How to make the IPOPT solver silent in with Opti in Python

[Shima Nazari]

Hi, 

I am using casadi.Opti in python with IPOPT solver for an MPC problem. 

I am using the following piece of code to assign a solver and change printing level:

opts = dict(print_time=False, verbose=False)

opti.solver("ipopt",opts)

However, still the solver prints too much information about its iterations. When I try print_iteration=False, or print_iter=False, I get an error of "unknown option". 

Does any body know how to make the solver completely silent in python?

Thank you

Shima

[Aaron Ray]

I believe you need something like:

p_opts = dict(print_time=False, verbose=False)

s_opts = dict(print_level=0)

opti.solver("ipopt", p_opts, s_opts)

The two sets of options are discussed here: https://web.casadi.org/docs/#problem-specification

The options that you can set for ipopt are here: http://casadi.sourceforge.net/v2.0.0/api/html/d6/d07/classcasadi_1_1NlpSolver.html

(I've only worked with the Casadi NlpSolver interfance and not Opti, but I think the ipopt options are the same).

[Chris Mower]

Hi,

To completely silence the solver you can set 

opts = {'ipopt.print_level': 0, 'print_time': 0, 'ipopt.sb': 'yes'}

opti.solver('ipopt', opts)

However, I find having access to the solver output is useful when debugging and instead I re-direct the stdout to a file before calling opti.solve(). You can do this in the following way:

import sys

import traceback

import casadi as ca

opti = ca.Opti()

# Setup opti problem ...

with open('solver_output.txt', 'w') as output_file:

    # Retrieve default stdout

    stdout_old = sys.stdout

    # Re-direct standard output

    sys.stdout = output_file

    try:

        opti.solve()

     except:

         # If error thrown -> print exception to old stdout

         traceback.print_exc(file=stdout_old)

     finally:

         # Re-direct stdout to default

         sys.stdout = stdout_old

Hope this helps!

Best,

Chris