/***********************************************************************
Xpress Optimizer Examples
=========================
file repair.c
`````````````
Demonstrates the FICO repairinfeas utility.
Prints a relaxation summary and creates the relaxed subproblem.
(c) 2017-2025 Fair Isaac Corporation
***********************************************************************/
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <string.h>
#include "xprs.h"
/* Calls an Xpress optimizer function and checks the return code.
* If the call fails then the function
* - prints a short error message to stderr,
* - sets variable 'returnCode' to the error,
* - and branches to label 'cleanup'.
*/
#define CHECK_RETURN(call) do { \
int result_ = call; \
if ( result_ != 0 ) { \
fprintf(stderr, "Line %d: %s failed with %d\n", \
__LINE__, #call, result_); \
returnCode = result_; \
goto cleanup; \
} \
} while (0)
static void XPRS_CC messagecb(XPRSprob cbprob, void* cbdata,
const char *msg, int len, int msgtype);
static int Getinfeasibilitybreakers(XPRSprob prob, const double *x,
const double *slacks, double constraints[],
double bounds[], const double tolarence);
static int Generatefeasibilityreport(XPRSprob prob,
const double *constraintviolations,
const double *boundviolations);
static int Getrowbounds(XPRSprob prob, const int row, double *lb, double *ub);
static int Applyrepairinfeasresulttoproblem(XPRSprob prob,
const double *constraintviolations,
const double *boundviolations);
static int Setrowbounds(XPRSprob prob, const int i, const double lb, const
double ub);
int main(int argc, char **argv) {
int returnCode = 0;
XPRSprob prob = NULL; /* The problem instance */
int i, j;
int Status; /* Status of Optimizer subroutines */
char const *sProblem = "../data/iisexample"; /* Problem name */
int nrows, ncols;
double *x = NULL, *slacks = NULL;
double *constraintviolations = NULL, *boundviolations = NULL;
int ndiscretecols, nsets;
double *lrp_array = NULL; /* Array of size ROWS containing the preferences
for relaxing the less or equal side of row. */
double *grp_array = NULL; /* Array of size ROWS containing the preferences
for relaxing the greater or equal side of a row. */
double *lbp_array = NULL; /* Array of size COLS containing the preferences
for relaxing lower bounds. */
double *ubp_array = NULL; /* Array of size COLS containing preferences for
relaxing upper bounds. */
/* Parse the arguments to the program. */
if (argc != 1 && argc != 2) {
printf("syntax: repair [filename] \n");
return(1);
}
if (argc == 2)
sProblem = argv[1];
/* Initialize the optimizer. */
if ( XPRSinit("") != 0 ) {
char message[512];
XPRSgetlicerrmsg(message, sizeof(message));
fprintf(stderr, "Licensing error: %s\n", message);
return 1;
}
/* Create a new problem and immediately register a message handler.
* Once we have a message handler installed, errors will produce verbose
* error messages on the console and we can limit ourselves to minimal
* error handling in the code here.
*/
CHECK_RETURN( XPRScreateprob(&prob) );
CHECK_RETURN( XPRSaddcbmessage(prob, messagecb, NULL, 0) );
/* Load problem file */
CHECK_RETURN( XPRSreadprob(prob, sProblem, "") );
/* Get problem size */
CHECK_RETURN( XPRSgetintattrib(prob, XPRS_INPUTROWS, &nrows) );
CHECK_RETURN( XPRSgetintattrib(prob, XPRS_INPUTCOLS, &ncols) );
/* Allocate memory for the preference arrays, the solution and the
* infeasibility breakers
*/
lrp_array = malloc(nrows*sizeof(*lrp_array));
grp_array = malloc(nrows*sizeof(*grp_array));
lbp_array = malloc(ncols*sizeof(*lbp_array));
ubp_array = malloc(ncols*sizeof(*ubp_array));
x = malloc(ncols*sizeof(*x));
slacks = malloc(nrows*sizeof(*slacks));
boundviolations = malloc(ncols*sizeof(*boundviolations));
constraintviolations = malloc(nrows*sizeof(*constraintviolations));
if (!lrp_array || !grp_array || !lbp_array || !ubp_array ||
!x || !slacks || !boundviolations || !constraintviolations )
{
perror("malloc");
returnCode = -2;
goto cleanup;
}
/* Set relaxation values */
for (i=0; i<nrows; i++) {
lrp_array[i] = 1;
grp_array[i] = 1;
}
for (j=0; j<ncols; j++) {
lbp_array[j] = 1;
ubp_array[j] = 1;
}
/* Call repairinfeas */
Status = -1; /* set a dummy value */
CHECK_RETURN( XPRSrepairweightedinfeas(prob, &Status, lrp_array, grp_array,
lbp_array, ubp_array, 'n', 0.001, "") );
printf("Repairinfeas return code (%i): ", Status);
switch(Status) {
case 0: printf("relaxed optimum found\n"); break;
case 1: printf("relaxed problem is infeasible\n"); break;
case 2: printf("relaxed problem is unbounded\n"); break;
case 3: printf("solution of the relaxed problem regarding the original objective is nonoptimal\n"); break;
case 4: printf("error\n"); break;
case 5: printf("numerical instability\n"); break;
}
XPRSgetmipentities(prob, &ndiscretecols, &nsets, NULL, NULL, NULL, NULL, NULL, NULL,
NULL);
/* Get solution */
XPRSgetsolution(prob, NULL, x, 0, ncols - 1);
XPRSgetslacks(prob, NULL, x, 0, nrows - 1);
/* Get the values of the breaker variables */
CHECK_RETURN( Getinfeasibilitybreakers(prob, x, slacks, constraintviolations,
boundviolations, 1.0e-6) );
/* Print report */
CHECK_RETURN( Generatefeasibilityreport(prob, constraintviolations,
boundviolations) );
/* Repair and save problem */
CHECK_RETURN( Applyrepairinfeasresulttoproblem(prob, constraintviolations,
boundviolations) );
CHECK_RETURN( XPRSwriteprob(prob, "repaired.lp","lp") );
printf("Repaired problem is written as repaired.lp.\n");
printf("(Please note that this matrix might show slightly different behaviour then the repairinfeas problem)\n\n");
cleanup:
if (returnCode > 0) {
/* There was an error with the solver. Get the error code and error message.
* If prob is still NULL then the error was in XPRScreateprob() and
* we cannot find more detailed error information.
*/
if (prob != NULL) {
int errorCode = -1;
char errorMessage[512] = {0};
XPRSgetintattrib(prob, XPRS_ERRORCODE, &errorCode);
XPRSgetlasterror(prob, errorMessage);
fprintf(stderr, "Error %d: %s\n", errorCode, errorMessage);
}
}
/* Free the resources (variables are initialized so that this is valid
* even in case of error).
*/
free(lrp_array);
free(grp_array);
free(lbp_array);
free(ubp_array);
free(x);
free(slacks);
free(boundviolations);
free(constraintviolations);
/* Destroy problem object and free environment */
XPRSdestroyprob(prob);
XPRSfree();
return returnCode;
}
/*
This function returns the lower and upper bounds for a row.
*/
int Getrowbounds(XPRSprob prob, const int i, double *lb, double *ub) {
int returnCode = 0;
char rowtype;
double rhs, range;
/* the bounds are calculated using the rhs, the range and the type of the row
*/
CHECK_RETURN( XPRSgetrhs(prob, &rhs, i, i) );
CHECK_RETURN( XPRSgetrhsrange(prob, &range, i, i) );
CHECK_RETURN( XPRSgetrowtype(prob, &rowtype, i, i) );
switch (rowtype) {
case 'L': {
*lb = XPRS_MINUSINFINITY;
*ub = rhs;
} break;
case 'E': {
*lb = rhs;
*ub = rhs;
} break;
case 'G': {
*lb = rhs;
*ub = XPRS_PLUSINFINITY;
} break;
case 'R': {
*lb = rhs-range;
*ub = rhs;
} break;
default: {
*lb = XPRS_MINUSINFINITY;
*ub = XPRS_PLUSINFINITY;
}
}
cleanup:
return returnCode;
}
/*
This function sets new lower and upper bounds for a row.
*/
int Setrowbounds(XPRSprob prob, const int i, const double dlb, const double
dub) {
int returnCode = 0;
char rowtype;
double lb, ub, range;
if (dlb < dub) {
lb = dlb;
ub = dub;
} else {
lb = dub;
ub = dlb;
}
/* determine row type and set bounds */
if (lb <= XPRS_MINUSINFINITY && ub >= XPRS_PLUSINFINITY) {
rowtype = 'N';
CHECK_RETURN( XPRSchgrowtype(prob, 1, &i, &rowtype) );
} else {
if (lb <= XPRS_MINUSINFINITY) {
rowtype = 'L';
CHECK_RETURN( XPRSchgrowtype(prob, 1, &i, &rowtype) );
CHECK_RETURN( XPRSchgrhs(prob, 1, &i, &ub) );
} else {
if (ub >= XPRS_PLUSINFINITY) {
rowtype = 'G';
CHECK_RETURN( XPRSchgrowtype(prob, 1, &i, &rowtype) );
CHECK_RETURN( XPRSchgrhs(prob, 1, &i, &lb) );
} else {
if (lb == ub) {
rowtype = 'E';
CHECK_RETURN( XPRSchgrowtype(prob, 1, &i, &rowtype) );
CHECK_RETURN( XPRSchgrhs(prob, 1, &i, &ub) );
} else {
rowtype = 'L';
CHECK_RETURN( XPRSchgrowtype(prob, 1, &i, &rowtype) );
CHECK_RETURN( XPRSchgrhs(prob, 1, &i, &ub) );
range = ub-lb;
CHECK_RETURN( XPRSchgrhsrange(prob, 1, &i, &range) );
}
}
}
}
cleanup:
return returnCode;
}
/*
This function calculates the infeasibilities of a solution (i.e. the values
of the feasibility breakers after a repairinfeas call)
*/
int Getinfeasibilitybreakers(XPRSprob prob, const double *x,
const double *slacks, double constraints[],
double bounds[], const double tolarence) {
int returnCode = 0;
int i, j, ncols, nrows;
double rhs, activity;
double lb, ub;
/* get problem dimensions */
CHECK_RETURN( XPRSgetintattrib(prob, XPRS_INPUTROWS, &nrows) );
CHECK_RETURN( XPRSgetintattrib(prob, XPRS_INPUTCOLS, &ncols) );
/* check constraints */
for (i=0; i<nrows; i++) {
CHECK_RETURN( XPRSgetrhs(prob, &rhs, i, i) );
activity = rhs - slacks[i];
CHECK_RETURN( Getrowbounds(prob, i, &lb, &ub) );
if (activity < lb-tolarence) {
constraints[i] = activity-lb; /* a negative value indicates that the
lower bound is relaxed */
} else
if (activity > ub+tolarence) {
constraints[i] = activity-ub; /* a positive value indicates that the
upper bound is relaxed */
} else {
constraints[i] = 0.0;
}
}
/* check bounds */
for (j=0; j<ncols; j++) {
CHECK_RETURN( XPRSgetlb(prob, &lb, j, j) );
CHECK_RETURN( XPRSgetub(prob, &ub, j, j) );
if (x[j] < lb-tolarence) {
bounds[j] = x[j]-lb; /* a negative value indicates that the lower bound
is relaxed */
} else {
if (x[j] > ub+tolarence) {
bounds[j] = x[j]-ub; /* a positive value indicates that the upper
bound is relaxed */
} else {
bounds[j] = 0.0;
}
}
}
cleanup:
return returnCode;
}
/* This function just converts a double to a string for reporting, converting
infinity values as "NONE" */
void Bound_to_string(double bound, char *string) {
if (bound > XPRS_MINUSINFINITY && bound < XPRS_PLUSINFINITY) {
if (bound >= 0)
sprintf(string, " %.5e", bound);
else
sprintf(string, "%.5e", bound);
} else {
memcpy(string," NONE \0", 14);
}
}
/*
Prints a summary of the infeasibily breakers using the already calculated
infeasibities
*/
int Generatefeasibilityreport(XPRSprob prob, const double
*constraintviolations,
const double *boundviolations) {
int returnCode = 0;
int i, j;
int nrows, ncols;
double suminf = 0; /* Sum if infeasibility */
int ninf = 0; /* Number of rows and columns
reapired */
int len, NameLength; /* Name lengths in the LP file */
char *name = NULL;
double lb, ub;
char slb[25], sub[25]; /* Fixed length name buffers */
char slbshift[25], subshift[25];
/* Get name lengths */
CHECK_RETURN( XPRSgetintattrib(prob, XPRS_INPUTROWS, &nrows) );
CHECK_RETURN( XPRSgetintattrib(prob, XPRS_INPUTCOLS, &ncols) );
/* Get the maximum name length */
NameLength = 0;
for(i=0;i<nrows;i++) {
CHECK_RETURN( XPRSgetnamelist(prob, 1, NULL, 0, &len, i, i) );
if (len>NameLength)
NameLength=len;
}
for(i=0;i<ncols;i++) {
CHECK_RETURN( XPRSgetnamelist(prob, 2, NULL, 0, &len, i, i) );
if (len>NameLength)
NameLength=len;
}
/* Allocate name buffer */
name = malloc(NameLength);
if (!name) {
perror("malloc");
returnCode = -2;
goto cleanup;
}
printf("\n");
printf("\n");
printf("XPRESS-MP FEASIBILITY REPAIR REPORT.\n");
printf("\n");
printf("The following constraints were repaired.\n");
printf("\n");
printf("Index Name%*s Lower bound Repaired Upper bound Repaired \n", NameLength-4,"");
for (i=0; i<nrows; i++) {
if (constraintviolations[i] != 0) {
/* get constraint name */
CHECK_RETURN( XPRSgetnamelist(prob, 1, name, NameLength, NULL, i, i) );
CHECK_RETURN( Getrowbounds(prob, i, &lb, &ub) );
Bound_to_string(lb, slb); Bound_to_string(ub, sub);
suminf += fabs(constraintviolations[i]);
ninf++;
if (constraintviolations[i] < 0) {
Bound_to_string(lb+constraintviolations[i], slbshift);
Bound_to_string(ub, subshift);
} else {
Bound_to_string(lb, slbshift);
Bound_to_string(ub+constraintviolations[i], subshift);
}
printf("%.5i %*s %*s %*s %*s %*s\n", i, NameLength, name, 7, slb,
7, slbshift, 7, sub, 7, subshift);
}
}
printf("\n");
printf("The following bound constraints were repaired.\n");
printf("\n");
printf("Index Name%*s Lower bound Repaired Upper bound Repaired \n", NameLength-4,"");
for (j=0; j<ncols; j++) {
if (boundviolations[j] != 0) {
/* get constraint name */
CHECK_RETURN( XPRSgetnamelist(prob, 2, name, NameLength, NULL, j, j) );
CHECK_RETURN( XPRSgetlb(prob, &lb, j, j) );
CHECK_RETURN( XPRSgetub(prob, &ub, j, j) );
Bound_to_string(lb, slb); Bound_to_string(ub, sub);
suminf += fabs(boundviolations[j]);
ninf++;
if (constraintviolations[j] < 0) {
Bound_to_string(boundviolations[j], slbshift);
Bound_to_string(ub, subshift);
} else {
Bound_to_string(lb, slbshift);
Bound_to_string(boundviolations[j], subshift);
}
printf("%.5i %*s %*s %*s %*s %*s\n", j, NameLength, name, 7, slb,
7, slbshift, 7, sub, 7, subshift);
}
}
printf("\n");
printf("Sum of Violations %f\n", suminf);
printf("Number of corrections: %i\n", ninf);
printf("\n");
cleanup:
free(name);
return returnCode;
}
/*
Relaxes the problem given the values of the feasibility breakers
*/
int Applyrepairinfeasresulttoproblem(XPRSprob prob,
const double *constraintviolations,
const double *boundviolations)
{
int returnCode = 0;
int i, j;
int nrows, ncols;
char boundtype;
double lb, ub;
/* Get name lengths */
CHECK_RETURN( XPRSgetintattrib(prob, XPRS_INPUTROWS, &nrows) );
CHECK_RETURN( XPRSgetintattrib(prob, XPRS_INPUTCOLS, &ncols) );
/* apply changes to rows */
for (i=0; i<nrows; i++) {
if (constraintviolations[i] != 0) {
/* get constraint name */
CHECK_RETURN( Getrowbounds(prob, i, &lb, &ub) );
/* apply relaxation */
if (constraintviolations[i] > 0) {
ub += constraintviolations[i];
} else {
lb += constraintviolations[i];
}
CHECK_RETURN( Setrowbounds(prob, i, lb, ub) );
}
}
/* apply changes to columns */
for (j=0; j<ncols; j++) {
if (boundviolations[j] != 0) {
/* get constraint name */
CHECK_RETURN( XPRSgetlb(prob, &lb, j, j) );
CHECK_RETURN( XPRSgetub(prob, &ub, j, j) );
if (boundviolations[j] > 0) {
boundtype = 'U';
ub += boundviolations[j];
CHECK_RETURN( XPRSchgbounds(prob, 1, &j, &boundtype, &ub) );
} else {
boundtype = 'L';
lb += boundviolations[j];
CHECK_RETURN( XPRSchgbounds(prob, 1, &j, &boundtype, &lb) );
}
}
}
printf("\n");
printf("Problem repaired.");
printf("\n");
cleanup:
return returnCode;
}
/* XPRS optimizer message callback */
void XPRS_CC messagecb(XPRSprob cbprob, void* cbdata,
const char *msg, int len, int msgtype)
{
(void)cbprob; /* unused (the problem for which the message is issued) */
(void)cbdata; /* unused (the data passed to XPRSaddcbmessage()) */
switch(msgtype)
{
case 4: /* error */
case 3: /* warning */
case 2: /* not used */
case 1: /* information */
printf("%*s\n", len, msg);
break;
default: /* exiting - buffers need flushing */
fflush(stdout);
break;
}
}
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