In order to solve the investment problem defined by an Antares study and its associated candidates.ini file, Antares Xpansion uses the Benders decomposition algorithm. The simulation options and algorithmic parameters are defined in the settings.ini file, located in the folder user/expansion/ of the Antares study.

!!! info

For more info about the signification of the parameters, visit the 
user documentation page for 
[Xpansion settings](https://antares-doc.readthedocs.io/en/latest/reference/xpansion-settings/).

The following section lists the configurable parameters. If the user does not specify the value of a parameter, its default value is used.

Name	Default value	Description
`optimality_gap`	`1`	Tolerance on absolute gap
`relative_gap`	`1e-6`	Tolerance on relative gap
`max_iteration`	`+Inf`	Maximum number of Benders iterations
`timelimit`	`1e12`	Timelimit (in seconds) of the Benders step
`uc_type`	`expansion_fast`	Unit-commitment type used by Antares
`master`	`integer`	Resolution mode of the master problem
`yearly-weights`	`None`	Path of the Monte-Carlo weights file
`solver`	`Cbc`	Name of the solver
`log_level`	`0`	Logs severity
`additional-constraints`	`None`	Path of the additional constraints file
`separation_parameter`	`0.5`	Step size for the in-out separation
`relaxed_optimality_gap`	`1e-5`	Threshold to switch from relaxed to integer master
`batch_size`	`0`	Number of subproblems per batch
`master_solution_tolerance`	`1e-4`	Tolerance for rounding master solution variables
`cut_coefficient_tolerance`	`5e-3`	Tolerance for rounding cut coefficients and rhs

The format is a standard .ini and should follow this template:

 title="Example `settings.ini`"
uc_type = expansion_fast
master = integer
optimality_gap = 0
max_iteration = 100
timelimit = 300
additional-constraints = constraint.txt
log_level = 0