Path Error when running Gekko Optimization Solver

Question

Running the attached code results in the below error. The error is the same even if changing m.options.SOLVER to 2 or 3

Traceback (most recent call last): File "C:\Users\17576\Documents\Python\Scratch.py", line 33, in m.solve() File "C:\Users\17576\Documents\Python\venv\lib\site-packages\gekko\gekko.py", line 2227, in solve self.load_JSON() File "C:\Users\17576\Documents\Python\venv\lib\site-packages\gekko\gk_post_solve.py", line 13, in load_JSON f = open(os.path.join(self._path,'options.json')) FileNotFoundError: [Errno 2] No such file or directory: 'C:\Users\17576\AppData\Local\Temp\tmpp6w85mm5gk_model0\options.json'

Error: The system cannot find the path specified.

Error: 'results.json' not found. Check above for additional error details

Process finished with exit code 1

from gekko import GEKKO

# Variables
var_a = 155.31
var_b = 6.27
var_c = 12
var_d = 750
var_e = 10
var_f = 1
var_d_lower_bound_percentage = .99
var_e_lower_bound_percentage = .99
var_e_upper_bound_percentage = 1.01
x_value = 1
y_value = 3

# Optimization
m = GEKKO(remote=False)

x = m.Var(value=x_value, lb=0)
y = m.Var(value=y_value, lb=0, integer=True)

m.Equation(x*var_a + y*var_b <= var_d)
m.Equation(x*var_a + y*var_b >= var_d*var_d_lower_bound_percentage)

m.Equation(((x*var_a)/(x*var_a + y*var_b)) + ((y*var_b)/(x*var_a + y*var_b)) == 1)

m.Equation(((x*var_a)/(x*var_a + y*var_b))*var_f + ((y*var_b)/(x*var_a + y*var_b))*var_c <= var_e*var_e_upper_bound_percentage)
m.Equation(((x*var_a)/(x*var_a + y*var_b))*var_f + ((y*var_b)/(x*var_a + y*var_b))*var_c >= var_e*var_e_lower_bound_percentage)

m.Obj(((x*var_a)/(x*var_a + y*var_b))*var_f + ((y*var_b)/(x*var_a + y*var_b))*var_c)

m.options.SOLVER = 1
m.solve()

print(x.value)
print(y.value)

Answer 1

Try upgrading the version of gekko . See instructions on managing packages if additional support is needed.

pip install gekko --upgrade

Both remote and local solutions complete successfully with gekko version 1.0.5. From the path error, it appears that it is either an older version or else there is a permission error with writing to the tmp run directory folder on your Windows computer.

 ----------------------------------------------------------------
 APMonitor, Version 1.0.0
 APMonitor Optimization Suite
 ----------------------------------------------------------------
 --------- APM Model Size ------------
 Each time step contains
   Objects      :  0
   Constants    :  0
   Variables    :  6
   Intermediates:  0
   Connections  :  0
   Equations    :  6
   Residuals    :  6
 
 Number of state variables:    6
 Number of total equations: -  5
 Number of slack variables: -  4
 ---------------------------------------
 Degrees of freedom       :    -3
 
 * Warning: DOF <= 0
 ----------------------------------------------
 Steady State Optimization with APOPT Solver
 ----------------------------------------------
Iter:     1 I:  0 Tm:      0.00 NLPi:    5 Dpth:    0 Lvs:    2 Obj:  9.90E+00 Gap:       NaN
--Integer Solution:   9.90E+00 Lowest Leaf:   9.90E+00 Gap:   0.00E+00
Iter:     2 I:  0 Tm:      0.00 NLPi:    5 Dpth:    1 Lvs:    2 Obj:  9.90E+00 Gap:  0.00E+00
 Successful solution
 
 ---------------------------------------------------
 Solver         :  APOPT (v1.0)
 Solution time  :  0.0156 sec
 Objective      :  9.9
 Successful solution
 ---------------------------------------------------

[0.91446827259]
[96.0]