Solver (bonmin) not available

[javierbp00]

Hello everyone!

When I try to run the RBFOPT algorithm, everything seems to work normally. However, after a few seconds, the "ApplicationError: Solver (bonmin) not available" appears.

Why is is that? Any solutions? Thanks!

[gnannicini]

Hello,
it looks like the bonmin executable was not found. Did you try to install bonmin in your path? Please read the installation instructions.
If bonmin is not in your path, you can provide the path as explained in the readme and user guide.

[javierbp00]

Hi! Thanks for answering! I already fixed it. It was for that reason, I didn't have the path put in a correct way

[javierbp00]

already fixed it. It was for that reason, I didn't have the path put in a correct way

Thanks!

[gnannicini]

You can try print_solver_output=True to show (rather than suppress, which is the default) whatever the solver wants to print out. This way you can try to determine if bonmin is successfully executed or not. Keep in mind that both bonmin and ipopt are used, but which one is used changes depending on the iteration and the global_search_method parameter; setting global_search_method='solver' will use the solvers at every iteration, in particular if you have integer variables then bonmin will be used in every iteration.

It's extremely surprising that bonmin would work for some ~100 iterations and then say "not available", hence I recommend you check whether it's working at all.

[Florent-H]

bonmin 1.8.9 appears to correctly load during the first 100 to 200 iterations. Here is an example output of the solver:

Bonmin 1.8.9 using Cbc 2.10.8 and Ipopt 3.12.13
bonmin: bonmin.num_resolve_at_root=10
bonmin.num_retry_unsolved_random_point=5
bonmin.num_resolve_at_infeasibles=5
bonmin.algorithm=B-BB
bonmin.time_limit=45
acceptable_tol=0.001
max_cpu_time=20
max_iter=1000
bound_relax_factor=0.0
bonmin.random_generator_seed=2022706491
bonmin.num_resolve_at_root=10
bonmin.num_retry_unsolved_random_point=5
bonmin.num_resolve_at_infeasibles=5
bonmin.algorithm=B-BB
bonmin.time_limit=45
acceptable_tol=0.001
max_cpu_time=20
max_iter=1000
bound_relax_factor=0.0
bonmin.random_generator_seed=2022706491


******************************************************************************
This program contains Ipopt, a library for large-scale nonlinear optimization.
 Ipopt is released as open source code under the Eclipse Public License (EPL).
         For more information visit http://projects.coin-or.org/Ipopt
******************************************************************************

NLP0012I
              Num      Status      Obj             It       time                 Location
NLP0014I             1         OPT 1.5368658e-08       22 0.02
NLP0014I             1         OPT 6.081148e-08       20 0.039         resolve cost
NLP0014I             2         OPT 1.5423673e-06       22 0.026         resolve cost
NLP0014I *           3         OPT 1.1875717e-08       18 0.013         resolve cost
NLP0014I             4         OPT 3.5712183e-07       21 0.016         resolve cost
NLP0014I             5         OPT 2.0506616e-07       20 0.015         resolve cost
NLP0014I             6         OPT 3.8389438e-08       21 0.017         resolve cost
NLP0014I             7         OPT 3.369314e-07       22 0.018         resolve cost
NLP0014I             8         OPT 1.922678e-08       31 0.023         resolve cost
NLP0014I             9         OPT 1.1123551e-06       22 0.017         resolve cost
NLP0014I            10         OPT 3.262109e-08       32 0.023         resolve cost
NLP0014I            12         OPT 3.2833599e-08       16 0.01
NLP0014I            13         OPT 4.4788435e-08       16 0.009
NLP0014I            14         OPT 2.2190148e-08       16 0.01
NLP0014I            15         OPT 1.4094962e-08       18 0.011
NLP0014I            16         OPT 1.224909e-08        6 0.004
NLP0014I            17         OPT 2.9636697e-08       15 0.011
NLP0014I            18         OPT 3.4939199e-08       16 0.01
NLP0014I            19         OPT 4.0671188e-08       16 0.01
NLP0014I            20         OPT 2.1772824e-08       17 0.01
NLP0012I
              Num      Status      Obj             It       time                 Location
NLP0014I            21         OPT 2.1052713e-08       17 0.01
NLP0014I            22         OPT 6.8663936e-10        7 0.004
NLP0014I            23         OPT 2.0394073e-08       17 0.01
NLP0014I            24         OPT 1.2708758e-08       18 0.011
NLP0014I            25         OPT 1.4927417e-08        6 0.004
NLP0014I            26         OPT 2.6861912e-08       16 0.01
NLP0014I            27         OPT 5.1282074e-08       16 0.011
NLP0014I            28         OPT 2.4586885e-08       17 0.01
NLP0014I            29         OPT 2.3758132e-08       16 0.009
NLP0014I            30         OPT 1.5781035e-08       18 0.01
NLP0014I            31         OPT 3.6638562e-08       15 0.009
NLP0014I            32         OPT 1.5220174e-08       17 0.011
NLP0014I            33         OPT 4.2723365e-09        7 0.005
NLP0014I            34         OPT 2.9037725e-08       16 0.01
NLP0014I            35         OPT 3.2040345e-08       16 0.009
NLP0014I            36         OPT 3.9631916e-09        6 0.005
NLP0014I            37         OPT 1.5786855e-08       18 0.012
NLP0014I            38         OPT 1.5306431e-08       17 0.011
NLP0014I            39         OPT 4.2691747e-09        7 0.005
Cbc0010I After 0 nodes, 1 on tree, 1e+50 best solution, best possible -1.7976931e+308 (0.26 seconds)
NLP0014I            40         OPT 3.4939199e-08       16 0.01
NLP0012I
              Num      Status      Obj             It       time                 Location
NLP0014I            41         OPT 4.0671188e-08       16 0.009
NLP0014I            42         OPT 2.9189601e-08       16 0.009
NLP0014I            43         OPT 1.3809928e-08       18 0.01
NLP0014I            44         OPT 1.267695e-08       18 0.01
NLP0014I            45         OPT 1.6031773e-08       18 0.011
NLP0014I            46         OPT 2.2735624e-08       17 0.01
NLP0014I            47         OPT 1.3747335e-08       18 0.011
NLP0014I            48         OPT 1.4755186e-08       18 0.011
NLP0014I            49         OPT 3.1297588e-08       17 0.009
NLP0014I            50         OPT 1.5375259e-08       18 0.01
NLP0014I            51         OPT 1.5099603e-08       18 0.011
NLP0014I            52         OPT 1.5655114e-08       18 0.011
NLP0014I            53         OPT 1.5305098e-08       18 0.01
NLP0014I            54         OPT 1.5398022e-08       18 0.01
NLP0014I            55         OPT 2.4405407e-08       18 0.011
NLP0014I            56         OPT 1.2876714e-08       19 0.011
NLP0014I            57         OPT 1.4102077e-08       19 0.011
NLP0014I            58         OPT 2.8227499e-08       18 0.011
NLP0014I            59         OPT 1.4445821e-08       19 0.011
NLP0014I            60         OPT 1.4638933e-08       19 0.011
NLP0012I
              Num      Status      Obj             It       time                 Location
NLP0014I            61         OPT 3.562131e-08       18 0.011
NLP0014I            62         OPT 1.5185757e-08       19 0.012
NLP0014I            63         OPT 3.3765444e-08       19 0.011
NLP0014I            64         OPT 1.8093843e-08       19 0.012
NLP0014I            65         OPT 1.867984e-08       19 0.012
NLP0014I            66         OPT 2.0721794e-08       19 0.012
NLP0014I            67         OPT 2.1117049e-08       18 0.011
NLP0014I            68         OPT 2.2396109e-08       19 0.012
NLP0014I            69         OPT 1.8240002e-08       19 0.011
NLP0014I            70         OPT 3.5196256e-08       18 0.011
NLP0014I            71         OPT 1.8231071e-08       19 0.011
NLP0014I            72         OPT 3.1672002e-08       20 0.012
NLP0014I            73         OPT 1.8634078e-08       19 0.011
NLP0014I            74         OPT 2.5778279e-08       19 0.011
NLP0014I            75         OPT 4.3905933e-08       20 0.012
NLP0014I            76         OPT 2.0780938e-08       19 0.011
NLP0014I            77         OPT 1.1614821e-07       20 0.011
NLP0014I            78         OPT 4.7960196e-08       20 0.012
NLP0014I            79         OPT 4.9738941e-08       20 0.012
NLP0014I            80         OPT 8.0046558e-08       20 0.011
NLP0012I
              Num      Status      Obj             It       time                 Location
NLP0014I            81         OPT 9.8852822e-08       20 0.011
NLP0014I            82         OPT 3.3684484e-07        8 0.005
NLP0014I            83         OPT 3.7907738e-07        8 0.004
NLP0014I            84         OPT 6.8104142e-07        8 0.005
NLP0014I            85         OPT 1.0686623e-07        9 0.006
NLP0014I            86         OPT 8.8470666e-08       15 0.009
NLP0014I            87         OPT 1.0266982e-07        8 0.005
NLP0014I            88         OPT 7.4475486e-08        8 0.005
NLP0014I            89         OPT 5.4911988e-08       10 0.006
NLP0014I            90         OPT 6.2409542e-08       17 0.011
NLP0014I            91         OPT 7.2089469e-08        8 0.005
NLP0014I            92         OPT 4.7845899e-08       10 0.006
NLP0014I            93         OPT 5.4996465e-08       18 0.012
NLP0014I            94         OPT 6.711142e-08       11 0.007
NLP0014I            95         OPT 4.7421553e-08       10 0.006
NLP0014I            96         OPT 5.3362863e-08        8 0.004
NLP0014I            97         OPT 3.6152544e-08       12 0.007
NLP0014I            98         OPT 3.5731936e-08       13 0.009
NLP0014I            99         OPT 3.7791943e-08       13 0.009
NLP0014I           100         OPT 4.6253615e-08        9 0.006
NLP0012I
              Num      Status      Obj             It       time                 Location
NLP0014I           101         OPT 5.9661201e-08        8 0.005
NLP0014I           102         OPT 4.9494016e-08       10 0.007
NLP0014I           103         OPT 5.6662291e-08        8 0.005
NLP0014I           104         OPT 6.0434176e-08        8 0.005
NLP0014I           105         OPT 6.0223858e-08        8 0.005
NLP0014I           106         OPT 4.6588684e-08        9 0.006
NLP0014I           107         OPT 4.6328656e-08       10 0.006
NLP0014I           108         OPT 7.3874589e-08        9 0.006
NLP0014I           109         OPT 5.1481367e-08        9 0.006
NLP0014I           110         OPT 3.6225768e-08       11 0.006
NLP0014I           111         OPT 5.3499446e-08        9 0.005
NLP0014I           112         OPT 4.5089385e-08       10 0.006
NLP0014I           113         OPT 4.9446981e-08        8 0.005
NLP0014I           114         OPT 3.9445649e-08        8 0.005
NLP0014I           115         OPT 3.972964e-08        8 0.005
NLP0014I           116         OPT 1.3171484e-07        7 0.005
NLP0014I           117         OPT 5.1065865e-08       10 0.006
NLP0014I           118         OPT 1.3491277e-07        7 0.005
NLP0014I           119         OPT 1.3459142e-07        7 0.005
NLP0014I           120         OPT 1.3097052e-07        7 0.004
NLP0012I
              Num      Status      Obj             It       time                 Location
NLP0014I           121         OPT 1.2679096e-07        7 0.004
NLP0014I           122         OPT 1.3762977e-07        7 0.005
NLP0014I           123         OPT 1.2662357e-07        4 0.002
NLP0012I
              Num      Status      Obj             It       time                 Location
NLP0014I             1         OPT 1.2662357e-07        3 0.002
Cbc0004I Integer solution of 1.2662357e-07 found after 1169 iterations and 84 nodes (1.00 seconds)
Cbc0001I Search completed - best objective 1.266235713833962e-07, took 1169 iterations and 84 nodes (1.00 seconds)
Cbc0032I Strong branching done 14 times (403 iterations), fathomed 0 nodes and fixed 0 variables
Cbc0035I Maximum depth 42, 0 variables fixed on reduced cost

        "Finished"

However, I eventually randomly get the error raise RuntimeError('Solver ' + 'bonmin' + 'not found') with no solver output at all.

If it helps, I am solving a problem where all the decision variables are integers, and my version of rbfopt is 4.2.4.

[Florent-H]

Small update:

I get the same error after several iterations, even when all the decision variables are reals (i.e., no integers).

[gnannicini]

The error does not make much sense (all solvers are called in exactly the same way throughout the algorithm, so I don't see why bonmin would 'disappear' after some iterations); I wonder if it's something related to the filesystem or some strange interaction with Pyomo.

At the very least, please post the output that you get with debug=True, print_solver_output=True.

Even better, please post a way to reproduce the bug: I doubt I can do much without reproducing.

You should create your own issue because this is not related to the initial issue.

[Florent-H]

I found a solution to my problem but not the root cause. I had previously modified the source code of rbfopt by replacing the multiprocessing.Pool class by the concurrent.futures.ProcessPoolExecutor class. This switch allowed me to have a parallelized objective function as nested pools are allowed with the concurrent package but not the multiprocessing package.

Although this package switch never caused any issues with paths in the past, it appears that for this particular optimization problem, making the objective function sequential removed the solver bonmin not found error.

[gnannicini]

Since the error did not occur with an official RBFOpt release, I'm going to close this one.