Problem Attributes

Topics covered in this chapter:

During the optimization process, various properties of the problem being solved are stored and made available to users of the Xpress NonLinear Libraries in the form of problem attributes. These can be accessed in much the same manner as the controls. Examples of problem attributes include the sizes of arrays, for which library users may need to allocate space before the arrays themselves are retrieved. A full list of the attributes available and their types may be found in this chapter.

Library users are provided with the following functions for obtaining the values of attributes:


XSLPgetintattrib	XSLPgetdblattrib
XSLPgetptrattrib	XSLPgetstrattrib

The attributes listed in this chapter are all prefixed with XSLP_. Most of them also exist within the Optimizer library with an NLP or SLP prefix, e.g., XPRS_NLPSOLSTATUS. It is possible to use the above functions with other attributes for the Xpress Optimizer (attributes prefixed with XPRS_). For details of the Optimizer attributes, see the Optimizer manual.

Example of the usage of the functions:

XSLPgetintattrib(Prob, XSLP_ITER, &nIter);
printf("The number of SLP iterations is %d\n", nIter);
XSLPgetdblattrib(Prob, XSLP_ERRORCOSTS, &Errors);
printf("and the total error cost is %lg\n", Errors);

The following is a list of all the Xpress NonLinear attributes:

XSLP_COEFFICIENTS, SLPCOEFFICIENTS	Number of nonlinear coefficients [ Problem Information, SLP]
XSLP_CURRENTDELTACOST, SLPCURRENTDELTACOST	Current value of penalty cost multiplier for penalty delta vectors [ SLP, Solution]
XSLP_CURRENTERRORCOST, SLPCURRENTERRORCOST	Current value of penalty cost multiplier for penalty error vectors [ SLP, Solution]
XSLP_DELTAS, SLPDELTAS	Number of delta vectors created during augmentation [ Problem Information, SLP]
XSLP_ECFCOUNT, SLPECFCOUNT	Number of infeasible constraints found at the point of linearization [ Linearizations, SLP]
XSLP_EQUALSCOLUMN, NLPEQUALSCOLUMN	Index of the reserved "=" column [ Problem Information]
XSLP_ERRORCOSTS, SLPERRORCOSTS	Total penalty costs in the solution [ SLP, Solution]
XSLP_EXPLOREDELTAS, SLPEXPLOREDELTAS	Number of variables with an exploration-type delta set up in the problem [ Problem Information, SLP]
XSLP_IFS, NLPIFS	Number of internal functions [ Misc]
XSLP_IMPLICITVARIABLES, NLPIMPLICITVARIABLES	Number of SLP variables appearing only in coefficients [ Problem Information, SLP]
XSLP_INTEGERDELTAS, SLPINTEGERDELTAS	Number of variables set up with an integer delta in the problem [ Problem Information, SLP]
XSLP_ITER, SLPITER	SLP iteration count [ Solution Process]
XSLP_JOBID, NLPJOBID	Unique identifier for the current job [ Misc, Multistart]
XSLP_KEEPBESTITER, NLPKEEPBESTITER	The iteration in which the returned solution has been found. [ SLP, Solution]
XSLP_MINUSPENALTYERRORS, SLPMINUSPENALTYERRORS	Number of negative penalty error vectors [ Problem Information, SLP]
XSLP_MIPITER, SLPMIPITER	Total number of SLP iterations in MISLP [ MISLP]
XSLP_MIPNODES, SLPMIPNODES	Number of nodes explored in MISLP. [ MISLP]
XSLP_MIPPROBLEM	The underlying Optimizer MIP problem. [ MISLP]
XSLP_MIPSOLS, SLPMIPSOLS	Number of integer solutions found in MISLP. [ MISLP, Solution]
XSLP_MODELCOLS, NLPMODELCOLS	Number of model columns in the problem [ SLP]
XSLP_MODELROWS, NLPMODELROWS	Number of model rows in the problem [ SLP]
XSLP_MSSTATUS	Status of the mutlistart search [ Multistart]
XSLP_NLPSTATUS, NLPSTATUS	The solution status of the problem. [ Solution Process]
XSLP_NONCONSTANTCOEFFS, SLPNONCONSTANTCOEFFS	Number of coefficients in the augmented problem that might change between SLP iterations [ SLP]
XSLP_NONLINEARCONSTRAINTS, NONLINEARCONSTRAINTS	Number of nonlinear constraints in the problem [ Problem Information]
XSLP_OBJVAL, NLPOBJVAL	Objective function value excluding any penalty costs [ Solution]
XSLP_OPTTIME, NLPOPTTIME	Time spent in optimization [ Solution Process]
XSLP_ORIGINALCOLS, NLPORIGINALCOLS	Number of model columns in the extended original problem [ Problem Information]
XSLP_ORIGINALROWS, NLPORIGINALROWS	Number of model rows in the extended original problem [ Problem Information]
XSLP_PENALTYDELTACOLUMN, SLPPENALTYDELTACOLUMN	Index of column costing the penalty delta row [ Problem Information, SLP]
XSLP_PENALTYDELTAROW, SLPPENALTYDELTAROW	Index of equality row holding the penalties for delta vectors [ Problem Information, SLP]
XSLP_PENALTYDELTAS, SLPPENALTYDELTAS	Number of penalty delta vectors [ Problem Information, SLP]
XSLP_PENALTYDELTATOTAL, SLPPENALTYDELTATOTAL	Total activity of penalty delta vectors [ SLP, Solution]
XSLP_PENALTYDELTAVALUE, SLPPENALTYDELTAVALUE	Total penalty cost attributed to penalty delta vectors [ SLP, Solution]
XSLP_PENALTYERRORCOLUMN, SLPPENALTYERRORCOLUMN	Index of column costing the penalty error row [ Problem Information, SLP]
XSLP_PENALTYERRORROW, SLPPENALTYERRORROW	Index of equality row holding the penalties for penalty error vectors [ Problem Information, SLP]
XSLP_PENALTYERRORS, SLPPENALTYERRORS	Number of penalty error vectors [ Problem Information, SLP]
XSLP_PENALTYERRORTOTAL, SLPPENALTYERRORTOTAL	Total activity of penalty error vectors [ SLP, Solution]
XSLP_PENALTYERRORVALUE, SLPPENALTYERRORVALUE	Total penalty cost attributed to penalty error vectors [ SLP, Solution]
XSLP_PLUSPENALTYERRORS, SLPPLUSPENALTYERRORS	Number of positive penalty error vectors [ Problem Information, SLP]
XSLP_PRESOLVEELIMINATIONS, NLPPRESOLVEELIMINATIONS	Number of SLP variables eliminated by XSLPpresolve [ Presolve]
XSLP_PRESOLVESTATE	Indicates if the problem is presolved [ Presolve]
XSLP_PRIMALINTEGRAL, NLPPRIMALINTEGRAL	Local primal integral of the solve [ Misc]
XSLP_SBXCONVERGED, SLPSBXCONVERGED	Number of step-bounded variables converged only on extended criteria [ SLP, SLP-convergence]
XSLP_SEMICONTDELTAS, SLPSEMICONTDELTAS	Number of variables with a minimum perturbation step set up in the problem [ Problem Information, SLP]
XSLP_SOLSTATUS, NLPSOLSTATUS	Indicates the type of solution returned by the solver. [ Solution]
XSLP_SOLVERSELECTED, LOCALSOLVERSELECTED	Includes information of which Xpress solver has been used to solve the problem [ Solution Process]
XSLP_STATUS, SLPSTATUS	Bitmap holding the problem convergence status [ Solution Process]
XSLP_STOPSTATUS, NLPSTOPSTATUS	Status of the optimization process. [ Solution Process]
XSLP_TOTALEVALUATIONERRORS, NLPTOTALEVALUATIONERRORS	The total number of evaluation errors during the solve [ Numerics]
XSLP_UCCONSTRAINEDCOUNT, SLPUCCONSTRAINEDCOUNT	Number of unconverged variables with coefficients in constraining rows [ SLP, SLP-convergence]
XSLP_UFINSTANCES	Number of user function instances [ User Functions]
XSLP_UFS, NLPUFS	Number of user functions [ User Functions]
XSLP_UNCONVERGED, SLPUNCONVERGED	Number of unconverged values [ SLP, SLP-convergence]
XSLP_USEDERIVATIVES, NLPUSEDERIVATIVES	Indicates whether numeric or analytic derivatives were used to create the linear approximations and solve the problem [ Derivatives]
XSLP_USERFUNCCALLS, NLPUSERFUNCCALLS	Number of calls made to user functions [ User Functions]
XSLP_VALIDATIONINDEX_A, NLPVALIDATIONINDEX_A	Absolute validation index [ Solution]
XSLP_VALIDATIONINDEX_K, NLPVALIDATIONINDEX_K	Relative first order optimality validation index [ Solution]
XSLP_VALIDATIONINDEX_R, NLPVALIDATIONINDEX_R	Relative validation index [ Solution]
XSLP_VALIDATIONNETOBJ, NLPVALIDATIONNETOBJ	Net objective as calculated by validation [ Solution]
XSLP_VALIDATIONSTATUS, NLPVALIDATIONSTATUS	Feasiblity status of the current solution. [ Solution]
XSLP_VARIABLES, NLPVARIABLES	Number of SLP variables [ Data Information, SLP]
XSLP_VERSIONDATE	Date of creation of Xpress NonLinear [ Misc]
XSLP_VSOLINDEX	Vertex solution index [ SLP, Solution]
XSLP_XPRSPROBLEM	The underlying Optimizer problem [ Misc]
XSLP_XSLPPROBLEM	The Xpress NonLinear problem [ Misc]
XSLP_ZEROESRESET, SLPZEROESRESET	Number of placeholder entries set to zero [ SLP]
XSLP_ZEROESRETAINED, SLPZEROESRETAINED	Number of potentially zero placeholders left untouched [ SLP]
XSLP_ZEROESTOTAL, SLPZEROESTOTAL	Number of potential zero placeholder entries [ SLP]

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Problem Attributes