Problem Attributes
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_. It is possible to use the above functions with 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:
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Number of nonlinear coefficients
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Current value of penalty cost multiplier for penalty delta vectors
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Current value of penalty cost multiplier for penalty error vectors
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Number of character variables
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Number of delta vectors created during augmentation
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Number of infeasible constraints found at the point of linearization
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Index of the reserved "=" column
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Total penalty costs in the solution
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Number of variables with an exploration-type delta set up in the problem
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Number of internal functions
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Number of SLP variables appearing only in coefficients
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Number of variables set up with an integer delta in the problem
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Number of calls made to internal functions
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SLP iteration count
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Unique identifier for the current job
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The iteration in which the returned solution has been found.
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Xpress NonLinear minor version number
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Number of negative penalty error vectors
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Total number of SLP iterations in MISLP
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Number of nodes explored in MISLP. This includes any nodes for which a non-linear solve has been carried out.
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The underlying Optimizer MIP problem. XSLP_MIPPROBLEM is a reference of type XPRSprob, and should be used in MISLP callbacks to access MIP-specific Optimizer values (such as node and parent numbers).
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Number of integer solutions found in MISLP. This includes solutions found during the tree search or any heuristics.
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Number of model columns in the problem
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Number of model rows in the problem
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Status of the mutlistart search
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The solution status of the problem.
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Number of coefficients in the augmented problem that might change between SLP iterations
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Number of nonlinear constraints in the problem
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Objective function value excluding any penalty costs
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Number of model columns in the problem
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Number of model rows in the problem
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Index of column costing the penalty delta row
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Index of equality row holding the penalties for delta vectors
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Number of penalty delta vectors
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Total activity of penalty delta vectors
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Total penalty cost attributed to penalty delta vectors
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Index of column costing the penalty error row
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Index of equality row holding the penalties for penalty error vectors
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Number of penalty error vectors
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Total activity of penalty error vectors
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Total penalty cost attributed to penalty error vectors
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Number of positive penalty error vectors
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Number of potential delta variables deleted by
XSLPpresolve
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Number of SLP variables eliminated by
XSLPpresolve
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Number of SLP coefficients fixed by
XSLPpresolve
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Number of determining rows fixed by
XSLPpresolve
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Number of variables fixed to a nonzero value by
XSLPpresolve
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Number of SLP variables fixed by
XSLPpresolve
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Number of variables fixed at zero by
XSLPpresolve
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Number of passes made by the SLP nonlinear presolve procedure
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Indicates if the problem is presolved
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Number of bounds tightened by
XSLPpresolve
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Local primal integral of the solve
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Number of step-bounded variables converged only on extended criteria
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Number of variables with a minimum perturbation step set up in the problem
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Indicates the type of solution returned by the solver.
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The underlying solution pool. XSLP_SOLUTIONPOOL is a reference of type XPRSmipsolpool. Change control
XSLP_ANALYZE to record the solutions into the pool.
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Includes information of which Xpress solver has been used to solve the problem
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Bitmap holding the problem convergence status
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Status of the optimization process.
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Number of tolerance sets
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The total number of evaluation errors during the solve
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Number of unconverged variables with coefficients in constraining rows
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Number of user function instances
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Number of user functions
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Number of unconverged values
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Indicates whether numeric or analytic derivatives were used to create the linear approximations and solve the problem
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Number of calls made to user functions
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Absolute validation index
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Relative first order optimality validation index
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Relative validation index
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Number of SLP variables
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Xpress NonLinear major version number
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Date of creation of Xpress NonLinear
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Vertex solution index
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The underlying Optimizer problem
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The Xpress NonLinear problem
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Number of placeholder entries set to zero
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Number of potentially zero placeholders left untouched
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Number of potential zero placeholder entries
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