/*********************************************************************** Xpress Optimizer Examples ========================= file mipsolpool.c ````````````````` Generate all solutions with the MIP solution pool We take the power generation problem stored in hpw15.mps which seeks to optimise the operating pattern of a group of electricity generators. We solve the problem collecting all solutions found during the MIP search. The optimal solution's objective and solution values are printed to screen. (c) 2017-2025 Fair Isaac Corporation ***********************************************************************/ #include <stdio.h>
#include <stdlib.h> #include "xprs.h" /* Optimizer header file */ /* Define were data is located. */ #ifndef DATADIR # define DATADIR "../data" #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) static void XPRS_CC messagecb(XPRSprob cbprob, void* cbdata, const char *msg, int len, int msgtype); int main(void) { int returnCode = 0; XPRSprob prob = NULL; XPRSmipsolpool msp = NULL; int i, nSols, nCols, iSolutionId, iSolutionIdStatus; double dObj, dSol; const char *sProblem = DATADIR"/hpw15"; /* 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) ); CHECK_RETURN( XPRS_msp_create(&msp) ); CHECK_RETURN( XPRS_msp_probattach(msp, prob) ); CHECK_RETURN( XPRSreadprob(prob, sProblem, "") ); CHECK_RETURN( XPRSmipoptimize(prob, "") ); CHECK_RETURN( XPRS_msp_getintattrib(msp, XPRS_MSP_SOLUTIONS, &nSols) ); if(nSols) { CHECK_RETURN( XPRS_msp_getdblattribprobextreme(msp, prob, 0, &iSolutionId, XPRS_MSP_SOLPRB_OBJ, &dObj) ); printf("Optimal Solution ID: %i\n", iSolutionId); printf("Optimal Objective : %12,5f\n", dObj); CHECK_RETURN( XPRS_msp_getintattribsol(msp, iSolutionId, &iSolutionIdStatus, XPRS_MSP_SOL_COLS, &nCols) ); for(i = 0; i < nCols; i++) { CHECK_RETURN( XPRS_msp_getsol(msp, iSolutionId, &iSolutionIdStatus, &dSol, i, i, NULL) ); printf("%3i = %12,5f\n", i, dSol); } } 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). */ XPRSdestroyprob(prob); XPRS_msp_destroy(msp); XPRSfree(); 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; } }