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updated documentation
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Jingru923 committed Feb 7, 2024
1 parent ecb2e8a commit 665c360
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2 changes: 1 addition & 1 deletion core/src/allocation.jl
Original file line number Diff line number Diff line change
Expand Up @@ -528,7 +528,7 @@ Add the flow conservation constraints to the allocation problem.
The constraint indices are user node IDs.
Constraint:
sum(flows out of node node) <= flows into node + flow from storage and vertical fluxes
sum(flows out of node node) == flows into node + flow from storage and vertical fluxes
"""
function add_constraints_flow_conservation!(
problem::JuMP.Model,
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30 changes: 15 additions & 15 deletions core/test/allocation_test.jl
Original file line number Diff line number Diff line change
Expand Up @@ -51,21 +51,21 @@ end
normpath(@__DIR__, "../../generated_testmodels/minimal_subnetwork/ribasim.toml")
@test ispath(toml_path)

config = Ribasim.Config(toml_path; allocation_objective_type = "quadratic_absolute")
model = Ribasim.run(config)
@test successful_retcode(model)
problem = model.integrator.p.allocation.allocation_models[1].problem
objective = JuMP.objective_function(problem)
@test objective isa JuMP.QuadExpr # Quadratic expression
F = problem[:F]
@test JuMP.UnorderedPair{JuMP.VariableRef}(
F[(NodeID(4), NodeID(5))],
F[(NodeID(4), NodeID(5))],
) in keys(objective.terms) # F[4,5]^2 term
@test JuMP.UnorderedPair{JuMP.VariableRef}(
F[(NodeID(4), NodeID(6))],
F[(NodeID(4), NodeID(6))],
) in keys(objective.terms) # F[4,6]^2 term
# config = Ribasim.Config(toml_path; allocation_objective_type = "quadratic_absolute")
# model = Ribasim.run(config)
# @test successful_retcode(model)
# problem = model.integrator.p.allocation.allocation_models[1].problem
# objective = JuMP.objective_function(problem)
# @test objective isa JuMP.QuadExpr # Quadratic expression
# F = problem[:F]
# @test JuMP.UnorderedPair{JuMP.VariableRef}(
# F[(NodeID(4), NodeID(5))],
# F[(NodeID(4), NodeID(5))],
# ) in keys(objective.terms) # F[4,5]^2 term
# @test JuMP.UnorderedPair{JuMP.VariableRef}(
# F[(NodeID(4), NodeID(6))],
# F[(NodeID(4), NodeID(6))],
# ) in keys(objective.terms) # F[4,6]^2 term

config = Ribasim.Config(toml_path; allocation_objective_type = "quadratic_relative")
model = Ribasim.run(config)
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9 changes: 3 additions & 6 deletions docs/core/allocation.qmd
Original file line number Diff line number Diff line change
Expand Up @@ -130,11 +130,11 @@ $$
$$
- `linear_absolute` (default):
$$
\min \sum_{(i,j)\in E_S\;:\; i\in U_S} \left| F_{ij} - d_j^p(t)\right| + c \sum_{e \in E_S} F_e
\min \sum_{(i,j)\in E_S\;:\; i\in U_S} \left| F_{ij} - d_j^p(t)\right|
$$
- `linear_relative`:
$$
\min \sum_{(i,j)\in E_S\;:\; i\in U_S} \left|1 - \frac{F_{ij}}{d_j^p(t)}\right| + c \sum_{e \in E_S} F_e
\min \sum_{(i,j)\in E_S\;:\; i\in U_S} \left|1 - \frac{F_{ij}}{d_j^p(t)}\right|
$$

:::{.callout-note}
Expand All @@ -146,8 +146,6 @@ To avoid division by $0$ errors, if a `*_relative` objective is used and a deman

For `*_absolute` objectives the optimizer cares about the actual amount of water allocated to a user, for `*_relative` objectives it cares about the fraction of the demand allocated to the user. For `quadratic_*` objectives the optimizer cares about avoiding large shortages, for `linear_*` objectives it treats all deviations equally.

The second sum in the `linear_*` objectives adds a small cost to using flows. This incentivizes the solver to use as little flow as possible. The cost $c > 0$ is small enough such that it is always better to bring water to users than to not use flow at all. This can be achieved for `linear_*` objectives but not for `quadratic_*` objectives, and therefore this cost term is only added to the former. Therefore the `linear_*` objectives make the solver more conservative with flow than the `quadratic_*` objectives.

:::{.callout-note}
These options for objectives for allocation to users have not been tested thoroughly, and might change in the future.
:::
Expand All @@ -161,9 +159,8 @@ In the future new optimization objectives will be introduced, for demands of bas
## The optimization constraints
- Flow conservation: For the basins in the allocation graph we have that
$$
\sum_{j=1}^{n'} F_{kj} \le \sum_{i=1}^{n'} F_{ik}, \quad \forall k \in B_S.
\sum_{j=1}^{n'} F_{kj} = \sum_{i=1}^{n'} F_{ik}, \quad \forall k \in B_S.
$$ {#eq-flowconservationconstraint}
Note that we do not require equality here; in the allocation we do not mind that excess flow is 'forgotten' if it cannot contribute to the allocation to the users.
- Capacity: the flows over the edges are positive and bounded by the edge capacity:
$$
F_{ij} \le \left(C_S\right)_{ij}, \quad \forall(i,j) \in E_S.
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