apis/examples_python/clad_8py_source.html

from gams import *

import sys

import os

from threading import Thread

try:

    from StringIO import StringIO

except ImportError:

    from io import StringIO


if __name__ == "__main__":

    if len(sys.argv) > 1:

        ws = GamsWorkspace(system_directory = sys.argv[1])

    else:

        ws = GamsWorkspace()


    # Use the GAMS Model Library model "clad" as an example


    ws.gamslib("clad")

    j1 = ws.add_job_from_file("clad")


    # Define an option file for the solver to be used

    f = open(os.path.join(ws.working_directory, "cplex.opt"), "w")

    # Set relative stopping tolerance to 0 initially

    f.write("epgap 0\n")

    # Activate interactive option setting on interrupt

    f.write("interactive 1\n")

    # Define new option file to read on interrupt

    f.write("iafile cplex.op2\n")

    f.close()


    opt = ws.add_options()

    opt.mip = "cplex"

    opt.optfile = 1

    opt.solvelink = SolveLink.LoadLibrary


    sw = StringIO()


    # Run GamsJob j1 in separate thread

    opt_thread = Thread(target=j1.run, args=(opt,), kwargs={"output":sw})

    opt_thread.start()


    # Define list of increasing stopping tolerances

    steps = [(5.0, "epgap 0.1"),

             (10.0, "epgap 0.2"),

             (20.0, "epagap 1e9")]


    prev_step = 0.0

    for s in steps:

        # Wait a while and check if j1 is still running

        opt_thread.join(s[0] - prev_step)

        if not opt_thread.is_alive():

            break

        prev_step = s[0]

        # Write new Cplex option file

        f = open(os.path.join(ws.working_directory, "cplex.op2"), "w")

        f.write(s[1])

        f.close()

        # Interrupt j1 to read new Cplex option file

        j1.interrupt()

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

    # If j1 is still running, wait until it is finished

    if opt_thread.is_alive:

        opt_thread.join()

    # Check if everything worked as expected

    log = sw.getvalue()

    if not "Interrupted..." in log:

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