Installing Ipopt

example.py

# Example from https://jckantor.github.io/CBE30338/06.99-Pyomo-Examples.html
import pyomo.environ as pyo

V = 40     # liters
kA = 0.5   # 1/min
kB = 0.1   # l/min
CAf = 2.0  # moles/liter

# create a model instance
model = pyo.ConcreteModel()

# create x and y variables in the model
model.q = pyo.Var()

# add a model objective
model.objective = pyo.Objective(expr = model.q*V*kA*CAf/(model.q + V*kB)/(model.q + V*kA), sense=pyo.maximize)

# compute a solution using ipopt for nonlinear optimization
results =pyo.SolverFactory('ipopt').solve(model)
model.pprint()


# print solutions
qmax = model.q()
CBmax = model.objective()
print('\nFlowrate at maximum CB = ', qmax, 'liters per minute.')
print('\nMaximum CB =', CBmax, 'moles per liter.')
print('\nProductivity = ', qmax*CBmax, 'moles per minute.')

expected_output.txt

1 Var Declarations
    q : Size=1, Index=None
        Key  : Lower : Value             : Upper : Fixed : Stale : Domain
        None :  None : 8.944271909985442 :  None : False : False :  Reals

1 Objective Declarations
    objective : Size=1, Index=None, Active=True
        Key  : Active : Sense    : Expression
        None :   True : maximize : 40.0*q/(q + 4.0)/(q + 20.0)

2 Declarations: q objective

Flowrate at maximum CB =  8.944271909985442 liters per minute.

Maximum CB = 0.954915028125263 moles per liter.

Productivity =  8.541019662483748 moles per minute.

Ipopt.md

Installing Ipopt

https://coin-or.github.io/Ipopt/INSTALL.html

• ASL is required to use Ipopt from Pyomo
• I likely already had BLAS/LAPACK installed from other projects, I don't know if my libraries are optimised.

# Install dependencies
sudo apt-get install gcc g++ gfortran git patch wget pkg-config liblapack-dev libmetis-dev

# Install ASL
git clone https://github.com/coin-or-tools/ThirdParty-ASL.git
cd ThirdParty-ASL
./get.ASL
./configure
make
sudo make install

# Install MUMPS
git clone https://github.com/coin-or-tools/ThirdParty-Mumps.git
cd ThirdParty-Mumps
./get.Mumps
./configure
make
sudo make install

Download Ipopt source from here: https://github.com/coin-or/Ipopt/releases eg. Source code (tar.gz)

# Install Ipopt
gunzip Ipopt-x.y.z.tgz
tar xvf Ipopt-x.y.z.tar
mv Ipopt-x.y.z Ipopt
cd Ipopt
export IPOPTDIR=/path/to/currentdir

mkdir $IPOPTDIR/build
cd $IPOPTDIR/build
$IPOPTDIR/configure
make
make test
sudo make install

You may need to run sudo ldconfig after these steps - it's not specified anywhere, until I found this my solver failed with the following error message:

ERROR: Solver (ipopt) returned non-zero return code (127)
ERROR: Solver log: /usr/local/bin/ipopt: error while loading shared libraries:
libipoptamplinterface.so.3: cannot open shared object file: No such file or
directory

You can check the exit codes for any steps after running them by using echo $?. 0 means success, anything else is an error.

https://www.coin-or.org/Bonmin/Intro.html
https://www.scipopt.org/