/*------------------------------------------------------------------------*/
/* File: examples/src/netex1.c */
/* Version 8.1 */
/*------------------------------------------------------------------------*/
/* Copyright (C) 1997-2002 by ILOG. */
/* All Rights Reserved. */
/* Permission is expressly granted to use this example in the */
/* course of developing applications that use ILOG products. */
/*------------------------------------------------------------------------*/
/* netex1.c - Entering and optimizing a network problem */
/* Import the CPLEX function declarations and the C library
header file stdio.h with the include of cplex.h. */
#include <ilcplex/cplex.h>
#include <stdlib.h>
/* Import the declarations for the string functions */
#include <string.h>
/* Forward declaration for function at end of program */
static int
buildNetwork (CPXENVptr env, CPXNETptr net);
static void
free_and_null (char **ptr);
int
main (void)
{
/* Declare variables and arrays for retrieving problem data and
solution information later on. */
int narcs;
int nnodes;
int solstat;
double objval;
double *x = NULL;
double *pi = NULL;
double *slack = NULL;
double *dj = NULL;
CPXENVptr env = NULL;
CPXNETptr net = NULL;
int status;
int i, j;
/* Initialize the CPLEX environment */
env = CPXopenCPLEX (&status);
/* If an error occurs, the status value indicates the reason for
failure. A call to CPXgeterrorstring will produce the text of
the error message. Note that CPXopenCPLEX produces no
output, so the only way to see the cause of the error is to use
CPXgeterrorstring. For other CPLEX routines, the errors will
be seen if the CPX_PARAM_SCRIND indicator is set to CPX_ON. */
if ( env == NULL ) {
char errmsg[1024];
fprintf (stderr, "Could not open CPLEX environment.\n");
CPXgeterrorstring (env, status, errmsg);
fprintf (stderr, "%s", errmsg);
goto TERMINATE;
}
/* Turn on output to the screen */
status = CPXsetintparam (env, CPX_PARAM_SCRIND, CPX_ON);
if ( status ) {
fprintf (stderr,
"Failure to turn on screen indicator, error %d.\n", status);
goto TERMINATE;
}
/* Create the problem. */
net = CPXNETcreateprob (env, &status, "netex1");
/* A returned pointer of NULL may mean that not enough memory
was available or there was some other problem. In the case of
failure, an error message will have been written to the error
channel from inside CPLEX. In this example, the setting of
the parameter CPX_PARAM_SCRIND causes the error message to
appear on stdout. */
if ( net == NULL ) {
fprintf (stderr, "Failed to create network object.\n");
goto TERMINATE;
}
/* Fill in the data for the problem. Note that since the space for
the data already exists in local variables, we pass the arrays
directly to the routine to fill in the data structures. */
status = buildNetwork (env, net);
if ( status ) {
fprintf (stderr, "Failed to build network problem.\n");
goto TERMINATE;
}
/* Optimize the problem and obtain solution. */
status = CPXNETprimopt (env, net);
if ( status ) {
fprintf (stderr, "Failed to optimize network.\n");
goto TERMINATE;
}
/* get network dimensions */
narcs = CPXNETgetnumarcs (env, net);
nnodes = CPXNETgetnumnodes (env, net);
/* allocate memory for solution data */
x = (double *) malloc (narcs * sizeof (double));
dj = (double *) malloc (narcs * sizeof (double));
pi = (double *) malloc (nnodes * sizeof (double));
slack = (double *) malloc (nnodes * sizeof (double));
if ( x == NULL ||
dj == NULL ||
pi == NULL ||
slack == NULL ) {
fprintf (stderr, "Failed to allocate arrays.\n");
goto TERMINATE;
}
status = CPXNETsolution (env, net, &solstat, &objval, x, pi, slack, dj);
if ( status ) {
fprintf (stderr, "Failed to obtain solution.\n");
goto TERMINATE;
}
/* Write the output to the screen. */
printf ("\nSolution status = %d\n", solstat);
printf ("Solution value = %f\n\n", objval);
for (i = 0; i < nnodes; i++) {
printf ("Node %2d: Slack = %10f Pi = %10f\n", i, slack[i], pi[i]);
}
for (j = 0; j < narcs; j++) {
printf ("Arc %2d: Value = %10f Reduced cost = %10f\n",
j, x[j], dj[j]);
}
/* Finally, write a copy of the problem to a file. */
status = CPXNETwriteprob (env, net, "netex1.net", NULL);
if ( status ) {
fprintf (stderr, "Failed to write network to disk.\n");
goto TERMINATE;
}
TERMINATE:
/* Free memory for solution data */
free_and_null ((char **) &x);
free_and_null ((char **) &dj);
free_and_null ((char **) &pi);
free_and_null ((char **) &slack);
/* Free up the problem as allocated by CPXNETcreateprob, if necessary */
if ( net != NULL ) {
CPXNETfreeprob (env, &net);
if ( status ) {
fprintf (stderr, "CPXNETfreeprob failed, error code %d.\n", status);
}
}
/* Free up the CPLEX environment, if necessary */
if ( env != NULL ) {
status = CPXcloseCPLEX (&env);
/* Note that CPXcloseCPLEX produces no output,
so the only way to see the cause of the error is to use
CPXgeterrorstring. For other CPLEX routines, the errors will
be seen if the CPX_PARAM_SCRIND indicator is set to CPX_ON. */
if ( status ) {
char errmsg[1024];
fprintf (stderr, "Could not close CPLEX environment.\n");
CPXgeterrorstring (env, status, errmsg);
fprintf (stderr, "%s", errmsg);
}
}
return (status);
} /* END main */
static int
buildNetwork (CPXENVptr env, CPXNETptr net)
{
int status = 0;
/* definitions to improve readability */
# define NNODES 8
# define NARCS 14
# define inf CPX_INFBOUND
/* Define list of supply values for the nodes */
double supply[NNODES] = {20.0, 0.0, 0.0, -15.0, 5.0, 0.0, 0.0, -10.0};
/* Define list of tail or from-node indices as well as head or
to-node indices for the arcs. Notice that according to C
standard the first node has index 0. */
int tail[NARCS] = { 0, 1, 2, 3, 6, 5, 4,
4, 2, 3, 3, 5, 5, 1};
int head[NARCS] = { 1, 2, 3, 6, 5, 7, 7,
1, 1, 4, 5, 3, 4, 5};
/* Define list of objective values and lower and upper bound values
for the arcs */
double obj [NARCS] = { 3.0, 3.0, 4.0, 3.0, 5.0, 6.0, 7.0,
4.0, 2.0, 6.0, 5.0, 4.0, 3.0, 6.0};
double ub [NARCS] = {24.0, 25.0, 12.0, 10.0, 9.0, inf, 20.0,
10.0, 5.0, 15.0, 10.0, 11.0, 6.0, inf};
double lb [NARCS] = {18.0, 0.0, 12.0, 0.0, 0.0, -inf, 0.0,
0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0};
/* Delete existing network. This is not necessary in this
context since we know we have an empty network object.
Notice that CPXNETdelnodes deletes all arcs incident to
the deleted nodes as well. Therefore this one function
call effectively deletes an existing network problem. */
if ( CPXNETgetnumnodes (env, net) > 0 ) {
status = CPXNETdelnodes (env, net, 0,
CPXNETgetnumnodes (env, net)-1);
if ( status ) goto TERMINATE;
}
/* Set growth rates for rows/nodes and columns/arcs. This
is to avoid internal memory reallocations while adding
nodes and arcs. Since we are adding all nodes and all
arcs using only one function call for each it is actually
unnecessary, but if more function calls are used, finding
the right settings may improve performance. */
status = CPXsetintparam (env, CPX_PARAM_ROWGROWTH, NNODES);
if ( status ) goto TERMINATE;
status = CPXsetintparam (env, CPX_PARAM_COLGROWTH, NARCS);
if ( status ) goto TERMINATE;
/* Set optimization sense */
status = CPXNETchgobjsen (env, net, CPX_MIN);
if ( status ) goto TERMINATE;
/* Add nodes to network along with their supply values,
but without any names. */
status = CPXNETaddnodes (env, net, NNODES, supply, NULL);
if ( status ) goto TERMINATE;
/* Add arcs to network along with their objective values and
bounds, but without any names. */
status = CPXNETaddarcs (env, net, NARCS, tail, head, lb, ub, obj, NULL);
if ( status ) goto TERMINATE;
TERMINATE:
return (status);
} /* END buildnetwork */
static void
free_and_null (char **ptr)
{
if ( *ptr != NULL ) {
free (*ptr);
*ptr = NULL;
}
} /* END free_and_null */
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