Hi everyone.

I’m trying to set up tests for a project on Travis which uses JuMP with the Ipopt solver (repo for the project is here).

The build steps seem fine as far as I can tell and my tests can run (well, sometimes at least). However, the optimisation turns out to be infeasible in this environment, but not on my local machines.

Here is a link to a build log that’s infeasible, and another which just seems to spool forever.

Compare this with the output of the two problematic tests locally:

```
Total number of variables............................: 1561
variables with only lower bounds: 540
variables with lower and upper bounds: 180
variables with only upper bounds: 120
Total number of equality constraints.................: 1391
Total number of inequality constraints...............: 59
inequality constraints with only lower bounds: 0
inequality constraints with lower and upper bounds: 0
inequality constraints with only upper bounds: 59
Number of Iterations....: 142
(scaled) (unscaled)
Objective...............: -2.6702779245830361e+03 -2.6702779245830361e+03
Dual infeasibility......: 5.6843418860808015e-14 5.6843418860808015e-14
Constraint violation....: 3.9348429028973619e-11 3.9348429028973619e-11
Complementarity.........: 2.5059035671809955e-09 2.5059035671809955e-09
Overall NLP error.......: 2.5059035671809955e-09 2.5059035671809955e-09
Number of objective function evaluations = 148
Number of objective gradient evaluations = 108
Number of equality constraint evaluations = 148
Number of inequality constraint evaluations = 148
Number of equality constraint Jacobian evaluations = 144
Number of inequality constraint Jacobian evaluations = 144
Number of Lagrangian Hessian evaluations = 142
Total CPU secs in IPOPT (w/o function evaluations) = 11.215
Total CPU secs in NLP function evaluations = 1.649
EXIT: Optimal Solution Found.
Total number of variables............................: 1561
variables with only lower bounds: 540
variables with lower and upper bounds: 180
variables with only upper bounds: 120
Total number of equality constraints.................: 1391
Total number of inequality constraints...............: 59
inequality constraints with only lower bounds: 0
inequality constraints with lower and upper bounds: 0
inequality constraints with only upper bounds: 59
Number of Iterations....: 32
(scaled) (unscaled)
Objective...............: -2.6702779245830334e+03 -2.6702779245830334e+03
Dual infeasibility......: 5.6843418860808015e-14 5.6843418860808015e-14
Constraint violation....: 3.9348409947015384e-11 3.9348409947015384e-11
Complementarity.........: 2.5059035671809955e-09 2.5059035671809955e-09
Overall NLP error.......: 2.5059035671809955e-09 2.5059035671809955e-09
Number of objective function evaluations = 33
Number of objective gradient evaluations = 33
Number of equality constraint evaluations = 33
Number of inequality constraint evaluations = 33
Number of equality constraint Jacobian evaluations = 33
Number of inequality constraint Jacobian evaluations = 33
Number of Lagrangian Hessian evaluations = 32
Total CPU secs in IPOPT (w/o function evaluations) = 1.817
Total CPU secs in NLP function evaluations = 0.351
EXIT: Optimal Solution Found.
Total number of variables............................: 1561
variables with only lower bounds: 540
variables with lower and upper bounds: 180
variables with only upper bounds: 120
Total number of equality constraints.................: 1391
Total number of inequality constraints...............: 59
inequality constraints with only lower bounds: 0
inequality constraints with lower and upper bounds: 0
inequality constraints with only upper bounds: 59
Number of Iterations....: 32
(scaled) (unscaled)
Objective...............: -2.6702779245830334e+03 -2.6702779245830334e+03
Dual infeasibility......: 2.8421709430404007e-14 2.8421709430404007e-14
Constraint violation....: 3.9348409947015384e-11 3.9348409947015384e-11
Complementarity.........: 2.5059035671809955e-09 2.5059035671809955e-09
Overall NLP error.......: 2.5059035671809955e-09 2.5059035671809955e-09
Number of objective function evaluations = 33
Number of objective gradient evaluations = 33
Number of equality constraint evaluations = 33
Number of inequality constraint evaluations = 33
Number of equality constraint Jacobian evaluations = 33
Number of inequality constraint Jacobian evaluations = 33
Number of Lagrangian Hessian evaluations = 32
Total CPU secs in IPOPT (w/o function evaluations) = 1.996
Total CPU secs in NLP function evaluations = 0.393
EXIT: Optimal Solution Found.
Total number of variables............................: 1561
variables with only lower bounds: 540
variables with lower and upper bounds: 180
variables with only upper bounds: 76
Total number of equality constraints.................: 1391
Total number of inequality constraints...............: 59
inequality constraints with only lower bounds: 0
inequality constraints with lower and upper bounds: 0
inequality constraints with only upper bounds: 59
Number of Iterations....: 260
(scaled) (unscaled)
Objective...............: -2.6902447324365826e+03 -2.6902447324365826e+03
Dual infeasibility......: 5.6843418860808015e-14 5.6843418860808015e-14
Constraint violation....: 4.3934286764191199e-11 4.0218033681149734e-08
Complementarity.........: 2.5059035743924103e-09 2.5059035743924103e-09
Overall NLP error.......: 2.5059035743924103e-09 4.0218033681149734e-08
Number of objective function evaluations = 294
Number of objective gradient evaluations = 228
Number of equality constraint evaluations = 294
Number of inequality constraint evaluations = 294
Number of equality constraint Jacobian evaluations = 263
Number of inequality constraint Jacobian evaluations = 263
Number of Lagrangian Hessian evaluations = 260
Total CPU secs in IPOPT (w/o function evaluations) = 20.503
Total CPU secs in NLP function evaluations = 2.698
EXIT: Optimal Solution Found.
Total number of variables............................: 1561
variables with only lower bounds: 540
variables with lower and upper bounds: 180
variables with only upper bounds: 76
Total number of equality constraints.................: 1391
Total number of inequality constraints...............: 59
inequality constraints with only lower bounds: 0
inequality constraints with lower and upper bounds: 0
inequality constraints with only upper bounds: 59
Number of Iterations....: 32
(scaled) (unscaled)
Objective...............: -2.6902447128731592e+03 -2.6902447128731592e+03
Dual infeasibility......: 5.6843418860808015e-14 5.6843418860808015e-14
Constraint violation....: 4.3934286764191199e-11 4.3934286764191199e-11
Complementarity.........: 2.5059035743924124e-09 2.5059035743924124e-09
Overall NLP error.......: 2.5059035743924124e-09 2.5059035743924124e-09
Number of objective function evaluations = 33
Number of objective gradient evaluations = 33
Number of equality constraint evaluations = 33
Number of inequality constraint evaluations = 33
Number of equality constraint Jacobian evaluations = 33
Number of inequality constraint Jacobian evaluations = 33
Number of Lagrangian Hessian evaluations = 32
Total CPU secs in IPOPT (w/o function evaluations) = 2.099
Total CPU secs in NLP function evaluations = 0.317
EXIT: Optimal Solution Found.
Total number of variables............................: 1561
variables with only lower bounds: 540
variables with lower and upper bounds: 180
variables with only upper bounds: 76
Total number of equality constraints.................: 1391
Total number of inequality constraints...............: 59
inequality constraints with only lower bounds: 0
inequality constraints with lower and upper bounds: 0
inequality constraints with only upper bounds: 59
Number of Iterations....: 32
(scaled) (unscaled)
Objective...............: -2.6902447128731592e+03 -2.6902447128731592e+03
Dual infeasibility......: 2.8421709430404007e-14 2.8421709430404007e-14
Constraint violation....: 4.3934290233638151e-11 4.3934290233638151e-11
Complementarity.........: 2.5059035743924120e-09 2.5059035743924120e-09
Overall NLP error.......: 2.5059035743924120e-09 2.5059035743924120e-09
Number of objective function evaluations = 33
Number of objective gradient evaluations = 33
Number of equality constraint evaluations = 33
Number of inequality constraint evaluations = 33
Number of equality constraint Jacobian evaluations = 33
Number of inequality constraint Jacobian evaluations = 33
Number of Lagrangian Hessian evaluations = 32
Total CPU secs in IPOPT (w/o function evaluations) = 2.080
Total CPU secs in NLP function evaluations = 0.300
EXIT: Optimal Solution Found.
Test Summary: | Pass Total
Utility | 2 2
INFO: DICE tests passed
```

I’m using Arch Linux locally, and Travis uses Debian by default.

Does anyone know how I could start to troubleshoot this issue? It must have something to do with my environment setup on the Travis side, but without any specific error to chase down I’m a bit stuck.