def _parse_declaration(solver: pywraplp.Solver, core_line: str, line_nr: int,
var_names: set):
spl_whitespace = core_line.split(maxsplit=1)
if spl_whitespace[0] != "int":
raise ValueError("Declaration on line %d should start with \"int \"." %
line_nr)
if len(spl_whitespace) != 2:
raise ValueError("Declaration on line %d has no variables." % line_nr)
spl_variables = spl_whitespace[1].split(",")
for raw_var in spl_variables:
clean_var = raw_var.strip()
if not re.match(_REGEXP_SINGLE_VAR_NAME_ALL, clean_var):
raise ValueError(
"Non-permitted variable name (\"%s\") on line %d." %
(clean_var, line_nr))
if clean_var in var_names:
raise ValueError("Variable \"%s\" declared again on line %d." %
(clean_var, line_nr))
var_names.add(clean_var)
solver.IntVar(-solver.infinity(), solver.infinity(), clean_var)
def _add_stock_variables(num_types: int, num_time_periods: int, solver: Solver) \
-> Dict[V, Variable]:
"""Create stock variables.
A stock variable $s^t_p$ is a non-negative real variable which represents the number of
items of type $t$ on stock in time period $p$.
:param num_types: the number of considered types
:param num_time_periods: the number of considered time periods
:param solver: the underlying solver for which to built the variables
:return: A dictionary mapping each stock variable to its solver variable
"""
stock_vars = dict()
for (item_type, time_period) in product(range(num_types),
range(-1, num_time_periods)):
stock_vars[V(type=item_type, period=time_period)] = \
solver.NumVar(lb=0., ub=solver.infinity(), name=f's_{item_type}_{time_period}')
module_logger.info(f'Created {len(stock_vars)} stock variables.')
return stock_vars
def _set_coefficients(solver: pywraplp.Solver, objective_or_constraint,
coefficient_part: str, line_nr: int, var_names: set):
# Strip the coefficient whitespace
remainder = coefficient_part.strip()
if len(remainder) == 0:
raise ValueError("No variables present in equation on line %d." %
line_nr)
# All variables found
var_names_found = set()
running_constant_sum = 0.0
had_at_least_one_variable = False
while len(remainder) != 0:
# Combination sign
coefficient = 1.0
combination_sign_match = re.search(r"^[-+]", remainder)
if combination_sign_match is not None:
if combination_sign_match.group() == "-":
coefficient = -1.0
remainder = remainder[1:].strip()
# Real sign
sign_match = re.search(r"^[-+]", remainder)
if sign_match is not None:
if sign_match.group() == "-":
coefficient = coefficient * -1.0
remainder = remainder[
1:] # There is no strip() here, as it must be directly in front of the mantissa
# Mantissa and exponent
mantissa_exp_match = re.search(r"^(\d+(\.\d*)?|\.\d+)([eE][-+]?\d+)?",
remainder)
whitespace_after = False
if mantissa_exp_match is not None:
coefficient = coefficient * float(mantissa_exp_match.group())
remainder = remainder[mantissa_exp_match.span()[1]:]
stripped_remainder = remainder.strip()
if len(remainder) != len(stripped_remainder):
whitespace_after = True
remainder = stripped_remainder
# Variable name
var_name_match = re.search(_REGEXP_SINGLE_VAR_NAME_START, remainder)
if var_name_match is not None:
# It must have had at least one variable
had_at_least_one_variable = True
# Retrieve clean variable name
clean_var = var_name_match.group()
var_names.add(clean_var)
if clean_var in var_names_found:
raise ValueError(
"Variable \"%s\" found more than once on line %d." %
(clean_var, line_nr))
var_names_found.add(clean_var)
solver_var = solver.LookupVariable(clean_var)
if solver_var is None:
solver_var = solver.NumVar(-solver.infinity(),
solver.infinity(), clean_var)
# Set coefficient
objective_or_constraint.SetCoefficient(solver_var, coefficient)
# Strip what we matched
remainder = remainder[var_name_match.span()[1]:]
stripped_remainder = remainder.strip()
whitespace_after = False
if len(remainder) != len(stripped_remainder):
whitespace_after = True
remainder = stripped_remainder
elif mantissa_exp_match is None:
raise ValueError(
"Cannot process remainder coefficients of \"%s\" on line %d." %
(remainder, line_nr))
else:
running_constant_sum += coefficient
# At the end of each element there either:
# (a) Must be whitespace (e.g., x1 x2 <= 10)
# (b) The next combination sign (e.g., x1+x2 <= 10)
# (c) Or it was the last one, as such remainder is empty (e.g., x1 <= 10)
if len(remainder) != 0 and not whitespace_after and remainder[
0:1] != "-" and remainder[0:1] != "+":
raise ValueError(
"Unexpected next character \"%s\" on line %d (expected whitespace or "
"combination sign character)." % (remainder[0:1], line_nr))
# There must have been at least one variable
if not had_at_least_one_variable:
raise ValueError(
"Not a single variable present in the coefficients on line %d." %
line_nr)
return running_constant_sum
def _parse_constraint(solver: pywraplp.Solver, core_line: str, line_nr: int,
var_names: set):
# We don't care about the coefficient name before the colon
constraint_part = core_line
spl_colon = core_line.split(":", maxsplit=1)
if len(spl_colon) > 1:
constraint_part = spl_colon[1].strip()
# Equality constraint
if constraint_part.find("=") >= 0 and constraint_part.find(
"<=") == -1 and constraint_part.find(">=") == -1:
equality_spl = constraint_part.split("=")
if len(equality_spl) > 2:
raise ValueError(
"Equality constraint on line %d has multiple equal signs." %
line_nr)
if not _is_valid_constant_float(equality_spl[1]):
raise ValueError(
"Right hand side (\"%s\") of equality constraint on line %d is not a float "
"(e.g., variables are not allowed there!)." %
(equality_spl[1], line_nr))
equal_value = float(equality_spl[1])
constraint = solver.Constraint(equal_value, equal_value)
constant = _set_coefficients(solver, constraint, equality_spl[0],
line_nr, var_names)
constraint.SetLb(constraint.Lb() - constant)
constraint.SetUb(constraint.Ub() - constant)
_attempt_to_improve_var_bounds_two_hs(solver, equality_spl[0], True,
equality_spl[1], equality_spl[1])
# Inequality constraints
else:
# Replace all of these inequality signs, because they are equivalent
constraint_part = constraint_part.replace("<=", "<").replace(">=", ">")
# lower bound < ... < upper bound
if constraint_part.count("<") == 2:
spl = constraint_part.split("<")
if not _is_valid_constant_float(spl[0]):
raise ValueError(
"Left hand side (\"%s\") of inequality constraint on line %d is not a float "
"(e.g., variables are not allowed there!)." %
(spl[0], line_nr))
if not _is_valid_constant_float(spl[2]):
raise ValueError(
"Right hand side (\"%s\") of inequality constraint on line %d is not a float "
"(e.g., variables are not allowed there!)." %
(spl[2], line_nr))
constraint = solver.Constraint(float(spl[0]), float(spl[2]))
constant = _set_coefficients(solver, constraint, spl[1], line_nr,
var_names)
constraint.SetLb(constraint.Lb() - constant)
constraint.SetUb(constraint.Ub() - constant)
_attempt_to_improve_var_bounds_two_hs(solver, spl[1], True, spl[0],
spl[2])
# upper bound > ... > lower bound
elif constraint_part.count(">") == 2:
spl = constraint_part.split(">")
if not _is_valid_constant_float(spl[0]):
raise ValueError(
"Left hand side (\"%s\") of inequality constraint on line %d is not a float "
"(e.g., variables are not allowed there!)." %
(spl[0], line_nr))
if not _is_valid_constant_float(spl[2]):
raise ValueError(
"Right hand side (\"%s\") of inequality constraint on line %d is not a float "
"(e.g., variables are not allowed there!)." %
(spl[2], line_nr))
constraint = solver.Constraint(float(spl[2]), float(spl[0]))
constant = _set_coefficients(solver, constraint, spl[1], line_nr,
var_names)
constraint.SetLb(constraint.Lb() - constant)
constraint.SetUb(constraint.Ub() - constant)
_attempt_to_improve_var_bounds_two_hs(solver, spl[1], False,
spl[0], spl[2])
# ... < upper bound
elif constraint_part.count("<") == 1:
spl = constraint_part.split("<")
if not _is_valid_constant_float(spl[1]):
raise ValueError(
"Right hand side (\"%s\") of inequality constraint on line %d is not a float "
"(e.g., variables are not allowed there!)." %
(spl[1], line_nr))
constraint = solver.Constraint(-solver.infinity(), float(spl[1]))
constant = _set_coefficients(solver, constraint, spl[0], line_nr,
var_names)
constraint.SetUb(constraint.Ub() - constant)
_attempt_to_improve_var_bounds_one_hs(solver, spl[0], True, spl[1])
# ... > lower bound
elif constraint_part.count(">") == 1:
spl = constraint_part.split(">")
if not _is_valid_constant_float(spl[1]):
raise ValueError(
"Right hand side (\"%s\") of inequality constraint on line %d is not a float "
"(e.g., variables are not allowed there!)." %
(spl[1], line_nr))
constraint = solver.Constraint(float(spl[1]), solver.infinity())
constant = _set_coefficients(solver, constraint, spl[0], line_nr,
var_names)
constraint.SetLb(constraint.Lb() - constant)
_attempt_to_improve_var_bounds_one_hs(solver, spl[0], False,
spl[1])
# ...
elif constraint_part.count(">") == 0 and constraint_part.count(
"<") == 0:
raise ValueError(
"No (in)equality sign present for constraint on line %d." %
line_nr)
# Some strange combination
else:
raise ValueError(
"Too many (in)equality signs present for constraint on line %d."
% line_nr)
