Can someone fix my python code & docplex?

Question

I have to do a python code for a project but when i run it, i have a problem with it. I try to fix it but it's always the same problem. It said the same code error...

this is my code

from docplex.mp.model import Model
m=Model(name="bedford")
X1=m.continuous_var(name='Ashley')
X2=m.continuous_var(name='Bedford')
X3=m.continuous_var(name='Cosnol')
X4=m.continuous_var(name='Dunby')
X5=m.continuous_var(name='Earlam')
X6=m.continuous_var(name='Florence')
X7=m.continuous_var(name='Gaston')
X8=m.continuous_var(name='Hopt')
#average volatility
avgvol=19
#volatility constraint
Volatility=m.add_constraint((15-avgvol)*X1+ 
                            (16-avgvol)*X2+ 
                            (18-avgvol)*X3+ 
                            (20-avgvol)*X4+ 
                            (21-avgvol)*X5+ 
                            (22-avgvol)*X6+ 
                            (23-avgvol)*X7+ 
                            (24-avgvol)*X8 
                            >=0,"volatility_constraint"
                           )
#Capacity constraint
Supply=m.add_constraint(X1+X2+X3+X4+X5+X6+X7+X8==1225,"Supply")
#Rail, Truck & Union constraints
Truck=m.add_constraint(X2+X4+X5+X6==720,"Truck")
Rail=m.add_constraint(X1+X3+X7+X8==650,"Rail")
Union=m.add_constraint(X1+X2-X3+X4-X5+X6-X7-X8>=0,"Union")
#Constraints
Ashley=m.add_constraint(X1<= 300,"Ashley")
Bedford=m.add_constraint(X2<= 600,"Bedford")
Cosnol=m.add_constraint(X3<= 500,"Cosnol")
Dunby=m.add_constraint(X4<= 655,"Dunby")
Earlam=m.add_constraint(X5<= 575,"Earlam")
Florence=m.add_constraint(X6<= 680,"Florence")
Gaston=m.add_constraint(X7<= 450,"Gaston")
Hopt=m.add_constraint(X8<=490,"Hopt")
m.minimize(X1*49.5+X2*50+X3*61+X4*63.5+X5*66.5+X6*71+X7*72.5+X8*80)
m.print_information()
s=m.solve()
m.print_solution()

and the error code: I tried to understand but at the final it's always the same problem, I need a help of someone

DOcplexException                          Traceback (most recent call last)
Input In [6], in <cell line: 49>()
     47 m.print_information()
     48 s=m.solve()
---> 49 m.print_solution()
File ~/opt/anaconda3/lib/python3.9/site-packages/docplex/mp/model.py:6081, in         Model.print_solution(self, print_zeros, solution_header_fmt, var_value_fmt, **kwargs)
   6063 def print_solution(self, print_zeros=False,
   6064                    solution_header_fmt=None,
   6065                    var_value_fmt=None,
   6066                    **kwargs):
   6067     """  Prints the values of the model variables after a solve.
   6068 
   6069     Only valid after a successful solve. If the model has not been solved successfully, an
   (...)
   6079         :func:`docplex.mp.solution.SolveSolution.display`
   6080     """
-> 6081     self._check_has_solution()
   6082     if var_value_fmt is None:
   6083         if self._has_username_with_spaces():
File ~/opt/anaconda3/lib/python3.9/site-packages/docplex/mp/model.py:5189, in     Model._check_has_solution(self)
   5187     self.fatal("Model<{0}> has not been solved yet", self.name)
   5188 else:
-> 5189     self.fatal("Model<{0}> did not solve successfully", self.name)
File ~/opt/anaconda3/lib/python3.9/site-packages/docplex/mp/model.py:1080, in Model.fatal(self, msg, *args)
   1079 def fatal(self, msg, *args):
-> 1080     self._error_handler.fatal(msg, args)
File ~/opt/anaconda3/lib/python3.9/site-packages/docplex/mp/error_handler.py:210, in AbstractErrorHandler.fatal(self, msg, args)
    208 resolved_message = resolve_pattern(msg, args)
    209 docplex_error_stop_here()
--> 210 raise DOcplexException(resolved_message)
DOcplexException: Model<bedford> did not solve successfully

It doesn't work, the attribute error is 'NoneType' object has no attribute 'print_solution' @MatBailie — Theo GUIRROU, Feb 23 '23 at 11:36
The documentation says that None is returned by Solve if there is no solution (or an error if you try to print solution). What makes you ***certain*** that, for your constraints, a solution actually ***exists***? — MatBailie, Feb 23 '23 at 11:36
Then show the full and exact parameters you used in excel solver, and the solution it gave. Because it seems highly likely that one or more of the constraints don't match. — MatBailie, Feb 23 '23 at 11:41
People won't follow links to filesharing. It's just asking to get infected with something. Please add everything as formatted texts or embedded images to your question. [ask] — MatBailie, Feb 23 '23 at 12:07

Alex Fleischer · Accepted Answer · 2023-02-23T13:51:42.723

if you ask for the log in

m.solve(log_output=True)

then you will get

Row 'Supply' is dependent and infeasible.

And then if you remove

Supply=m.add_constraint(X1+X2+X3+X4+X5+X6+X7+X8==1225,"Supply")

you will get a solution

objective: 82353.000
  Ashley=200.000
  Bedford=488.000
  Earlam=232.000
  Gaston=450.000

If you sant to see conflicts like in https://github.com/AlexFleischerParis/zoodocplex/blob/master/zoorelaxationandconflict.py

from docplex.mp.model import Model
from docplex.mp.conflict_refiner import ConflictRefiner

m=Model(name="bedford")
X1=m.continuous_var(name='Ashley')
X2=m.continuous_var(name='Bedford')
X3=m.continuous_var(name='Cosnol')
X4=m.continuous_var(name='Dunby')
X5=m.continuous_var(name='Earlam')
X6=m.continuous_var(name='Florence')
X7=m.continuous_var(name='Gaston')
X8=m.continuous_var(name='Hopt')
#average volatility
avgvol=19
#volatility constraint
Volatility=m.add_constraint((15-avgvol)*X1+ 
                            (16-avgvol)*X2+ 
                            (18-avgvol)*X3+ 
                            (20-avgvol)*X4+ 
                            (21-avgvol)*X5+ 
                            (22-avgvol)*X6+ 
                            (23-avgvol)*X7+ 
                            (24-avgvol)*X8 
                            >=0,"volatility_constraint"
                           )
#Capacity constraint
Supply=m.add_constraint(X1+X2+X3+X4+X5+X6+X7+X8==1225,"Supply")
#Rail, Truck & Union constraints
Truck=m.add_constraint(X2+X4+X5+X6==720,"Truck")
Rail=m.add_constraint(X1+X3+X7+X8==650,"Rail")
Union=m.add_constraint(X1+X2-X3+X4-X5+X6-X7-X8>=0,"Union")
#Constraints
Ashley=m.add_constraint(X1<= 300,"Ashley")
Bedford=m.add_constraint(X2<= 600,"Bedford")
Cosnol=m.add_constraint(X3<= 500,"Cosnol")
Dunby=m.add_constraint(X4<= 655,"Dunby")
Earlam=m.add_constraint(X5<= 575,"Earlam")
Florence=m.add_constraint(X6<= 680,"Florence")
Gaston=m.add_constraint(X7<= 450,"Gaston")
Hopt=m.add_constraint(X8<=490,"Hopt")
m.minimize(X1*49.5+X2*50+X3*61+X4*63.5+X5*66.5+X6*71+X7*72.5+X8*80)
m.print_information()
#m.solve(log_output=True)

cr=ConflictRefiner()
conflicts=cr.refine_conflict(m)
conflicts.display()
m.print_solution()

and you will get

conflict(s): 3
  - status: Member, LinearConstraint: Supply: Ashley + Bedford + Cosnol + Dunby + Earlam + Flo.. == 1225
  - status: Member, LinearConstraint: Truck: Bedford + Dunby + Earlam + Florence == 720
  - status: Member, LinearConstraint: Rail: Ashley + Cosnol + Gaston + Hopt == 650

Ok thanks, it's working when i did that but the problem is i need it for a constraint — Theo GUIRROU, Feb 23 '23 at 13:38
Then you should comment another constraint. #Truck=m.add_constraint(X2+X4+X5+X6==720,"Truck") — Alex Fleischer, Feb 23 '23 at 13:46
Ok ok ok Thanks a lot !!!!! I have another error ! Now its working ! It's about truck, its not == it's <=720. and its <= 650. So thanks a lot !!!!! — Theo GUIRROU, Feb 23 '23 at 13:53

Can someone fix my python code & docplex?

this is my code

1 Answers1