwal Jul 4, 2025
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34 changes: 24 additions & 10 deletions src/systems/analysis_points.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -491,14 +491,20 @@ struct Break <: AnalysisPointTransformation
applicable if `add_input == true`.
"""
default_outputs_to_input::Bool
"""
Whether the added input is a parameter. Only applicable if `add_input == true`.
"""
added_input_is_param::Bool
end

"""
$(TYPEDSIGNATURES)

`Break` the given analysis point `ap`.
"""
Break(ap::AnalysisPoint, add_input::Bool = false) = Break(ap, add_input, false)
function Break(ap::AnalysisPoint, add_input::Bool = false, default_outputs_to_input = false)
Break(ap, add_input, default_outputs_to_input, false)
end

function apply_transformation(tf::Break, sys::AbstractSystem)
modify_nested_subsystem(sys, tf.ap) do breaksys
Expand Down Expand Up @@ -528,9 +534,15 @@ function apply_transformation(tf::Break, sys::AbstractSystem)
new_def
end
@set! breaksys.defaults = defs
unks = copy(get_unknowns(breaksys))
push!(unks, new_var)
@set! breaksys.unknowns = unks
if tf.added_input_is_param
ps = copy(get_ps(breaksys))
push!(ps, new_var)
@set! breaksys.ps = ps
else
unks = copy(get_unknowns(breaksys))
push!(unks, new_var)
@set! breaksys.unknowns = unks
end

return breaksys, (new_var,)
end
Expand Down Expand Up @@ -812,12 +824,14 @@ Given a list of analysis points, break the connection for each and set the outpu
"""
function handle_loop_openings(sys::AbstractSystem, aps)
for ap in canonicalize_ap(sys, aps)
sys, (outvar,) = apply_transformation(Break(ap, true, true), sys)
if Symbolics.isarraysymbolic(outvar)
push!(get_eqs(sys), outvar ~ zeros(size(outvar)))
sys, (d_v,) = apply_transformation(Break(ap, true, true, true), sys)
guesses = copy(get_guesses(sys))
guesses[d_v] = if symbolic_type(d_v) == ArraySymbolic()
fill(NaN, size(d_v))
else
push!(get_eqs(sys), outvar ~ 0)
NaN
end
@set! sys.guesses = guesses
end
return sys
end
Expand Down Expand Up @@ -849,10 +863,10 @@ All other keyword arguments are forwarded to `linearization_function`.
"""
function get_linear_analysis_function(
sys::AbstractSystem, transform, aps; system_modifier = identity, loop_openings = [], kwargs...)
sys = handle_loop_openings(sys, loop_openings)
aps = canonicalize_ap(sys, aps)
dus = []
us = []
sys = handle_loop_openings(sys, loop_openings)
aps = canonicalize_ap(sys, aps)
for ap in aps
sys, (du, u) = apply_transformation(transform(ap), sys)
push!(dus, du)
Expand Down
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