apis/examples_python/clad_8py_source.html

from io import StringIO

import os

import sys

from threading import Thread

from gams import GamsWorkspace, SolveLink


if __name__ == "__main__":

    sys_dir = sys.argv[1] if len(sys.argv) > 1 else None

    ws = GamsWorkspace(system_directory=sys_dir)


    # use model "clad" from the GAMS Model Library

    ws.gamslib("clad")

    job = ws.add_job_from_file("clad")


    # define an option file for the solver to be used

    with open(os.path.join(ws.working_directory, "cplex.opt"), "w") as f:

        f.write("epgap 0\n")  # set relative stopping tolerance to 0 initially

        f.write("interactive 1\n")  # activate interactive option setting on interrupt

        f.write("iafile cplex.op2\n")  # define new option file to read on interrupt


    opt = ws.add_options()

    opt.mip = "cplex"

    opt.optfile = 1

    opt.solvelink = SolveLink.LoadLibrary

    opt.threads = 1


    # run GamsJob in separate thread

    sw = StringIO()

    thread = Thread(target=job.run, args=(opt,), kwargs={"output": sw})

    thread.start()


    # define list of increasing stopping tolerances

    steps = [(5.0, "epgap 0.1"), (10.0, "epgap 0.2"), (20.0, "epagap 1e9")]


    total_time = 0.0

    for s in steps:

        # wait a while and check if job is still running

        thread.join(s[0] - total_time)

        if not thread.is_alive():

            break

        total_time = s[0]

        # write new Cplex option file

        with open(os.path.join(ws.working_directory, "cplex.op2"), "w") as f:

            f.write(s[1])

        # interrupt job to read new Cplex option file

        job.interrupt()

        print("Interrupted Cplex to continue with new option: " + s[1])


    # if job is still running, wait until it is finished

    if thread.is_alive():

        thread.join()

    # check if we did interrupt the solver at least once

    log = sw.getvalue()

    if not "Interrupted..." in log:

        raise Exception("Expected the solver to be interrupted at least once.")