"""
A real-world multi-objective problem suite (the RE benchmark set)
Tanabe, R. & Ishibuchi, H. (2020). An easy-to-use real-world multi-objective
optimization problem suite. Applied soft computing, 89, 106078.
https://doi.org/10.1016/j.asoc.2020.106078
https://github.com/ryojitanabe/reproblems/blob/master/reproblem_python_ver/reproblem.py
"""
from desdeo_problem.problem.Variable import Variable
from desdeo_problem.problem.Objective import ScalarObjective
from desdeo_problem.problem.Problem import MOProblem, ProblemBase
from desdeo_problem import ScalarConstraint, problem
import numpy as np
[docs]def re21(var_iv: np.array = np.array([2, 2, 2, 2])) -> MOProblem:
""" Four bar truss design problem.
Two objectives and four variables.
Arguments:
var_iv (np.array): Optional, initial variable values.
Defaults are [2, 2, 2, 2]. x1, x4 ∈ [a, 3a], x2, x3 ∈ [√2 a, 3a]
and a = F / sigma
Returns:
MOProblem: a problem object.
"""
# Parameters
F = 10.0
sigma = 10.0
E = 2.0 * 1e5
L = 200.0
a = F / sigma
# Check the number of variables
if (np.shape(np.atleast_2d(var_iv)[0]) != (4,)):
raise RuntimeError("Number of variables must be four")
# Lower bounds
lb = np.array([a, np.sqrt(2) * a, np.sqrt(2) * a, a])
# Upper bounds
ub = np.array([3 * a, 3 * a, 3 * a, 3 * a])
# Check the variable bounds
if np.any(lb > var_iv) or np.any(ub < var_iv):
raise ValueError("Initial variable values need to be between lower and upper bounds")
def f_1(x: np.ndarray) -> np.ndarray:
x = np.atleast_2d(x)
return L * ((2 * x[:, 0]) + np.sqrt(2.0) * x[:, 1] + np.sqrt(x[:, 2]) + x[:, 3])
def f_2(x: np.ndarray) -> np.ndarray:
x = np.atleast_2d(x)
return ((F * L) / E) * ((2.0 / x[:, 0]) +
(2.0 * np.sqrt(2.0) / x[:, 1]) - (2.0 * np.sqrt(2.0) / x[:, 2]) + (2.0 / x[:, 3]))
objective_1 = ScalarObjective(name="minimize the structural volume", evaluator=f_1, maximize=[False])
objective_2 = ScalarObjective(name="minimize the joint displacement", evaluator=f_2, maximize=[False])
objectives = [objective_1, objective_2]
# The four variables determine the length of four bars
x_1 = Variable("x_1", 2 * a, a, 3 * a)
x_2 = Variable("x_2", 2 * a, (np.sqrt(2.0) * a), 3 * a)
x_3 = Variable("x_3", 2 * a, (np.sqrt(2.0) * a), 3 * a)
x_4 = Variable("x_4", 2 * a, a, 3 * a)
variables = [x_1, x_2, x_3, x_4]
problem = MOProblem(variables=variables, objectives=objectives)
return problem
[docs]def re22(var_iv: np.array = np.array([7.2, 10, 20])) -> MOProblem:
""" Reinforced concrete beam design problem.
2 objectives, 3 variables and 2 constraints.
Arguments:
var_iv (np.array): Optional, initial variable values.
Defaults are [7.2, 10, 20]. x2 ∈ [0, 20] and x3 ∈ [0, 40].
x1 has a pre-defined discrete value from 0.2 to 15.
Returns:
MOProblem: a problem object.
"""
# Check the number of variables
if (np.shape(np.atleast_2d(var_iv)[0]) != (3,)):
raise RuntimeError("Number of variables must be three")
# Lower bounds
lb = np.array([0.2, 0, 0])
# Upper bounds
ub = np.array([15, 20, 40])
# Check the variable bounds
if np.any(lb > var_iv) or np.any(ub < var_iv):
raise ValueError("Initial variable values need to be between lower and upper bounds")
# x1 pre-defined discrete values
feasible_vals = np.array([0.20, 0.31, 0.40, 0.44, 0.60, 0.62, 0.79, 0.80, 0.88, 0.93,
1.0, 1.20, 1.24, 1.32, 1.40, 1.55, 1.58, 1.60, 1.76, 1.80,
1.86, 2.0, 2.17, 2.20, 2.37, 2.40, 2.48, 2.60, 2.64, 2.79,
2.80, 3.0, 3.08, 3.10, 3.16, 3.41, 3.52, 3.60, 3.72, 3.95,
3.96, 4.0, 4.03, 4.20, 4.34, 4.40, 4.65, 4.74, 4.80, 4.84,
5.0, 5.28, 5.40, 5.53, 5.72, 6.0, 6.16, 6.32, 6.60, 7.11,
7.20, 7.80, 7.90, 8.0, 8.40, 8.69, 9.0, 9.48, 10.27, 11.0,
11.06, 11.85, 12.0, 13.0, 14.0, 15.0])
# Returns discrete value for x1
def feas_val(x: np.ndarray) -> np.array:
fv_2d = np.repeat(np.atleast_2d(feasible_vals), x.shape[0], axis=0)
idx = np.abs(fv_2d.T - x[:, 0]).argmin(axis=0)
x[:, 0] = feasible_vals[idx]
return x
# Constrain functions
def g_1(x: np.ndarray, _ = None) -> np.ndarray:
x = np.atleast_2d(x)
x = feas_val(x)
return x[:, 0] * x[:, 2] - 7.735 * (x[:, 0]**2 / x[:, 1]) - 180
def g_2(x: np.ndarray, _ = None) -> np.ndarray:
x = np.atleast_2d(x)
return 4 - x[:, 2] / x[:, 1]
# Objective functions
def f_1(x: np.ndarray) -> np.ndarray:
x = np.atleast_2d(x)
x = feas_val(x)
return (29.4 * x[:, 0]) + (0.6 * x[:, 1] * x[:,2])
def f_2(x: np.ndarray) -> np.ndarray:
x = np.atleast_2d(x)
sum1 = g_1(x)
sum2 = g_2(x)
sum1 = np.where(sum1 > 0, sum1, 0)
sum2 = np.where(sum2 > 0, sum2, 0)
return sum1 + sum2
objective_1 = ScalarObjective(name="minimize the total cost of concrete and reinforcing steel of the beam",
evaluator=f_1, maximize=[False])
objective_2 = ScalarObjective(name="the sum of the four constraint violations", evaluator=f_2, maximize=[False])
objectives = [objective_1, objective_2]
cons_1 = ScalarConstraint("c_1", 3, 2, g_1)
cons_2 = ScalarConstraint("c_2", 3, 2, g_2)
constraints = [cons_1, cons_2]
x_1 = Variable("the area of the reinforcement", 7.2, 0.2, 15)
x_2 = Variable("the width of the beam", 10, 0, 20)
x_3 = Variable("the depth of the beam", 20, 0, 40)
variables = [x_1, x_2, x_3]
problem = MOProblem(variables=variables, objectives=objectives, constraints=constraints)
return problem
[docs]def re23(var_iv: np.array = np.array([50, 50, 100, 120])) -> MOProblem:
""" Pressure vesssel design problem.
2 objectives, 4 variables and 3 constraints.
Arguments:
var_iv (np.array): Optional, initial variable values.
Defaults are [50, 50, 100, 120]. x1 and x2 ∈ {1, ..., 100},
x3 ∈ [10, 200] and x4 ∈ [10, 240].
x1 and x2 are integer multiples of 0.0625.
Returns:
MOProblem: a problem object.
"""
# Check the number of variables
if (np.shape(np.atleast_2d(var_iv)[0]) != (4,)):
raise RuntimeError("Number of variables must be four")
# Lower bounds
lb = np.array([1, 1, 10, 10])
ub = np.array([100, 100, 200, 240])
# Check the variable bounds
if np.any(lb > var_iv) or np.any(ub < var_iv):
raise ValueError("Initial variable values need to be between lower and upper bounds")
# Constrain functions
def g_1(x: np.ndarray, _ = None) -> np.ndarray:
x = np.atleast_2d(x)
x = x.astype(float)
x[:, 0] = 0.0625 * (np.round(x[:,0]))
return x[:, 0] - (0.0193 * x[:, 2])
def g_2(x: np.ndarray, _ = None) -> np.ndarray:
x = np.atleast_2d(x)
x = x.astype(float)
x[:, 1] = 0.0625 * (np.round(x[:,1]))
return x[:, 1] - (0.00954 * x[:, 2])
def g_3(x: np.ndarray, _ = None) -> np.ndarray:
x = np.atleast_2d(x)
return (np.pi * x[:, 2]**2 * x[:, 3]) + ((4/3) * np.pi * x[:, 2]**3) - 1296000
# Objective functions
def f_1(x: np.ndarray) -> np.ndarray:
x = np.atleast_2d(x)
x = x.astype(float)
x[:, 0] = 0.0625 * (np.round(x[:,0]))
x[:, 1] = 0.0625 * (np.round(x[:,1]))
return (
(0.6224 * x[:, 0] * x[:, 2] * x[:, 3]) + (1.7781 * x[:, 1] * x[:, 2]**2) +
(3.1661 * x[:, 0]**2 * x[:, 3]) + (19.84 * x[:, 0]**2 * x[:, 2])
)
def f_2(x: np.ndarray) -> np.ndarray:
x = np.atleast_2d(x)
sum1 = g_1(x)
sum2 = g_2(x)
sum3 = g_3(x)
sum1 = np.where(sum1 > 0, sum1, 0)
sum2 = np.where(sum2 > 0, sum2, 0)
sum3 = np.where(sum3 > 0, sum3, 0)
return sum1 + sum2 + sum3
objective_1 = ScalarObjective(name="minimize to total cost of a clyndrical pressure vessel", evaluator=f_1, maximize=[False])
objective_2 = ScalarObjective(name="the sum of the four constraint violations", evaluator=f_2, maximize=[False])
objectives = [objective_1, objective_2]
cons_1 = ScalarConstraint("c_1", 4, 2, g_1)
cons_2 = ScalarConstraint("c_2", 4, 2, g_2)
cons_3 = ScalarConstraint("c_3", 4, 2, g_3)
constraints = [cons_1, cons_2, cons_3]
x_1 = Variable("the thicknesses of the shell", 50, 1, 100)
x_2 = Variable("the the head of pressure vessel", 50, 1, 100)
x_3 = Variable("the inner radius", 100, 10, 200)
x_4 = Variable("the length of the cylindrical section", 120, 10, 240)
variables = [x_1, x_2, x_3, x_4]
problem = MOProblem(variables=variables, objectives=objectives, constraints=constraints)
return problem
[docs]def re24(var_iv : np.array = np.array([2, 25])) -> MOProblem:
""" Hatch cover design problem.
2 objectives, 2 variables and 4 constraints.
Arguments:
var_iv (np.array): Optional, initial variable values.
Defaults are [2, 25]. x1 ∈ [0.5, 4] and
x2 ∈ [4, 50].
Returns:
MOProblem: a problem object.
"""
# Check the number of variables
if (np.shape(np.atleast_2d(var_iv)[0]) != (2,)):
raise RuntimeError("Number of variables must be two")
# Lower bounds
lb = np.array([0.5, 4])
# Upper bounds
ub = np.array([4, 50])
# Check the variable bounds
if np.any(lb > var_iv) or np.any(ub < var_iv):
raise ValueError("Initial variable values need to be between lower and upper bounds")
# Constrain functions
def g_1(x: np.ndarray, _ = None) -> np.ndarray:
x = np.atleast_2d(x)
return 1.0 - ((4500 / (x[:, 0] * x[:, 1])) / 700)
def g_2(x: np.ndarray, _ = None) -> np.ndarray:
x = np.atleast_2d(x)
return 1.0 - ((1800 / x[:, 1]) / 450)
def g_3(x: np.ndarray, _ = None) -> np.ndarray:
x = np.atleast_2d(x)
return 1.0 - (((56.2 * 10000) / (700000 * x[:, 0] * x[:, 1]**2)) / 1.5)
def g_4(x: np.ndarray, _ = None) -> np.ndarray:
x = np.atleast_2d(x)
return 1.0 - ((4500 / (x[:,0] * x[:, 1])) / ((700000 * x[:, 0]**2) / 100))
# Objective functions
def f_1(x: np.ndarray) -> np.ndarray:
x = np.atleast_2d(x)
return x[:, 0] + 120 * x[:, 1]
def f_2(x: np.ndarray) -> np.ndarray:
x = np.atleast_2d(x)
sum1 = g_1(x)
sum2 = g_2(x)
sum3 = g_3(x)
sum4 = g_4(x)
sum1 = np.where(sum1 > 0, sum1, 0)
sum2 = np.where(sum2 > 0, sum2, 0)
sum3 = np.where(sum3 > 0, sum3, 0)
sum4 = np.where(sum4 > 0, sum4, 0)
return sum1 + sum2 + sum3 + sum4
objective_1 = ScalarObjective(name="to minimize the weight of the hatch cover", evaluator=f_1, maximize=[False])
objective_2 = ScalarObjective(name="the sum of the four constraint violations", evaluator=f_2, maximize=[False])
objectives = [objective_1, objective_2]
cons_1 = ScalarConstraint("c_1", 2, 2, g_1)
cons_2 = ScalarConstraint("c_2", 2, 2, g_2)
cons_3 = ScalarConstraint("c_3", 2, 2, g_3)
cons_4 = ScalarConstraint("c_4", 2, 2, g_4)
constraints = [cons_1, cons_2, cons_3, cons_4]
x_1 = Variable("the flange thickness", 2, 0.5, 4)
x_2 = Variable("the beam height", 25, 4, 50)
variables = [x_1, x_2]
problem = MOProblem(variables=variables, objectives=objectives, constraints=constraints)
return problem
[docs]def re25(var_iv: np.array = np.array([35, 15, 0.207])) -> MOProblem:
""" Coil compression spring design problem.
2 objectives, 3 variables and 6 constraints.
Arguments:
var_iv (np.array): Optional, initial variable values.
Defaults are [35, 15, 0.207]. x1 ∈ {1, ..., 70} and x2 ∈ [0.6, 30].
x3 has a pre-defined discrete value from 0.009 to 0.5.
Returns:
MOProblem: a problem object.
"""
# Check the number of variables
if (np.shape(np.atleast_2d(var_iv)[0]) != (3,)):
raise RuntimeError("Number of variables must be three")
# Lower bounds
lb = np.array([1, 0.6, 0.009])
# Upper bounds
ub = np.array([70, 30, 0.5])
# Check the variable bounds
if np.any(lb > var_iv) or np.any(ub < var_iv):
raise ValueError("Initial variable values need to be between lower and upper bounds")
# x3 pre-defined discrete values
feasible_vals = np.array([0.009, 0.0095, 0.0104, 0.0118, 0.0128, 0.0132, 0.014, 0.015,
0.0162, 0.0173, 0.018, 0.02, 0.023, 0.025, 0.028, 0.032, 0.035,
0.041, 0.047, 0.054, 0.063, 0.072, 0.08, 0.092, 0.105, 0.12,
0.135, 0.148, 0.162, 0.177, 0.192, 0.207, 0.225, 0.244, 0.263,
0.283, 0.307, 0.331, 0.362, 0.394, 0.4375, 0.5])
# Returns discrete value for x3
def feas_val(x: np.ndarray) -> np.array:
fv_2d = np.repeat(np.atleast_2d(feasible_vals), x.shape[0], axis=0)
idx = np.abs(fv_2d.T - x[:, 2]).argmin(axis=0)
x[:, 2] = feasible_vals[idx]
return x
# Constrain functions
def g_1(x: np.ndarray, _ = None) -> np.ndarray:
x = np.atleast_2d(x)
x = feas_val(x)
return (
-((8 * (((4.0 * (x[:, 1] / x[:, 2]) - 1) /
(4.0 * (x[:, 1] / x[:, 2]) - 4)) +
((0.615 * x[:, 2]) / x[:, 1])) * 1000 * x[:, 1])
/ (np.pi * x[:, 2]**3 )) + 189000
)
def g_2(x: np.ndarray, _ = None) -> np.ndarray:
x = np.atleast_2d(x)
x = feas_val(x)
return (
- ( 1000 / ( ( 11.5 * 10**6 * x[:, 2]**4) / ( 8 * np.round(x[:, 0]) * x[:, 1]**3 ) ) ) + 1.05 * ( np.round( x[:, 0]) + 2) * x[:, 2] + 14
)
def g_3(x: np.ndarray, _ = None) -> np.ndarray:
x = np.atleast_2d(x)
x = feas_val(x)
return (
-3 + (x[:, 1] / x[:, 2])
)
def g_4(x: np.ndarray, _ = None) -> np.ndarray:
x = np.atleast_2d(x)
return (
- (300 / ((11.5 * 10**6 * x[:, 2]**4) / (8 * np.round(x[:, 0]) * x[:, 1]**3))) + 6
)
def g_5(x: np.ndarray, _ = None) -> np.ndarray:
x = np.atleast_2d(x)
x = feas_val(x)
return (
-(300 / ((11.5 * 10**6 * x[:, 2]**4) / (8 * np.round(x[:, 0]) * x[:, 1]**3))) - ((1000 - 300) / ((11.5 * 10**6 * x[:, 2]**4) / (8 * np.round(x[:, 0]) * x[:, 1]**3))) - (1.05 * (np.round(x[:, 0]) + 2) * x[:, 2]) + ((1000 / ((11.5 * 10**6 * x[:, 2]**4) / (8 * np.round(x[:, 0]) * x[:, 1]**3))) + (1.05 * ( np.round(x[:, 0]) + 2) * x[:, 2]))
)
def g_6(x: np.ndarray, _ = None) -> np.ndarray:
x = np.atleast_2d(x)
x = feas_val(x)
return (
-1.25 + ((1000 - 300) / ((11.5 * 10**6 * x[:, 2]**4) / (8 * np.round(x[:, 0]) * x[:, 1]**3)))
)
# Objective functions
def f_1(x: np.ndarray) -> np.ndarray:
x = np.atleast_2d(x)
x = feas_val(x)
return ((np.pi * np.pi * x[:,1] * x[:,2]**2 * ((np.round(x[:,0])) + 2)) / 4.0)
def f_2(x: np.ndarray) -> np.ndarray:
x = np.atleast_2d(x)
sum1 = g_1(x)
sum2 = g_2(x)
sum3 = g_3(x)
sum4 = g_4(x)
sum5 = g_5(x)
sum6 = g_6(x)
sum1 = np.where(sum1 > 0, sum1, 0)
sum2 = np.where(sum2 > 0, sum2, 0)
sum3 = np.where(sum3 > 0, sum3, 0)
sum4 = np.where(sum4 > 0, sum4, 0)
sum5 = np.where(sum5 > 0, sum5, 0)
sum6 = np.where(sum6 > 0, sum6, 0)
return sum1 + sum2 + sum3 + sum4 + sum5 + sum6
objective_1 = ScalarObjective(name="minimize the volume of spring steel wire which is used to manufacture the spring",
evaluator=f_1, maximize=[False])
objective_2 = ScalarObjective(name="the sum of the four constraint violations", evaluator=f_2, maximize=[False])
objectives = [objective_1, objective_2]
cons_1 = ScalarConstraint("c_1", 3, 2, g_1)
cons_2 = ScalarConstraint("c_2", 3, 2, g_2)
cons_3 = ScalarConstraint("c_3", 3, 2, g_3)
cons_4 = ScalarConstraint("c_4", 3, 2, g_4)
cons_5 = ScalarConstraint("c_5", 3, 2, g_5)
cons_6 = ScalarConstraint("c_6", 3, 2, g_6)
constraints = [cons_1, cons_2, cons_3, cons_4, cons_5, cons_6]
x_1 = Variable("the number of spring coils", 35, 1, 70)
x_2 = Variable("the outside diameter of the spring", 15, 0.6, 30)
x_3 = Variable("the spring wire diameter", 0.207, 0.009, 0.5)
variables = [x_1, x_2, x_3]
problem = MOProblem(variables=variables, objectives=objectives, constraints=constraints)
return problem
[docs]def re31(var_iv: np.array = np.array([50.0, 50.0, 2.0])) -> MOProblem:
""" Two bar truss design problem.
Arguments:
var_iv (np.array): Optional, initial variable values.
Defaults are [50.0, 50.0, 2.0]. x1 and x2 ∈ [0.00001, 100]
and x3 ∈ [1.0, 3.0].
Returns:
MOProblem: a problem object.
"""
# Check the number of variables
if (np.shape(np.atleast_2d(var_iv)[0]) != (3,)):
raise RuntimeError("Number of variables must be three")
# Lower bounds
lb = np.array([0.00001, 0.00001, 1.0])
# Upper bounds
ub = np.array([100.0, 100.0, 3.0])
# Check the variable bounds
if np.any(lb > var_iv) or np.any(ub < var_iv):
raise ValueError("Initial variable values need to be between lower and upper bounds")
# Objective functions
def f_1(x: np.ndarray) -> np.ndarray:
x = np.atleast_2d(x)
return (
x[:, 0] * np.sqrt(16 + x[:, 2]**2 )
+ x[:, 1] * np.sqrt(1 + x[:, 2]**2 )
)
def f_2(x: np.ndarray) -> np.ndarray:
x = np.atleast_2d(x)
return (
(20 * np.sqrt(16 + x[:, 2]**2 )
/ ( x[:, 2] * x[:, 0] ))
)
# Constrain functions
def g_1(x: np.ndarray, _ = None) -> np.ndarray:
x = np.atleast_2d(x)
return (
0.1 - f_1(x)
)
def g_2(x: np.ndarray, _ = None) -> np.ndarray:
x = np.atleast_2d(x)
return (
10**5 - f_2(x)
)
def g_3(x: np.ndarray, _ = None) -> np.ndarray:
x = np.atleast_2d(x)
return (
10**5
- ((80 * np.sqrt(1 + x[:, 2]**2 )
/ (x[:, 2] * x[:, 1])))
)
# Third objective
def f_3(x: np.ndarray) -> np.ndarray:
x = np.atleast_2d(x)
sum1 = g_1(x)
sum2 = g_2(x)
sum3 = g_3(x)
sum1 = np.where(sum1 > 0, sum1, 0)
sum2 = np.where(sum2 > 0, sum2, 0)
sum3 = np.where(sum3 > 0, sum3, 0)
return sum1 + sum2 + sum3
objective_1 = ScalarObjective(name="minimize the structural weight", evaluator=f_1, maximize=[False])
objective_2 = ScalarObjective(name="minimize the resultant displacement of join", evaluator=f_2, maximize=[False])
objective_3 = ScalarObjective(name="the sum of the four constraint violations", evaluator=f_3, maximize=[False])
objectives = [objective_1, objective_2, objective_3]
cons_1 = ScalarConstraint("c_1", 3, 3, g_1)
cons_2 = ScalarConstraint("c_2", 3, 3, g_2)
cons_3 = ScalarConstraint("c_3", 3, 3, g_3)
constraints = [cons_1, cons_2, cons_3]
x_1 = Variable("the length of the bar", 50.0, 0.00001, 100)
x_2 = Variable("the length of the bar", 50.0, 0.00001, 100)
x_3 = Variable("the spring wire diameter", 2.0, 1.0, 3.0)
variables = [x_1, x_2, x_3]
problem = MOProblem(variables=variables, objectives=objectives, constraints=constraints)
return problem
[docs]def re32(var_iv: np.array = np.array([2.5, 5.0, 5.0, 2.5])) -> MOProblem:
""" Welded beam design problem.
Arguments:
var_iv (np.array): Optional, initial variable values.
Defaults are [2.5, 5.0, 5.0, 2.5]. x1, x4 ∈ [0.125, 5]
and x2, x3 ∈ [0.1, 10.0].
Returns:
MOProblem: a problem object.
"""
# Check the number of variables
if (np.shape(np.atleast_2d(var_iv)[0]) != (4,)):
raise RuntimeError("Number of variables must be four")
# Lower bounds
lb = np.array([0.125, 0.1, 0.1, 0.125])
# Upper bounds
ub = np.array([5, 10, 10, 5])
# Check the variable bounds
if np.any(lb > var_iv) or np.any(ub < var_iv):
raise ValueError("Initial variable values need to be between lower and upper bounds")
def tau(x: np.ndarray) -> np.ndarray:
x = np.atleast_2d(x)
return (
np.sqrt(
(6000 / (np.sqrt(2) * x[:, 0] * x[:, 1]))**2 +
((2 * (6000 / (np.sqrt(2) * x[:, 0] * x[:, 1])) *
((6000 * (14 + (x[:, 1] / 2))) *
(np.sqrt( ( (x[:,1]**2) / 4.0) +
((x[:, 0] + x[:, 2]) / 2)**2 ))) /
(2 * (np.sqrt(2) * x[:, 0] * x[:, 1] *
((x[:,1]**2)/12 + ((x[:,0] + x[:,2]) / 2)**2) )) * x[:, 1]) /
(2 * (np.sqrt( ( (x[:,1]**2) / 4.0) + ((x[:, 0] + x[:, 2]) / 2)**2 )))) +
(((6000 * (14 + (x[:, 1] / 2))) *
(np.sqrt( ( (x[:,1]**2) / 4.0) +
((x[:, 0] + x[:, 2]) / 2)**2 ))) /
(2 * (np.sqrt(2) * x[:, 0] * x[:, 1] *
((x[:,1]**2)/12 + ((x[:,0] + x[:,2]) / 2)**2) )))**2
)
)
def sigma(x: np.ndarray) -> np.ndarray:
x = np.atleast_2d(x)
return (
(6 * 6000 * 14) / (x[:, 3] * x[:, 2]**2)
)
def p_c(x: np.ndarray) -> np.ndarray:
x = np.atleast_2d(x)
return (
((4.013 * 30 * 10**6 * np.sqrt((x[:, 2]**2 *
x[:, 3]**6) / 36)) / (14**2) ) *
(1 - (x[:, 2] / (2 * 14)) * np.sqrt((30 * 10**6) /
(4 * 12 * 10**6)))
)
# Constrain functions
def g_1(x: np.ndarray, _ = None) -> np.ndarray:
x = np.atleast_2d(x)
return (
13600 - tau(x)
)
def g_2(x: np.ndarray, _ = None) -> np.ndarray:
x = np.atleast_2d(x)
return (
30000 - sigma(x)
)
def g_3(x: np.ndarray, _ = None) -> np.ndarray:
x = np.atleast_2d(x)
return (
x[:, 3] - x[:, 0]
)
def g_4(x: np.ndarray, _ = None) -> np.ndarray:
x = np.atleast_2d(x)
return (
p_c(x) - 6000
)
# Objective functions
def f_1(x: np.ndarray) -> np.ndarray:
x = np.atleast_2d(x)
return (
1.10471 * x[:, 0]**2 * x[:, 1]
+ 0.04811 * x[:, 2] * x[:, 3] *
(14 + x[:, 1])
)
def f_2(x: np.ndarray) -> np.ndarray:
x = np.atleast_2d(x)
return (
(4 * 6000 * 14**3) /
(30 * 10**6 * x[:, 3] * x[:, 2]**3)
)
def f_3(x: np.ndarray) -> np.ndarray:
x = np.atleast_2d(x)
sum1 = g_1(x)
sum2 = g_2(x)
sum3 = g_3(x)
sum4 = g_4(x)
sum1 = np.where(sum1 > 0, sum1, 0)
sum2 = np.where(sum2 > 0, sum2, 0)
sum3 = np.where(sum3 > 0, sum3, 0)
sum4 = np.where(sum4 > 0, sum4, 0)
return sum1 + sum2 + sum3 + sum4
objective_1 = ScalarObjective(name="minimize cost of a welded beam", evaluator=f_1, maximize=[False])
objective_2 = ScalarObjective(name="minimize end deflection of a welded beam", evaluator=f_2, maximize=[False])
objective_3 = ScalarObjective(name="the sum of the four constraint violations", evaluator=f_3, maximize=[False])
objectives = [objective_1, objective_2, objective_3]
cons_1 = ScalarConstraint("c_1", 4, 3, g_1)
cons_2 = ScalarConstraint("c_2", 4, 3, g_2)
cons_3 = ScalarConstraint("c_3", 4, 3, g_3)
cons_4 = ScalarConstraint("c_4", 4, 3, g_4)
constraints = [cons_1, cons_2, cons_3, cons_4]
# Variables adjust the size of the beam
x_1 = Variable("x_1", 2.5, 0.125, 5)
x_2 = Variable("x_2", 5.0, 0.1, 10.0)
x_3 = Variable("x_3", 5.0, 0.1, 10.0)
x_4 = Variable("x_4", 2.5, 0.125, 5)
variables = [x_1, x_2, x_3, x_4]
problem = MOProblem(variables=variables, objectives=objectives, constraints=constraints)
return problem
[docs]def re33(var_iv: np.array = np.array([67.5, 92.5, 2000, 15])) -> MOProblem:
""" Disc brake design problem.
Arguments:
var_iv (np.array): Optional, initial variable values.
Defaults are [67.5, 92.5, 2000, 15]. x1 ∈ [55, 80],
x2 ∈ [75, 110], x3 ∈ [1000, 3000] and x4 ∈ [11, 20].
Returns:
MOProblem: a problem object.
"""
# Check the number of variables
if (np.shape(np.atleast_2d(var_iv)[0]) != (4,)):
raise RuntimeError("Number of variables must be four")
# Lower bounds
lb = np.array([55, 75, 1000, 11])
# Upper bounds
ub = np.array([80, 110, 3000, 20])
# Check the variable bounds
if np.any(lb > var_iv) or np.any(ub < var_iv):
raise ValueError("Initial variable values need to be between lower and upper bounds")
# Constrain functions
def g_1(x: np.ndarray, _ = None) -> np.ndarray:
x = np.atleast_2d(x)
return (
(x[:, 1] - x[:, 0]) - 20
)
def g_2(x: np.ndarray, _ = None) -> np.ndarray:
x = np.atleast_2d(x)
return (
0.4 - (x[:, 2] / (3.14 * (x[:, 1]**2 - x[:, 0]**2)))
)
def g_3(x: np.ndarray, _ = None) -> np.ndarray:
x = np.atleast_2d(x)
return (
1 - ((2.22 * 10**-3 * x[:, 2] * (x[:, 1]**3 - x[:, 0]**3)) /
(x[:, 1]**2 - x[:, 0]**2)**2)
)
def g_4(x: np.ndarray, _ = None) -> np.ndarray:
x = np.atleast_2d(x)
return (
((2.66 * 10**-2 * x[:, 2] * x[:, 3] * (x[:, 1]**3 - x[:, 0]**3)) /
(x[:, 1]**2 - x[:, 0]**2)) - 900
)
# Objective functions
def f_1(x: np.ndarray) -> np.ndarray:
x = np.atleast_2d(x)
return (
4.9 * 10**-5 * (x[:, 1]**2 - x[:, 0]**2) * (x[:, 3] -1)
)
def f_2(x: np.ndarray) -> np.ndarray:
x = np.atleast_2d(x)
return (
9.82 * 10**6 * ((x[:, 1]**2 - x[:, 0]**2) /
(x[:, 2] * x[:, 3] * (x[:, 1]**3 - x[:, 0]**3)))
)
def f_3(x: np.ndarray) -> np.ndarray:
x = np.atleast_2d(x)
sum1 = g_1(x)
sum2 = g_2(x)
sum3 = g_3(x)
sum4 = g_4(x)
sum1 = np.where(sum1 > 0, sum1, 0)
sum2 = np.where(sum2 > 0, sum2, 0)
sum3 = np.where(sum3 > 0, sum3, 0)
sum4 = np.where(sum4 > 0, sum4, 0)
return sum1 + sum2 + sum3 + sum4
objective_1 = ScalarObjective(name="minimize the mass of the brake", evaluator=f_1, maximize=[False])
objective_2 = ScalarObjective(name="the minimum stopping time", evaluator=f_2, maximize=[False])
objective_3 = ScalarObjective(name="the sum of the four constraint violations", evaluator=f_3, maximize=[False])
objectives = [objective_1, objective_2, objective_3]
cons_1 = ScalarConstraint("c_1", 4, 3, g_1)
cons_2 = ScalarConstraint("c_2", 4, 3, g_2)
cons_3 = ScalarConstraint("c_3", 4, 3, g_3)
cons_4 = ScalarConstraint("c_4", 4, 3, g_4)
constraints = [cons_1, cons_2, cons_3, cons_4]
x_1 = Variable("the inner radius of the discs", 67.5, 55, 80)
x_2 = Variable("the outer radius of the discs", 92.5, 75, 110)
x_3 = Variable("the engaging force", 2000, 1000, 3000)
x_4 = Variable("the number of friction surfaces", 15, 11, 20)
variables = [x_1, x_2, x_3, x_4]
problem = MOProblem(variables=variables, objectives=objectives, constraints=constraints)
return problem
