使用Pyomo调用CBC求解器：.sol文件写入及文件名获取问题

Let’s break down practical solutions to your questions, tailored for Jupyter Notebook environments:

1. Writing Solver Results to a .sol File & Getting the Filename #

You have two reliable approaches, depending on whether you want a custom filename or need to retrieve Pyomo’s auto-generated temporary file:

Option A: Specify a Custom Filename Explicitly #

Use CBC’s built-in solution file option (either solution or solu as the option name) when configuring the solver. Make sure to set the option before calling solve():

from pyomo.environ import ConcreteModel, SolverFactory

# Create your model (example placeholder)
model = ConcreteModel()
# ... add variables, constraints, objective ...

# Configure solver with custom solution file
solver = SolverFactory('cbc')
solver.options['solution'] = 'my_custom_solution.sol'  # Or use 'solu' as shorthand

# Solve the model
result = solver.solve(model)

# The filename is the one you specified
print(f"Solution written to: my_custom_solution.sol")

If you prefer a solver-agnostic method (works across all Pyomo-supported solvers), use the result object to write the file after solving:

# Write solution to file using the result object
result.write(filename='my_custom_solution.sol', format='sol')

Option B: Retrieve Auto-Generated .sol Filename (with keepfiles=True) #

When you set keepfiles=True, Pyomo creates temporary files (including the .sol file) in a system temp directory. To get the exact path of this auto-generated file, access the solver’s solutions attribute after solving:

solver = SolverFactory('cbc')
result = solver.solve(model, keepfiles=True)

# Get the full path to the auto-generated .sol file
auto_sol_filename = solver.solutions[0].filename
print(f"Auto-generated solution file: {auto_sol_filename}")

2. Fixing the "No .sol File Generated" Issue in Jupyter Notebook #

Your attempt to use solver.options['solu']="solution_file.sol" likely failed due to one of these common issues, with easy fixes:

Fix 1: Reuse the Same Solver Instance #

Avoid chaining calls in one line—this creates a fresh solver instance each time, losing your option settings:

# ❌ Wrong: Creates two separate solver instances
SolverFactory("cbc").options['solu']="solution_file.sol"
SolverFactory("cbc").solve(model)

# ✅ Correct: Reuse the same solver instance
solver = SolverFactory("cbc")
solver.options['solu'] = "solution_file.sol"
solver.solve(model)

Fix 2: Fall Back to the Result Write Method #

If the solver option approach still doesn’t work, use Pyomo’s result object to write the solution. This method is consistently reliable in Jupyter:

result = solver.solve(model)
# Write the solution to a .sol file
result.write(filename='solution_file.sol', format='sol')

Fix 3: Verify CBC Accessibility #

In rare cases, CBC might not be properly installed or in your system PATH. Confirm it’s accessible with:

solver = SolverFactory('cbc')
print(solver.available())  # Should return True

内容的提问来源于stack exchange，提问作者Hussain K