AMPL cannot find "minos"

Question

I've faced a problem with AMPL. I'm using 32-bit version of Linux OS. I'm trying to solve a simple linear programmin problem but I can't understand what is wrong... Here is model, data files and session script as well. The answer to command "solve" is: Cannot find "minos". But the solver is currently in my folder! Changing the solvers doesn't help. Any suggestions?

Model of the problem:

param n;
param t;
param p{i in 1..n};
param r{i in 1..n};
param m{i in 1..n};
#Declaration of variables
var x {i in 1..n} >=0;
#Objective Function
maximize revenues: sum {i in 1..n} p[i]*x[i] ;
#Constraints
subject to Aval_Time: sum{i in 1..n} x[i]/r[i]<=t;
subject to Max_Flavor {i in 1..n}: x[i]<=m[i];

Data of the problem:

param n := 4;# No of Flavors
param t := 40; # Total labor hour in a week
param p := 1 1 2 1.5 3 1 4 1.5; # Revenue per package flavor i
param r := 1 40 2 30 3 50 4 20; # Production rate of package flavor i
param m := 1 1000 2 900 3 500 4 800; # Maximum demand package flavor i

AMPL session:

reset;
model example2.mod;
data example2.dat;
solve;
display x;

Answer of the system:

Cannot find "minos"

score 5 · Accepted Answer · answered Mar 16 '13 at 19:10

5

The error message is trying to tell you that the solver is missing. AMPL doesn't solve your problem, it just transforms your model into a form suitable for the solver, passes that to the solver and the actual solution is done by the solver. That is about the error message.

You need a solver to resolve this issue. Download and the extract the minos solver. Make it exectuable: In the Bash shell (not the AMPL shell) issue the following:

chmod +x minos

You also have tell AMPL where the solver is before you issue the solve; command. Before the solve command, issue this either in the AMPL shell or in your model file:

option solver "/path/to/minos";

where you change /path/to/minos according to your installation.

That's all.

answered Mar 16 '13 at 19:10

Ali

56,466
29
168
265

Hmm... Actualy I know that AMPL doesn't solve the problem directly. The minos solver have been already downloaded and extracted. The executable flag (chmod +x) is true. Moreover this binary file is located in the same derictory where my AMPL located. But it still doesn't work and the AMPL shows me that error message (cannot find "minos")... – Roman Dryndik Mar 16 '13 at 21:16
@RomanDryndik Did you try the `option solver "/path/to/minos";` I suggested in my answer? – Ali Mar 16 '13 at 23:17
@RomanDryndik Yes, that is one way of doing it, that assumes that the minos solver is in the same folder as the ampl executable. Please consider accepting an answer. – Ali Apr 14 '13 at 12:27

score 5 · Answer 2 · answered Mar 17 '13 at 15:24

On Unix and Unix-like operating systems such as Linux, the current directory is usually not on the search path. You have the following options:

Use option solver './minos'; before the solve command.
Similar to above but use the absolute path to minos as suggested by Ali.
Add the path to AMPL directory to the PATH environment variable.
Copy (or create a symbolic link) minos to some directory on the search path such as /usr/local/bin

Roman Dryndik · Answer 3 · 2023-01-25T09:25:35.463

2

The problem was resolved by executing option solver "./minos"; in a folder with AMPL.

edited Jan 25 '23 at 09:25

answered Apr 14 '13 at 12:20

Roman Dryndik

1,167
1
13
34

AMPL cannot find "minos"

3 Answers3