callback_c.c
/* Copyright 2009, Gurobi Optimization, Inc. */
/* This example reads an LP or a MIP from a file, sets a callback
to monitor the optimization progress and to output some progress
information to the screen and to a log file. If it is a MIP and 10%
gap is reached, then it aborts */
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include "gurobi_c.h"
/* Define structure to pass my data to the callback function */
struct callback_data {
double lastmsg;
FILE *logfile;
double *solution;
};
int __stdcall
mycallback(GRBmodel *model,
void *cbdata,
int where,
void *usrdata)
{
struct callback_data *mydata = (struct callback_data *) usrdata;
char *msg;
if (where == GRB_CB_POLLING) {
/* Ignore polling callback */
} else if (where == GRB_CB_MESSAGE) {
GRBcbget(cbdata, where, GRB_CB_MSG_STRING, &msg);
fprintf(mydata->logfile, "%s", msg);
} else if (where == GRB_CB_SIMPLEX) {
double pinf, dinf, obj, itrcnt;
int ispert;
char ch;
GRBcbget(cbdata, where, GRB_CB_SPX_ITRCNT, &itrcnt);
if (((int) itrcnt)%100 == 1) {
GRBcbget(cbdata, where, GRB_CB_SPX_ISPERT, &ispert);
GRBcbget(cbdata, where, GRB_CB_SPX_OBJVAL, &obj);
GRBcbget(cbdata, where, GRB_CB_SPX_PRIMINF, &pinf);
GRBcbget(cbdata, where, GRB_CB_SPX_DUALINF, &dinf);
if (ispert == 0) ch = ' ';
else if (ispert == 1) ch = 'S';
else ch = 'P';
printf("%7.0f %14.7e%c %13.6e %13.6e\n", itrcnt, obj, ch, pinf, dinf);
}
} else if (where == GRB_CB_PRESOLVE) {
int cdels, rdels;
GRBcbget(cbdata, where, GRB_CB_PRE_COLDEL, &cdels);
GRBcbget(cbdata, where, GRB_CB_PRE_ROWDEL, &rdels);
if (cdels || rdels) {
printf("%7d columns and %7d rows are removed\n", cdels, rdels);
}
} else if (where == GRB_CB_MIP) {
double objbst, objbnd, nodecnt, actnodes, itrcnt;
int cutcnt, solcnt;
GRBcbget(cbdata, where, GRB_CB_MIP_NODCNT, &nodecnt);
if (nodecnt - mydata->lastmsg >= 100) {
mydata->lastmsg = nodecnt;
GRBcbget(cbdata, where, GRB_CB_MIP_OBJBST, &objbst);
GRBcbget(cbdata, where, GRB_CB_MIP_OBJBND, &objbnd);
/* if gap is small, then quit */
if (fabs(objbst - objbnd) < 0.1 * (1.0 + fabs(objbst)))
GRBterminate(model);
GRBcbget(cbdata, where, GRB_CB_MIP_NODLFT, &actnodes);
GRBcbget(cbdata, where, GRB_CB_MIP_ITRCNT, &itrcnt);
GRBcbget(cbdata, where, GRB_CB_MIP_SOLCNT, &solcnt);
GRBcbget(cbdata, where, GRB_CB_MIP_CUTCNT, &cutcnt);
printf("%7.0f %7.0f %8.0f %13.6e %13.6e %7d %7d\n",
nodecnt, actnodes, itrcnt, objbst, objbnd, solcnt, cutcnt);
}
} else if (where == GRB_CB_MIPSOL) {
double obj, nodecnt;
int solcnt;
GRBcbget(cbdata, where, GRB_CB_MIPSOL_OBJ, &obj);
GRBcbget(cbdata, where, GRB_CB_MIPSOL_NODCNT, &nodecnt);
GRBcbget(cbdata, where, GRB_CB_MIPSOL_SOLCNT, &solcnt);
GRBcbget(cbdata, where, GRB_CB_MIPSOL_SOL, mydata->solution);
printf("**** New solution at node %.0f, obj %g, sol %d, x[0] = %.2f ****\n",
nodecnt, obj, solcnt, mydata->solution[0]);
}
return 0;
}
int
main(int argc,
char *argv[])
{
GRBenv *env = NULL;
GRBmodel *model = NULL;
int error = 0;
int vars, optimstatus;
double objval;
struct callback_data mydata;
mydata.lastmsg = -GRB_INFINITY;
mydata.logfile = NULL;
mydata.solution = NULL;
if (argc < 2) {
fprintf(stderr, "Usage: callback_c filename\n");
goto QUIT;
}
mydata.logfile = fopen("cb.log", "w");
if (!mydata.logfile) {
fprintf(stderr, "Cannot open cb.log for callback message\n");
goto QUIT;
}
/* Create environment */
error = GRBloadenv(&env, NULL);
if (error || env == NULL) {
fprintf(stderr, "Error: could not create environment\n");
exit(1);
}
/* Turn off display */
error = GRBsetintparam(env, GRB_INT_PAR_OUTPUTFLAG, 0);
if (error) goto QUIT;
/* Read model from file */
error = GRBreadmodel(env, argv[1], &model);
if (error) goto QUIT;
/* Allocate space for solution */
error = GRBgetintattr(model, GRB_INT_ATTR_NUMVARS, &vars);
if (error) goto QUIT;
mydata.solution = malloc(vars*sizeof(double));
if (mydata.solution == NULL) {
fprintf(stderr, "Failed to allocate memory\n");
exit(1);
}
/* Set callback function */
error = GRBsetcallbackfunc(model, mycallback, (void *) &mydata);
if (error) goto QUIT;
/* Solve model */
error = GRBoptimize(model);
if (error) goto QUIT;
/* Capture solution information */
error = GRBgetintattr(model, GRB_INT_ATTR_STATUS, &optimstatus);
if (error) goto QUIT;
error = GRBgetdblattr(model, GRB_DBL_ATTR_OBJVAL, &objval);
if (error) goto QUIT;
printf("\nOptimization complete\n");
if (optimstatus == GRB_OPTIMAL)
printf("Optimal objective: %.4e\n", objval);
else if (optimstatus == GRB_INF_OR_UNBD)
printf("Model is infeasible or unbounded\n");
else
printf("Optimization was stopped early\n");
printf("\n");
QUIT:
/* Error reporting */
if (error) {
printf("ERROR: %s\n", GRBgeterrormsg(env));
exit(1);
}
/* Close file */
if (mydata.logfile)
fclose(mydata.logfile);
/* Free solution */
if (mydata.solution)
free(mydata.solution);
/* Free model */
GRBfreemodel(model);
/* Free environment */
GRBfreeenv(env);
return 0;
}