Apply start values only when warm start is enabled - #329
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Branch variables (PhaseShifterAngle, TapRatioVariable, CosineApproximation), bus voltages (ACP, ACR/IVR, LPAC) and RegulatedVoltageMagnitude got start values even with `warm_start = false`. A partial MIP start makes Gurobi complete it before presolve, which cost 29 minutes on a nodal day-ahead model. Bus voltage and thermal commitment variables now use IOM's `add_variables!` with per-bus hooks and `skip_variable` for must-run units. The reduction-aware branch and regulated-voltage builders keep their own loops and set start values through `set_start_value!`. `test_warm_start.jl` builds each affected model with warm start off and on. Sources IOM from the `mb/warm-start-bug` branch until the IOM change merges.
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luke-kiernan
approved these changes
Sep 28, 2026
| #! format: off | ||
| # bus voltage limits are already per-unit | ||
| get_variable_binary(::Type{VoltageMagnitude}, ::Type{PSY.ACBus}, ::Type{ACPNetworkModel}) = false | ||
| get_variable_lower_bound(::Type{VoltageMagnitude}, bus::PSY.ACBus, ::Type{ACPNetworkModel}) = PSY.get_voltage_limits(bus).min |
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Huh. it's a little odd the get_voltage_limits(bus) runs: I'd expect it to error and require get_voltage_limits(bus, {SU/CU/NU} instead.
I opened an issue in PSY for the question of "do voltage fields like these get the units conversion treatment" here.
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Problem
With
warm_start = false, several POM builders still set start values:PhaseShifterAngle,TapRatioVariable,CosineApproximation)RegulatedVoltageMagnitudeThe solver then gets a partial MIP start.
Changes
Depends on Sienna-Platform/InfrastructureOptimizationModels.jl#172, which adds
set_start_value!and theskip_variablehook.add_variables!with per-bus bound and start-value hooks, replacing POM's own loop.skip_variablefor must-run units, replacing POM's custom builder.set_start_value!.[sources]points IOM atmb/warm-start-buguntil the IOM PR merges.Worth checking in review:
Tests
test/test_warm_start.jlbuilds unit commitment, DCP phase control, ACP, ACR with a regulated-voltage device, and LPAC models.With warm start off, no variable has a start value; with it on, the affected variables all do.
It also checks that must-run units carry no commitment variables.
The full suite passes (131,912 tests).
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