/***********************************************************************
Xpress Optimizer Examples
=========================
file addmipsol.c
````````````````
Implement a rounding type heuristic in the optnode callback
to demonstrate how to load solutions into the optimizer.
(c) 2017-2024 Fair Isaac Corporation
***********************************************************************/
#include <stdlib.h>
#include <stdio.h>
#include <memory.h>
#include <string.h>
#include <math.h>
#include "xprs.h"
#if defined(WIN32) || defined(_WIN32)
#include <windows.h>
#else
#include <pthread.h>
#endif
/* 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)
typedef struct {
char sProbName[256];
int nCol; /* Number of columns */
/* Global problem information */
int nGlEnt; /* Number of global entities: binary,
integer, semi-continuous and partial
integer variables */
int nSet; /* Number of S1 and S2 sets */
int *pGlInd; /* Column indices of the global entities
*/
char *pGlType; /* Global entity types */
} FixedSearchMainContext;
typedef struct {
char sProbName[256];
int nCol; /* Number of columns */
/* Global problem information */
int nGlEnt; /* Number of global entities: binary,
integer, semi-continuous and partial
integer variables */
int nSet; /* Number of S1 and S2 sets */
int *pGlInd; /* Column indices of the global entities
*/
char *pGlType; /* Global entity types */
/* Bound changes */
int *pBndInd; /* Column indices of the bounds to be
changed */
char *pBndType; /* New bound types - always 'B', since
both the upper and lower bounds are to
be changed */
double *pBndVal; /* New bound values */
/* Solution information */
double *x; /* MIP and LP solution values */
} FixedSearchLocalContext;
void *GetCurrentThreadHandle()
{
#if defined(WIN32) || defined(_WIN32)
return (void *) GetCurrentThreadId();
#else
return (void *) pthread_self();
#endif
}
/* XPRS optimizer message callback */
static 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;
}
}
int AllocateLocalContext(FixedSearchMainContext *MainContext,
FixedSearchLocalContext *LocalContext)
{
int returnCode = 0;
LocalContext->pGlInd = MainContext->pGlInd;
LocalContext->pGlType = MainContext->pGlType;
memcpy(LocalContext->sProbName, MainContext->sProbName,
sizeof(LocalContext->sProbName));
LocalContext->nCol = MainContext->nCol;
LocalContext->nGlEnt = MainContext->nGlEnt;
LocalContext->nSet = MainContext->nSet;
/* Allocate memory for MIP solution array and bound arrays */
LocalContext->x=malloc(LocalContext->nCol * sizeof(*LocalContext->x));
LocalContext->pBndInd=malloc(LocalContext->nGlEnt *
sizeof(*LocalContext->pBndInd));
LocalContext->pBndVal=malloc(LocalContext->nGlEnt *
sizeof(*LocalContext->pBndVal));
LocalContext->pBndType=malloc(LocalContext->nGlEnt *
sizeof(*LocalContext->pBndType));
if (!LocalContext->x || !LocalContext->pBndInd ||
!LocalContext->pBndVal || !LocalContext->pBndType)
{
perror("malloc");
returnCode = -2;
goto cleanup;
}
cleanup:
return returnCode;
}
void FreeLocalContext(FixedSearchLocalContext *LocalContext)
{
free(LocalContext->x);
free(LocalContext->pBndInd);
free(LocalContext->pBndVal);
free(LocalContext->pBndType);
}
int AllocateMainContext(XPRSprob prob, FixedSearchMainContext *Context)
{
int returnCode = 0;
CHECK_RETURN( XPRSgetprobname(prob, Context->sProbName) );
CHECK_RETURN( XPRSgetintattrib(prob, XPRS_COLS, &Context->nCol) );
CHECK_RETURN( XPRSgetintattrib(prob, XPRS_MIPENTS, &Context->nGlEnt) );
CHECK_RETURN( XPRSgetintattrib(prob, XPRS_SETS, &Context->nSet) );
/* Allocate memory for global entity arrays */
Context->pGlInd=malloc(Context->nCol * sizeof(*Context->pGlInd));
Context->pGlType=malloc(Context->nCol * sizeof(*Context->pGlType));
if (!Context->pGlInd || !Context->pGlType) {
perror("malloc");
returnCode = -2;
goto cleanup;
}
/* Retrieve global entity information */
CHECK_RETURN( XPRSgetmipentities(prob, &Context->nGlEnt, &Context->nSet,
Context->pGlType, Context->pGlInd,
NULL, NULL, NULL, NULL, NULL) );
cleanup:
return returnCode;
}
void FreeMainContext(FixedSearchMainContext *Context)
{
free(Context->pGlInd);
free(Context->pGlType);
}
int FixedSearch(XPRSprob parent, FixedSearchMainContext *MainContext)
{
int returnCode = 0;
int nBnd, i, j, iMipInfeas, iMipSols, bHasMipIncumbent, nOptnodeCalled;
XPRSprob probg = NULL, emptyprob = NULL;
double dRounded, dMipTol, dMipIncumbent;
char sTempProbName[256 + 32 + 1];
FixedSearchLocalContext LocalContext;
/* Only run once per node (since adding a solution will call the callback to
be fired again) */
CHECK_RETURN( XPRSgetintattrib(parent, XPRS_CALLBACKCOUNT_OPTNODE,
&nOptnodeCalled) );
if(nOptnodeCalled > 1) {
goto cleanup;
}
/* Only run the search for solutions with small numbers of integer
infeasibilities */
CHECK_RETURN( XPRSgetintattrib(parent, XPRS_MIPINFEAS, &iMipInfeas) );
if(iMipInfeas > 0.25*MainContext->nGlEnt) {
goto cleanup;
}
/* Create resources we need */
CHECK_RETURN( AllocateLocalContext(MainContext, &LocalContext) );
/* Create a problem containing the original problem */
CHECK_RETURN( XPRScreateprob(&probg) );
CHECK_RETURN( XPRScopyprob(probg, parent, LocalContext.sProbName) );
CHECK_RETURN( XPRSpostsolve(probg) );
/* Reset the controls of the problem and restore the name of the problem */
CHECK_RETURN( XPRScreateprob(&emptyprob) );
CHECK_RETURN( XPRScopycontrols(probg, emptyprob) );
XPRSdestroyprob(emptyprob);
/* Rename the problem so we don't get collisions with temporary files
produced by the optimizer */
sprintf(sTempProbName, "%s_%p", LocalContext.sProbName,
GetCurrentThreadHandle());
CHECK_RETURN( XPRSsetprobname(probg, sTempProbName) );
/* Tell Optimizer to call Message whenever a message is output */
CHECK_RETURN( XPRSaddcbmessage(probg, messagecb, &LocalContext, 0) );
/* Get information from the solution at the current node of 'parent' problem
*/
CHECK_RETURN( XPRSgetintattrib(parent, XPRS_MIPSOLS, &bHasMipIncumbent) );
CHECK_RETURN( XPRSgetdblattrib(parent, XPRS_MIPOBJVAL, &dMipIncumbent) );
CHECK_RETURN( XPRSgetcallbacksolution(parent, NULL, LocalContext.x, 0, LocalContext.nCol - 1) );
/* Initialise bound counter */
nBnd = 0;
CHECK_RETURN( XPRSgetdblcontrol(parent, XPRS_MIPTOL, &dMipTol) );
/* Go through global entities */
for(i=0; i<LocalContext.nGlEnt; i++) {
/* Test whether each is a binary or integer variable */
if (LocalContext.pGlType[i] == 'B' || LocalContext.pGlType[i] == 'I') {
j = LocalContext.pGlInd[i];
/* Fix variables that are fractional */
dRounded = (double) (int)(LocalContext.x[j]+0.5);
if(fabs(dRounded - LocalContext.x[j]) <= dMipTol) {
continue;
}
LocalContext.pBndInd[nBnd] = j;
LocalContext.pBndVal[nBnd] = dRounded;
LocalContext.pBndType[nBnd] = 'B';
nBnd++;
}
}
/* Instruct Optimizer to change the bounds */
CHECK_RETURN( XPRSchgbounds(probg, nBnd, LocalContext.pBndInd,
LocalContext.pBndType, LocalContext.pBndVal) );
printf("%p:After global the %d binary and integer variables were fixed\n",
GetCurrentThreadHandle(), nBnd);
/*
Ensure we only do a small search in the fixed problem and
use the current incumbent objective from the main problem
*/
CHECK_RETURN( XPRSsetintcontrol(probg, XPRS_MAXNODE, 100) );
CHECK_RETURN( XPRSsetintcontrol(probg, XPRS_MAXMIPSOL, 1) );
if(bHasMipIncumbent) {
/* Set a cut-off to help the fixed search */
CHECK_RETURN( XPRSsetdblcontrol(probg, XPRS_MIPABSCUTOFF, dMipIncumbent) );
}
CHECK_RETURN( XPRSsetintcontrol(probg, XPRS_MIPLOG, 3) );
/* Read the basis for the LP relaxation to reduce run time */
CHECK_RETURN( XPRSreadbasis(probg, LocalContext.sProbName,"") );
/* Run the optimizer */
CHECK_RETURN( XPRSmipoptimize(probg,"") );
/* If we found a solution then load it into the main problem */
CHECK_RETURN( XPRSgetintattrib(probg, XPRS_MIPSOLS, &iMipSols) );
if(iMipSols > 0) {
CHECK_RETURN( XPRSgetsolution(probg, NULL, LocalContext.x, 0, LocalContext.nCol - 1) );
CHECK_RETURN( XPRSaddmipsol(parent, LocalContext.nCol, LocalContext.x,
NULL, NULL) );
}
/* Free the resources we have created */
XPRSdestroyprob(probg);
FreeLocalContext(&LocalContext);
cleanup:
return returnCode;
}
void XPRS_CC OptNodeCb(XPRSprob my_prob, void *my_object, int *feas)
{
FixedSearchMainContext *Context = my_object;
(void)feas; /* unused */
FixedSearch(my_prob, Context);
}
int main(void) {
int returnCode = 0;
XPRSprob prob = NULL;
const char *sProbName = "../data/addmipsol";
FixedSearchMainContext Context;
memset(&Context, 0, sizeof(Context));
/* 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, &Context, 0) );
CHECK_RETURN( XPRSreadprob(prob, sProbName,"") );
/* Register the fixed search routine to the optimal node callback */
CHECK_RETURN( XPRSaddcboptnode(prob, OptNodeCb, &Context, 0) );
/* Make the problem difficult for the optimizer to solve */
CHECK_RETURN( XPRSsetintcontrol(prob, XPRS_CUTSTRATEGY,
XPRS_CUTSTRATEGY_NONE) );
CHECK_RETURN( XPRSsetintcontrol(prob, XPRS_HEUREMPHASIS, 0) );
CHECK_RETURN( XPRSsetintcontrol(prob, XPRS_SBBEST, 0) );
CHECK_RETURN( XPRSsetintcontrol(prob, XPRS_MIPTHREADS, 20) );
/* Log every node in the branch-and-bound search */
CHECK_RETURN( XPRSsetintcontrol(prob, XPRS_MIPLOG, 3) );
/* Setup some resources we need in the callbacks */
CHECK_RETURN( AllocateMainContext(prob, &Context) );
/* Solve the root node relaxation and write out the basis (to reduce solve
time of the fixed problems) */
CHECK_RETURN( XPRSmipoptimize(prob,"l") );
CHECK_RETURN( XPRSwritebasis(prob,"","") );
/* Run the MIP search */
CHECK_RETURN( XPRSmipoptimize(prob, "") );
cleanup:
if (returnCode > 0) {
/* There was an error. 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).
*/
FreeMainContext(&Context);
XPRSdestroyprob(prob);
XPRSfree();
return returnCode;
}
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