Retrieve Solver Log Files in AIMMS Developer

Solvers can share information about the solution process up to a very detailed level. To avoid overhead in generating information that is not inspected anyway, the AIMMS IDE defaults to not sharing any information.

Get started with log files

The first option is to set the option solver_listing_messages to all. By just setting this option, a solver will generate a small log file with the name <solver name>.sta in the folder log. The first solve of an AIMMS session will create the file, subsequent solves will append to the file. To generate a log file, we used the Flow Shop example with 14 jobs and 20 machines and solved it using CPLEX 12.8 on my desktop.

Solve problem 'FlowShopModel' with 554 rows, 476 columns (196 binaries, 0 generals), and 8808 nonzeros.

MIP - Integer optimal solution:  Objective = 3.8900000000e+002
Solution time = 71.72 sec.  Iterations = 6163443  Nodes = 101990

Additional information and example

For a MIP problem, a typical first setting to add is the option MIP display to Display each nth node. Thus I obtained a 95 line log file log\cplex 12.8.sta. For the sake of brevity, I only show the first and last five lines here.

Solve problem 'FlowShopModel' with 554 rows, 476 columns (196 binaries, 0 generals), and 8808 nonzeros.
Tried aggregator 3 times.
MIP Presolve eliminated 0 rows and 1 columns.
MIP Presolve modified 7561 coefficients.
Aggregator did 25 substitutions.

Last five lines:

                          ------------
Total (root+branch&cut) =   72.72 sec. (45534.38 ticks)

MIP - Integer optimal solution:  Objective = 3.8900000000e+002
Solution time = 72.72 sec.  Iterations = 6163443  Nodes = 101990

Overview of options to try out first for logging

This section presents, based on problem type and solver, a list of first options to be set for more information. This is not a list of options to improve performance, but a first step to obtain more information about the solution process so analysis of the solution process can be started.

LP Problems solved using Barrier

Solver	Option	Value
CPLEX	Barrier display	Normal
GUROBI	Output file	yes
CBC	Status File	File

LP Problems solved using SIMPLEX

Solver	Option	Value
CPLEX	Simplex display	At refactorizations
GUROBI	Output file	yes
CBC	Status File	File

MIP Problems

Solver	Option	Value
CPLEX	MIP display	Display each nth node
ODH-CPLEX	Status display	Yes
	MIP display	Display each nth node
GUROBI	Output file	yes
CBC	Status File	File

Note

For ODH-CPLEX, setting the option MIP display requires setting the option Status display to Yes.

NLP Problems

Solver	Option	Value
BARON	Keep results file	On
CONOPT	Status file display	Iteration log
IPOPT	Status file	Yes
KNITRO	Status file display	Summary
SNOPT	Print output file	On

Further reading

The interpretation of log files is discussed in:

• LP

• MIP