Unable to call Gurobi Solver from PuLP

[Akul Bansal]

I am using PuLP (version 1.6.8) on a Windows 10 64bit machine through Spyder (Anaconda) compiler. I have recently installed free academic licence of Gurobi and trying to call the gurobi solver from Pulp interface. On doing so I get the following error 

PermissionError: [WinError 5] Access is denied

These are following things I am doing and have tried to resolve the issue. I am a novice and everything below is hit and trial. 

1.  Called the gurobi solver in PuLP with command prob.solve(GUROBI_CMD("C:\gurobi801\win64"))

2. Ran Spyder with administrator permissions.

3. Reinstalled the gurobi licence file into different folders

4. Set path variable GRB_LICENSE_FILE with value C:\gurobi801\win64\gurobi.lic

5. Gave all read/write permissions to the gurobi folder

6. Installed general version of Python 3.7 (was only using spyder before)

7. Tried running the command prob.solve(GUROBI("C:\gurobi801\win64"))

8. Ran the command pulp.pulpTestAll and found GUROBI_CMD passed and rest were unavialable

9. Tried running following commands

#SS = solvers.GUROBI_CMD("C:\gurobi801\win64")

#SS.actualSolve(prob)

but still got same error

10. Changed path to  C:\gurobi801\ in above commands

11. Checked by running gurobi shell that license was running and installed

I basically want to have warm starts for MIPs thats why I want Gurobi. Any help would be appreciated.

Regards, Akul

[Stuart Mitchell]

Sounds like you need to follow these instructions

http://www.gurobi.com/documentation/8.0/quickstart_mac/the_gurobi_python_interfac.html

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[Akul Bansal]

Dear Stuart,

Thanks for replying back. I have separately downloaded gurobipy through anaconda prompt very similar to what is suggested on the page you shared. A few more things that I have tried are :

1. Putting the gurobi folder (including licence file) in the same folder where I have all my python files

2. Installing gurobi in D Drive

I am still getting the same error !

Are there any alternatives to warm starting while still using PuLP interface ? I don't want to rewrite everything again.

[Akul Bansal]

A small update, I have identified warm starts are different from giving an initial solution and CBC does allow setting up an initial solution. I haven't implemented this yet but more details can be found here 

https://groups.google.com/d/msg/pulp-or-discuss/-aiL7jQyD-k/MNgi2BEPCwAJ

Warm starts make more sense in the LP setting where the solver picks up the basic feasible solution given in warm start and sometimes also the inverse. 

[Stuart Mitchell]

from your python file can you do 

import gurobipy

if you can do this you can access the gurobi solver from python and in pulp the GUROBI() solver class should work

if not you need to follow the instructions on the gurobi website

Stu

Stuart Mitchell

PhD Engineering Science

Extraordinary Freelance Programmer and Optimisation Guru

www.stuartmitchell.com

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[Akul Bansal]

I am able to import gurobipy but I am passing the solver as GUROBI_CMD. When I do pulp.pulpTestAll this is the solver that comes "passed". Actually trying passing the solver GUROBI worked !! Thanks a lot. This is surprising as same thing was not working before!