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fixpoint lib solver search strategy.ex
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lib/solver/search/strategy.ex

defmodule CPSolver.Search.Strategy do
alias CPSolver.Variable.Interface
alias CPSolver.Search.VariableSelector.{FirstFail, MostConstrained}
alias CPSolver.DefaultDomain, as: Domain
alias CPSolver.Search.ValueSelector.{Min, Max, Random}
require Logger
def default_strategy() do
{
:first_fail,
:indomain_min
}
end
def shortcut(:first_fail) do
&FirstFail.select_variable/1
end
def shortcut(:input_order) do
fn variables ->
Enum.sort_by(variables, fn %{index: idx} -> idx end)
|> List.first()
end
end
def shortcut(:most_constrained) do
&MostConstrained.select_variable/2
end
def shortcut(:indomain_min) do
Min
end
def shortcut(:indomain_max) do
Max
end
def shortcut(:indomain_random) do
Random
end
def most_constrained(break_even_fun \\ first_fail())
def most_constrained(break_even_fun) when is_function(break_even_fun) do
fn vars, data -> MostConstrained.select_variable(vars, data, break_even_fun) end
end
def most_constrained(shortcut) when is_atom(shortcut) do
most_constrained(shortcut(shortcut))
end
def first_fail(break_even_fun \\ &List.first/1)
def first_fail(break_even_fun) when is_function(break_even_fun, 1) do
first_fail(fn vars, _data -> break_even_fun.(vars) end)
end
def first_fail(break_even_fun) when is_function(break_even_fun, 2) do
fn vars, data ->
vars
|> FirstFail.get_minimals()
|> break_even_fun.(data)
end
end
def first_fail(shortcut) when is_atom(shortcut) do
first_fail(shortcut(shortcut))
end
def select_variable(variables, variable_choice) when is_atom(variable_choice) do
select_variable(variables, shortcut(variable_choice))
end
def select_variable(variables, variable_choice) when is_function(variable_choice) do
variables
|> Enum.reject(fn v -> Interface.fixed?(v) end)
|> then(fn
[] -> throw(all_vars_fixed_exception())
unfixed_vars -> variable_choice.(unfixed_vars)
end)
end
defp partition_impl(variable, value_choice) when is_atom(value_choice) do
shortcut(value_choice).select_value(variable)
end
defp partition_impl(variable, value_choice) when is_function(value_choice) do
value_choice.(variable)
end
def branch(variables, {variable_choice, partition_strategy}) do
branch(variables, variable_choice, partition_strategy, %{})
end
def branch(variables, {variable_choice, partition_strategy}, data) do
branch(variables, variable_choice, partition_strategy, data)
end
def branch(variables, variable_choice, partition_strategy, data \\ %{})
def branch(variables, variable_choice, partition_strategy, data) when is_atom(variable_choice) do
branch(variables, shortcut(variable_choice), partition_strategy, data)
end
def branch(variables, variable_choice, partition_strategy, data) when is_function(variable_choice, 2) do
variable_choice_arity1 = fn variables -> variable_choice.(variables, data) end
branch(variables, variable_choice_arity1, partition_strategy, data)
end
def branch(variables, variable_choice, partition_strategy, _data) when is_function(variable_choice, 1)
do
case select_variable(variables, variable_choice) do
nil ->
[]
selected_variable ->
{:ok, domain_partitions} =
partition(selected_variable, partition_strategy)
variable_partitions(selected_variable, domain_partitions, variables)
end
end
def partition(variable, value_choice) do
variable
|> partition_impl(value_choice)
|> split_domain_by(variable)
end
def all_vars_fixed_exception() do
:all_vars_fixed
end
def failed_variables_in_search_exception() do
:failed_variables_in_search
end
defp set_domain(variable, domain) do
Map.put(variable, :domain, domain)
end
defp variable_partitions(selected_variable, domain_partitions, variables) do
Enum.map(domain_partitions, fn {domain, constraint} ->
{Enum.map(variables, fn var ->
domain_copy =
((var.id == selected_variable.id && domain) || var.domain)
# var.domain
|> Domain.copy()
set_domain(var, domain_copy)
end), constraint}
end)
end
defp split_domain_by(value, variable) do
domain = Interface.domain(variable)
try do
{remove_changes, _domain} = Domain.remove(domain, value)
{:ok,
[
{
Domain.new(value),
%{variable.id => :fixed}
# Equal.new(variable, value)
},
{
domain,
%{variable.id => remove_changes}
# NotEqual.new(variable, value)
}
]}
rescue
:fail ->
Logger.error(
"Failure on partitioning with value #{inspect(value)}, domain: #{inspect(CPSolver.BitVectorDomain.raw(domain))}"
)
throw(:fail)
end
end
end