apis/examples_python/transport10_8py_source.html

from xlrd import open_workbook

from gams import *

import sys


def get_model_text():

    return '''

  Sets

       i   canning plants

       j   markets


  Parameters

       a(i)   capacity of plant i in cases

       b(j)   demand at market j in cases

       d(i,j) distance in thousands of miles

  Scalar f  freight in dollars per case per thousand miles /90/;


$if not set gdxincname $abort 'no include file name for data file provided'

$gdxin %gdxincname%

$load i j a b d

$gdxin


  Parameter c(i,j)  transport cost in thousands of dollars per case ;


            c(i,j) = f * d(i,j) / 1000 ;


  Variables

       x(i,j)  shipment quantities in cases

       z       total transportation costs in thousands of dollars ;


  Positive Variable x ;


  Equations

       cost        define objective function

       supply(i)   observe supply limit at plant i

       demand(j)   satisfy demand at market j ;


  cost ..        z  =e=  sum((i,j), c(i,j)*x(i,j)) ;


  supply(i) ..   sum(j, x(i,j))  =l=  a(i) ;


  demand(j) ..   sum(i, x(i,j))  =g=  b(j) ;


  Model transport /all/ ;


  Solve transport using lp minimizing z ;


  Display x.l, x.m ; '''


if __name__ == "__main__":

    wb = open_workbook("..\\Data\\transport.xlsx")


    capacity = wb.sheet_by_name("capacity")

    demand = wb.sheet_by_name("demand")

    distance = wb.sheet_by_name("distance")


    # number of markets/plants have to be the same in all spreadsheets

    assert (distance.ncols-1 == demand.ncols) and (distance.nrows-1 == capacity.ncols), \

            "Size of the spreadsheets doesn't match"


    if len(sys.argv) > 1:

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

    else:

        ws = GamsWorkspace()


    db = ws.add_database()

    i = db.add_set("i", 1, "Plants")

    j = db.add_set("j", 1, "Markets")

    capacity_param = db.add_parameter_dc("a", [i], "Capacity")

    demand_param = db.add_parameter_dc("b", [j], "Demand")

    distance_param = db.add_parameter_dc("d", [i,j], "Distance")


    for cx in range(capacity.ncols):

        i.add_record(str(capacity.cell_value(0, cx)))

        capacity_param.add_record(str(capacity.cell_value(0, cx))).value = capacity.cell_value(1, cx)


    for cx in range(demand.ncols):

        j.add_record(str(demand.cell_value(0, cx)))

        demand_param.add_record(str(demand.cell_value(0, cx))).value = demand.cell_value(1, cx)


    for cx in range(1, distance.ncols):

        for rx in range(1, distance.nrows):

            keys = ( str(distance.cell_value(rx, 0)), str(distance.cell_value(0, cx)) )

            distance_param.add_record(keys).value = distance.cell_value(rx, cx)


    # Create and run the GAMSJob

    t10 = ws.add_job_from_string(get_model_text())

    opt = ws.add_options()

    opt.defines["gdxincname"] = db.name

    opt.all_model_types = "xpress"

    t10.run(opt, databases=db)

    for rec in t10.out_db["x"]:

        print("x(" + rec.key(0) + "," + rec.key(1) + "): level=" + str(rec.level) + " marginal=" + str(rec.marginal))