test_functions/SpeedReducer.py

import torch
import numpy as np

#
#
#   SpeedReducer: 7D objective, 9 constraints
#
#   Reference:
#     Yang XS, Hossein Gandomi A (2012) Bat algo-
#      rithm: a novel approach for global engineer-
#      ing optimization. Engineering computations
#      29(5):464–483
#
#

def SpeedReducer(individuals): 

    assert torch.is_tensor(individuals) and individuals.size(1) == 7, "Input must be an n-by-7 PyTorch tensor."
    
    fx = []
    gx1 = []
    gx2 = []
    gx3 = []
    gx4 = []
    gx5 = []
    gx6 = []
    gx7 = []
    gx8 = []
    gx9 = []
    gx10 = []
    gx11 = []
    
    

    n = individuals.size(0)
    
    for i in range(n):
        
        x = individuals[i,:]

        
        b = x[0]
        m = x[1]
        z = x[2]
        L1 = x[3]
        L2 = x[4]
        d1 = x[5]
        d2 = x[6]
        
        C1 = 0.7854*b*m*m
        C2 = 3.3333*z*z + 14.9334*z - 43.0934
        C3 = 1.508*b*(d1*d1 + d2*d2)
        C4 = 7.4777*(d1*d1*d1 + d2*d2*d2)
        C5 = 0.7854*(L1*d1*d1 + L2*d2*d2)
        
        
        ## Negative sign to make it a maximization problem
        test_function = - ( 0.7854*b*m*m * (3.3333*z*z + 14.9334*z - 43.0934) - 1.508*b*(d1*d1 + d2*d2) + 7.4777*(d1*d1*d1 + d2*d2*d2) + 0.7854*(L1*d1*d1 + L2*d2*d2)  )

        fx.append(test_function) 
        
        ## Calculate constraints terms 
        g1 = 27/(b*m*m*z) - 1
        g2 = 397.5/(b*m*m*z*z) - 1

        g3 = 1.93*L1**3 /(m*z *d1**4) - 1
        g4 = 1.93*L2**3 /(m*z *d2**4) - 1

        g5 = np.sqrt( (745*L1/(m*z))**2 + 1.69*1e6 ) / (110*d1**3) -1
        g6 = np.sqrt( (745*L2/(m*z))**2 + 157.5*1e6 ) / (85*d2**3) -1
        g7 = m*z/40 - 1
        g8 = 5*m/(b) - 1
        g9 = b/(12*m) -1



        gx1.append( g1 )       
        gx2.append( g2 )    
        gx3.append( g3 )            
        gx4.append( g4 )
        gx5.append( g5 )       
        gx6.append( g6 )    
        gx7.append( g7 )            
        gx8.append( g8 )
        gx9.append( g9 )


    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))
    
    gx5 = torch.tensor(gx5)  
    gx5 = gx1.reshape((n, 1))

    gx6 = torch.tensor(gx6)  
    gx6 = gx2.reshape((n, 1))
    
    gx7 = torch.tensor(gx7)  
    gx7 = gx3.reshape((n, 1))
    
    gx8 = torch.tensor(gx8)  
    gx8 = gx4.reshape((n, 1))
    
    gx9 = torch.tensor(gx9)  
    gx9 = gx4.reshape((n, 1))

    gx = torch.cat((gx1, gx2, gx3, gx4, gx5, gx6, gx7, gx8, gx9), 1)

    
    return gx, fx



def SpeedReducer_Scaling(X):

    assert torch.is_tensor(X) and X.size(1) == 7, "Input must be an n-by-7 PyTorch tensor."

    b  = (X[:,0] * ( 3.6 - 2.6 ) + 2.6).reshape(X.shape[0],1)
    m  = (X[:,1] * ( 0.8 - 0.7 ) + 0.7).reshape(X.shape[0],1)
    z  = (X[:,2] * ( 28 - 17 ) + 17).reshape(X.shape[0],1)
    L1 = (X[:,3] * ( 8.3 - 7.3 ) + 7.3).reshape(X.shape[0],1)
    L2 = (X[:,4] * ( 8.3 - 7.3 ) + 7.3).reshape(X.shape[0],1)
    d1 = (X[:,5] * ( 3.9 - 2.9 ) + 2.9).reshape(X.shape[0],1)
    d2 = (X[:,6] * ( 5.5 - 5 ) + 5).reshape(X.shape[0],1)
    
    X_scaled = torch.cat((b, m, z, L1, L2, d1, d2), dim=1)
    return X_scaled