Ampl

Introduction

In this example, we will explore how to submit an AMPL program to Multivac to compute a simple objective function.

Example Code

Suppose we want to minimize the following objective function:

\[f(x) = x^2 + 3x + 2\]

We will create a file named test_ampl.mod to compute the objective function value for a specific value of x:

# minimitzacio.mod
# Define the decision variable
var x;
# Define the objective function
minimize obj: x^2 + 3*x + 2;
# Define the constraint: x must be equal to 5
s.t. restriccio_x: x = 5;
# Solve the problem
solve;
# Show results
display x;
display obj;

This code defines the objective function, assigns a specific value to x (in this case, 5), and computes the objective function result for that value.

We will create a .dat file, for example test_ampl.dat, containing the input variables:

# minimitzacio.dat
# No input data is required for this example

Execution

We will create a configuration file, for example test_ampl.slurm, containing the execution settings for this AMPL script.

VERSION=1.3
JOB_NAME=ampl_example
NAME_OUTPUT=out
PARTITION=all
N_TASKS=1
CPUS_PER_TASK=1
MAIL_TYPE=END,FAIL
MAIL_USER=nom.usuari@upc.edu
MEMORY=1G
BEGIN=now
TIME_LIMIT=00:05:00
LOG_OUTPUT=log
FORCED_NODES=
EXCLUDED_NODES=
ROUTE=~/
COMMANDS=(
   "hostname" # To know which machine executed the job
   "/opt/ampl.linux-intel64/ampl test_ampl.mod test_ampl.dat"
)

We will submit this script from ``iocex`` using the following command:

multivac test_ampl.slurm

Once execution is complete, the output of our program will be visible in the same directory where the job was launched.