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8  xpProblemAttrib - Problem Attributes

Description
During the optimization process, various properties of the problem being solved are stored and made available to users of TOMLAB /Xpress in the form of problem attributes. These can be accessed in the global structure xpProblemAttrib. A full list of the attributes available and their types may be found in this Section.

The following problem attributes are available after optimization:

Symbol	Description
ACTIVENODES	Number of outstanding nodes.
BARAASIZE	Number of nonzeros in AAT.
BARCROSSOVER	Indicates whether or not the basis crossover phase has been entered.
	0 = The crossover phase has not been entered.
	1 = The crossover phase has been entered.
BARDENSECOL	Number of dense columns found in the matrix.
BARDUALINF	Sum of the dual infeasibilities for the Newton barrier algorithm.
BARDUALOBJ	Dual objective value calculated by the Newton barrier algorithm.
BARITER	Number of Newton barrier iterations.
BARLSIZE	Number of nonzeros in L resulting from the Cholesky factorization.
BARPRIMALINF	Sum of the primal infeasibilities for the Newton barrier algorithm.
BARPRIMALOBJ	Primal objective value calculated by the Newton barrier algorithm.
BARSTOP	Convergence criterion for the Newton barrier algorithm.
BESTBOUND	Value of the best bound determined so far by the global search.
BOUNDNAME	Active bound name.
BRANCHVALUE	The value of the branching variable at a node of the Branch and Bound tree.
COLS	Number of columns (i.e. variables) in the matrix.
	Note: If the matrix is in a presolved state, this attribute returns the number of columns in the presolved matrix. If you require the value for the original matrix, make sure you obtain the value when the matrix is not presolved. The PRESOLVESTATE attribute can be used to test if the matrix is presolved or not. See also Working with Presolve.
CUTS	Number of cuts being added to the matrix.
DUALINFEAS	Number of dual infeasibilities.
	Note: If the matrix is in a presolved state, this attribute returns the number of dual infeasibilities in the presolved matrix. If you require the value for the original matrix, make sure you obtain the value when the matrix is not presolved. The PRESOLVESTATE attribute can be used to test if the matrix is presolved or not. See also Working with Presolve.
ELEMS	Number of matrix nonzeros (elements).
	If the matrix is in a presolved state, this attribute returns the number of matrix nonzeros in the presolved matrix. If you require the value for the original matrix, make sure you obtain the value when the matrix is not presolved. The PRESOLVESTATE attribute can be used to test if the matrix is presolved or not. See also Working with Presolve.
ERRORCODE	The most recent Optimizer error number that occurred. This is useful to determine the precise error or warning that has occurred, after an Optimizer function has signalled an error by returning a non-zero value. The return value itself is not the error number. Refer to Xpress manual available from http://tomopt.com is an error should occur.
IIS	Number of IIS found.
LPOBJVAL	Value of the objective function of the last LP solved.
LPSTATUS	LP solution status.
	1 = Optimal.
	2 = Infeasible.
	3 = Objective worse than cutoff.
	4 = Unfinished.
	5 = Unbounded.
	6 = Cutoff in dual.
MATRIXNAME	The matrix name.
	Note: This is the name read from the MATRIX field in an MPS matrix, and is not related to the problem name used in the Optimizer.
MIPENTS	Number of global entities (i.e. binary, integer, semi-continuous, partial integer, and semi-continuous integer variables) but excluding the number of special ordered sets.
	Note: If the matrix is in a presolved state, this attribute returns the number of global entities in the presolved matrix. If you require the value for the original matrix, make sure you obtain the value when the matrix is not presolved. The PRESOLVESTATE attribute can be used to test if the matrix is presolved or not. See also Working with Presolve.
MIPINFEAS	Number of integer infeasibilities at the current node.
MIPOBJVAL	Objective function value of the best integer solution found.
MIPSOLNODE	Node at which the last integer feasible solution was found.
MIPSOLS	Number of integer solutions that have been found.
MIPSTATUS	Global (MIP) solution status.
	1 = Problem has not been loaded.
	2 = LP has not been optimized.
	3 = LP has been optimized. Once the MIP optimization proper has begun, only the following four status codes will be returned.
	4 = Global search incomplete - no integer solution found.
	5 = Global search incomplete - an integer solution has been found.
	6 = Global search complete - no integer solution found.
	7 = Global search complete - integer solution found.
	Note: If a 3 status code is returned, it implies that the optimization halted during or directly after the LP optimization - for instance, if the LP relaxation is infeasible or unbounded. In this case please check the value of LP solution status using LPSTATUS.
NAMELENGTH	The length (in 8 character units) of row and column names in the matrix. To allocate a character array to store names, you must allow 8*NAMELENGTH+1 characters per name (the +1 allows for the string terminator character).
NODEDEPTH	Depth of the current node.
NODES	Number of nodes solved so far in the global search. The node numbers start at 1 for the first (top) node in the Branch and Bound tree. Nodes are numbered consecutively.
OBJFIXED	Contribution to the objective function from artificial (fixed) variables.
	Note: If the matrix is in a presolved state, this attribute returns the contribution to the objective from the artificial variables in the presolved matrix. If you require the value for the original matrix, make sure you obtain the value when the matrix is not presolved. The PRESOLVESTATE attribute can be used to test if the matrix is presolved or not. See also Working with Presolve.
OBJNAME	Active objective function row name.
OBJRHS	Fixed part of the objective function.
	Note: If the matrix is in a presolved state, this attribute returns the fixed part of the objective in the presolved matrix. If you require the value for the original matrix, make sure you obtain the value when the matrix is not presolved. The PRESOLVESTATE attribute can be used to test if the matrix is presolved or not. See also Working with Presolve.
OBJSENSE	Sense of the optimization being performed.
	1.0 = For minimization problems.
	-1.0 = For maximization problems.
PARENTNODE	The parent node of the current node in the tree search.
PRESOLVESTATE	Problem status as a bit map.
	0 = Problem has been loaded.
	1 = Problem has been LP presolved.
	2 = Problem has been MIP presolved.
	7 = Solution in memory is valid.
PRIMALINFEAS	Number of primal infeasibilities.
	Note: If the matrix is in a presolved state, this attribute returns the number of primal infeasibilities in the presolved matrix. If you require the value for the original matrix, make sure you obtain the value when the matrix is not presolved. The PRESOLVESTATE attribute can be used to test if the matrix is presolved or not. See also Working with Presolve.
QELEMS	Number of quadratic elements in the matrix.
	If the matrix is in a presolved state, this attribute returns the number of quadratic elements in the presolved matrix. If you require the value for the original matrix, make sure you obtain the value when the matrix is not presolved. The PRESOLVESTATE attribute can be used to test if the matrix is presolved or not. See also Working with Presolve.
RANGENAME	Active range name.
RHSNAME	Active right hand side name.
ROWS	Number of rows (i.e. constraints) in the matrix.
	Note: If the matrix is in a presolved state, this attribute returns the number of rows in the presolved matrix. If you require the value for the original matrix, make sure you obtain the value when the matrix is not presolved. The PRESOLVESTATE attribute can be used to test if the matrix is presolved or not. See also Working with Presolve.
SIMPLEXITER	Number of simplex iterations performed.
SETMEMBERS	Number of variables within special ordered sets (set members) in the matrix.
	Note: If the matrix is in a presolved state, this attribute returns the number of variables within special ordered sets in the presolved matrix. If you require the value for the original matrix, make sure you obtain the value when the matrix is not presolved. The PRESOLVESTATE attribute can be used to test if the matrix is presolved or not. See also Working with Presolve.
SETS	Number of special ordered sets in the matrix.
	Note: If the matrix is in a presolved state, this attribute returns the number of special ordered sets in the presolved matrix. If you require the value for the original matrix, make sure you obtain the value when the matrix is not presolved. The PRESOLVESTATE attribute can be used to test if the matrix is presolved or not. See also Working with Presolve.
SPARECOLS	Number of spare columns in the matrix.
SPAREELEMS	Number of spare matrix elements in the matrix.
SPAREMIPENTS	Number of spare global entities in the matrix.
SPAREROWS	Number of spare rows in the matrix.
SUMPRIMALINF	Scaled sum of primal infeasibilities.
	If the matrix is in a presolved state, this attribute returns the scaled sum of primal infeasibilities in the presolved matrix. If you require the value for the original matrix, make sure you obtain the value when the matrix is not presolved. The PRESOLVESTATE attribute can be used to test if the matrix is presolved or not. See also Working with Presolve.

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