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import torch
import numpy as np
#
#
# PressureVessel: 4D objective, 4 constraints
#
# Reference:
# Gandomi AH, Yang XS, Alavi AH (2011) Mixed
# variable structural optimization using firefly
# algorithm. Computers & Structures 89(23-
# 24):2325–2336
#
#
def PressureVessel(individuals):
assert torch.is_tensor(individuals) and individuals.size(1) == 4, "Input must be an n-by-4 PyTorch tensor."
C1 = 0.6224
C2 = 1.7781
C3 = 3.1661
C4 = 19.84
fx = []
gx1 = []
gx2 = []
gx3 = []
gx4 = []
n = individuals.size(0)
for i in range(n):
x = individuals[i,:]
# print(x)
Ts = x[0]
Th = x[1]
R = x[2]
L = x[3]
## Negative sign to make it a maximization problem
test_function = - ( C1*Ts*R*L + C2*Th*R*R + C3*Ts*Ts*L + C4*Ts*Ts*R )
fx.append(test_function)
g1 = -Ts + 0.0193*R
g2 = -Th + 0.00954*R
g3 = (-1)*np.pi*R*R*L + (-1)*4/3*np.pi*R*R*R + 750*1728
g4 = L-240
gx1.append( g1 )
gx2.append( g2 )
gx3.append( g3 )
gx4.append( g4 )
fx = torch.tensor(fx)
fx = torch.reshape(fx, (len(fx),1))
gx1 = torch.tensor(gx1)
gx1 = gx1.reshape((n, 1))
gx2 = torch.tensor(gx2)
gx2 = gx2.reshape((n, 1))
gx3 = torch.tensor(gx3)
gx3 = gx3.reshape((n, 1))
gx4 = torch.tensor(gx4)
gx4 = gx4.reshape((n, 1))
gx = torch.cat((gx1, gx2, gx3, gx4), 1)
return gx, fx
def PressureVessel_Scaling(X):
assert torch.is_tensor(X) and X.size(1) == 4, "Input must be an n-by-4 PyTorch tensor."
Ts = (X[:,0] * (98*0.0625) + 0.0625).reshape(X.shape[0],1)
Th = (X[:,1] * (98*0.0625) + 0.0625).reshape(X.shape[0],1)
R = (X[:,2] * (200-10) + 10).reshape(X.shape[0],1)
L = (X[:,3] * (200-10) ).reshape(X.shape[0],1)
X_scaled = torch.cat((Ts, Th, R, L), dim=1)
return X_scaled
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