Detailed Description

methods and files provided by the LP solver interface of SCIP

SCIP uses external tools to solve LP relaxations. The communication is realized through an LP interface.

This page lists public interface methods that every LP interface provides. Find the concrete implementation for your LP solver under "src/lpi/".

See also: Available implementations of the LP solver interface for a list of available LP solver interfaces

This file specifies a generic LP solver interface used by SCIP to create, modify, and solve linear programs of the form

min/max obj * x lhs <= A * x <= rhs lb <= x <= ub

and query information about the solution. Although it includes a few SCIP header files, e.g., because it uses SCIP's return codes, it can be used independently of any SCIP instance.

The basis status for (column) variables are as follows:

If x_j = lb, then j is at its lower bound (SCIP_BASESTAT_LOWER).
If x_j = ub, then j is at its lower bound (SCIP_BASESTAT_UPPER).
If x_j is in the basis, it has SCIP_BASESTAT_BASIC status.
If x_j is free and non-basic, it has SCIP_BASESTAT_ZERO status.

The basis status for (row) slack variables are:

If (A * x)_i = lhs, then i is at its lower bound (SCIP_BASESTAT_LOWER).
If (A * x)_i = rhs, then i is at its upper bound (SCIP_BASESTAT_UPPER).
If the slack variable for row i is basic, it has SCIP_BASESTAT_BASIC status.

If the solvers use their status differently, those status codes have to be corrected.

In the methods accessing information about the (inverse of the) basis matrix, the interface assumes the following column-oriented format: slack variables of rows have coefficient +1 and the basis matrix is a regular m times m submatrix of (A,I), where m is the number of rows and I is the identity matrix. This means that if, internally, the LP solver uses coefficients -1 for some of the slack variables, then every row associated with a slack variable whose coefficient is -1 should be negated in order to return the result in terms of the LP interface definition.

The creation of a new LP should always be done in the following ways: Either one can use SCIPlpiLoadColLP() or one first adds empty columns or rows. Then the matrix entries can be added by adding columns and rows, respectively. Adding matrix entries for a row or column that have not been added before will result in an error.

The handling of the objective limit is as follows, if supported by the LP-solver: If the objective is larger than the objective limit for minimization problems or smaller than the objective limit for maximization problems, the solution process can be stopped. This naturally occurs in a branch-and-bound process, where the objective limit is set to the value of the best solution found so far. If the problem is a minimization problem and we use the dual simplex, the dual feasible solutions are maximized. If their value are larger than the objective limit, the process can be stopped. In this case, no feasible integer solution can be found in the corresponding branch.

Some LP-solvers also support the opposite setting, but this can easily be checked after the solution process (i.e., for a minimization problem a check whether the optimal value is smaller than the limit). Note that this check can only be determined at the end of the optimization. Thus, we do not support this.

Files
file	lpi.h
	interface methods for specific LP solvers

Miscellaneous Methods
SCIP_EXPORT const char *	SCIPlpiGetSolverName (void)

SCIP_EXPORT const char *	SCIPlpiGetSolverDesc (void)

SCIP_EXPORT void *	SCIPlpiGetSolverPointer (SCIP_LPI *lpi)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiSetIntegralityInformation (SCIP_LPI lpi, int ncols, int intInfo)

SCIP_EXPORT SCIP_Bool	SCIPlpiHasPrimalSolve (void)

SCIP_EXPORT SCIP_Bool	SCIPlpiHasDualSolve (void)

SCIP_EXPORT SCIP_Bool	SCIPlpiHasBarrierSolve (void)

LPI Creation and Destruction Methods
SCIP_EXPORT SCIP_RETCODE	SCIPlpiCreate (SCIP_LPI *lpi, SCIP_MESSAGEHDLR messagehdlr, const char *name, SCIP_OBJSEN objsen)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiFree (SCIP_LPI **lpi)

Modification Methods
SCIP_EXPORT SCIP_RETCODE	SCIPlpiLoadColLP (SCIP_LPI lpi, SCIP_OBJSEN objsen, int ncols, const SCIP_Real obj, const SCIP_Real lb, const SCIP_Real ub, char *colnames, int nrows, const SCIP_Real lhs, const SCIP_Real rhs, char rownames, int nnonz, const int beg, const int ind, const SCIP_Real val)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiAddCols (SCIP_LPI lpi, int ncols, const SCIP_Real obj, const SCIP_Real lb, const SCIP_Real ub, char *colnames, int nnonz, const int beg, const int ind, const SCIP_Real val)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiDelCols (SCIP_LPI *lpi, int firstcol, int lastcol)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiDelColset (SCIP_LPI lpi, int dstat)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiAddRows (SCIP_LPI lpi, int nrows, const SCIP_Real lhs, const SCIP_Real rhs, char rownames, int nnonz, const int beg, const int ind, const SCIP_Real val)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiDelRows (SCIP_LPI *lpi, int firstrow, int lastrow)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiDelRowset (SCIP_LPI lpi, int dstat)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiClear (SCIP_LPI *lpi)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiChgBounds (SCIP_LPI lpi, int ncols, const int ind, const SCIP_Real lb, const SCIP_Real ub)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiChgSides (SCIP_LPI lpi, int nrows, const int ind, const SCIP_Real lhs, const SCIP_Real rhs)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiChgCoef (SCIP_LPI *lpi, int row, int col, SCIP_Real newval)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiChgObjsen (SCIP_LPI *lpi, SCIP_OBJSEN objsen)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiChgObj (SCIP_LPI lpi, int ncols, const int ind, const SCIP_Real *obj)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiScaleRow (SCIP_LPI *lpi, int row, SCIP_Real scaleval)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiScaleCol (SCIP_LPI *lpi, int col, SCIP_Real scaleval)

Data Accessing Methods
SCIP_EXPORT SCIP_RETCODE	SCIPlpiGetNRows (SCIP_LPI lpi, int nrows)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiGetNCols (SCIP_LPI lpi, int ncols)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiGetObjsen (SCIP_LPI lpi, SCIP_OBJSEN objsen)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiGetNNonz (SCIP_LPI lpi, int nnonz)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiGetCols (SCIP_LPI lpi, int firstcol, int lastcol, SCIP_Real lb, SCIP_Real ub, int nnonz, int beg, int ind, SCIP_Real *val)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiGetRows (SCIP_LPI lpi, int firstrow, int lastrow, SCIP_Real lhs, SCIP_Real rhs, int nnonz, int beg, int ind, SCIP_Real *val)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiGetColNames (SCIP_LPI lpi, int firstcol, int lastcol, char colnames, char namestorage, int namestoragesize, int *storageleft)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiGetRowNames (SCIP_LPI lpi, int firstrow, int lastrow, char rownames, char namestorage, int namestoragesize, int *storageleft)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiGetObj (SCIP_LPI lpi, int firstcol, int lastcol, SCIP_Real vals)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiGetBounds (SCIP_LPI lpi, int firstcol, int lastcol, SCIP_Real lbs, SCIP_Real *ubs)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiGetSides (SCIP_LPI lpi, int firstrow, int lastrow, SCIP_Real lhss, SCIP_Real *rhss)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiGetCoef (SCIP_LPI lpi, int row, int col, SCIP_Real val)

Solving Methods
SCIP_EXPORT SCIP_RETCODE	SCIPlpiSolvePrimal (SCIP_LPI *lpi)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiSolveDual (SCIP_LPI *lpi)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiSolveBarrier (SCIP_LPI *lpi, SCIP_Bool crossover)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiStartStrongbranch (SCIP_LPI *lpi)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiEndStrongbranch (SCIP_LPI *lpi)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiStrongbranchFrac (SCIP_LPI lpi, int col, SCIP_Real psol, int itlim, SCIP_Real down, SCIP_Real up, SCIP_Bool downvalid, SCIP_Bool upvalid, int iter)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiStrongbranchesFrac (SCIP_LPI lpi, int cols, int ncols, SCIP_Real psols, int itlim, SCIP_Real down, SCIP_Real up, SCIP_Bool downvalid, SCIP_Bool upvalid, int iter)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiStrongbranchInt (SCIP_LPI lpi, int col, SCIP_Real psol, int itlim, SCIP_Real down, SCIP_Real up, SCIP_Bool downvalid, SCIP_Bool upvalid, int iter)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiStrongbranchesInt (SCIP_LPI lpi, int cols, int ncols, SCIP_Real psols, int itlim, SCIP_Real down, SCIP_Real up, SCIP_Bool downvalid, SCIP_Bool upvalid, int iter)

Solution Information Methods
SCIP_EXPORT SCIP_Bool	SCIPlpiWasSolved (SCIP_LPI *lpi)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiGetSolFeasibility (SCIP_LPI lpi, SCIP_Bool primalfeasible, SCIP_Bool *dualfeasible)

SCIP_EXPORT SCIP_Bool	SCIPlpiExistsPrimalRay (SCIP_LPI *lpi)

SCIP_EXPORT SCIP_Bool	SCIPlpiHasPrimalRay (SCIP_LPI *lpi)

SCIP_EXPORT SCIP_Bool	SCIPlpiIsPrimalUnbounded (SCIP_LPI *lpi)

SCIP_EXPORT SCIP_Bool	SCIPlpiIsPrimalInfeasible (SCIP_LPI *lpi)

SCIP_EXPORT SCIP_Bool	SCIPlpiIsPrimalFeasible (SCIP_LPI *lpi)

SCIP_EXPORT SCIP_Bool	SCIPlpiExistsDualRay (SCIP_LPI *lpi)

SCIP_EXPORT SCIP_Bool	SCIPlpiHasDualRay (SCIP_LPI *lpi)

SCIP_EXPORT SCIP_Bool	SCIPlpiIsDualUnbounded (SCIP_LPI *lpi)

SCIP_EXPORT SCIP_Bool	SCIPlpiIsDualInfeasible (SCIP_LPI *lpi)

SCIP_EXPORT SCIP_Bool	SCIPlpiIsDualFeasible (SCIP_LPI *lpi)

SCIP_EXPORT SCIP_Bool	SCIPlpiIsOptimal (SCIP_LPI *lpi)

SCIP_EXPORT SCIP_Bool	SCIPlpiIsStable (SCIP_LPI *lpi)

SCIP_EXPORT SCIP_Bool	SCIPlpiIsObjlimExc (SCIP_LPI *lpi)

SCIP_EXPORT SCIP_Bool	SCIPlpiIsIterlimExc (SCIP_LPI *lpi)

SCIP_EXPORT SCIP_Bool	SCIPlpiIsTimelimExc (SCIP_LPI *lpi)

SCIP_EXPORT int	SCIPlpiGetInternalStatus (SCIP_LPI *lpi)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiIgnoreInstability (SCIP_LPI lpi, SCIP_Bool success)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiGetObjval (SCIP_LPI lpi, SCIP_Real objval)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiGetSol (SCIP_LPI lpi, SCIP_Real objval, SCIP_Real primsol, SCIP_Real dualsol, SCIP_Real activity, SCIP_Real redcost)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiGetPrimalRay (SCIP_LPI lpi, SCIP_Real ray)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiGetDualfarkas (SCIP_LPI lpi, SCIP_Real dualfarkas)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiGetIterations (SCIP_LPI lpi, int iterations)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiGetRealSolQuality (SCIP_LPI lpi, SCIP_LPSOLQUALITY qualityindicator, SCIP_Real quality)

LP Basis Methods
SCIP_EXPORT SCIP_RETCODE	SCIPlpiGetBase (SCIP_LPI lpi, int cstat, int *rstat)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiSetBase (SCIP_LPI lpi, const int cstat, const int *rstat)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiGetBasisInd (SCIP_LPI lpi, int bind)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiGetBInvRow (SCIP_LPI lpi, int r, SCIP_Real coef, int inds, int ninds)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiGetBInvCol (SCIP_LPI lpi, int c, SCIP_Real coef, int inds, int ninds)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiGetBInvARow (SCIP_LPI lpi, int r, const SCIP_Real binvrow, SCIP_Real coef, int inds, int *ninds)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiGetBInvACol (SCIP_LPI lpi, int c, SCIP_Real coef, int inds, int ninds)

LPi State Methods
SCIP_EXPORT SCIP_RETCODE	SCIPlpiGetState (SCIP_LPI lpi, BMS_BLKMEM blkmem, SCIP_LPISTATE **lpistate)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiSetState (SCIP_LPI lpi, BMS_BLKMEM blkmem, const SCIP_LPISTATE *lpistate)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiClearState (SCIP_LPI *lpi)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiFreeState (SCIP_LPI lpi, BMS_BLKMEM blkmem, SCIP_LPISTATE **lpistate)

SCIP_EXPORT SCIP_Bool	SCIPlpiHasStateBasis (SCIP_LPI lpi, SCIP_LPISTATE lpistate)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiReadState (SCIP_LPI lpi, const char fname)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiWriteState (SCIP_LPI lpi, const char fname)

LPi Pricing Norms Methods
SCIP_RETCODE	SCIPlpiGetNorms (SCIP_LPI lpi, BMS_BLKMEM blkmem, SCIP_LPINORMS **lpinorms)

SCIP_RETCODE	SCIPlpiSetNorms (SCIP_LPI lpi, BMS_BLKMEM blkmem, const SCIP_LPINORMS *lpinorms)

SCIP_RETCODE	SCIPlpiFreeNorms (SCIP_LPI lpi, BMS_BLKMEM blkmem, SCIP_LPINORMS **lpinorms)

Parameter Methods
SCIP_EXPORT SCIP_RETCODE	SCIPlpiGetIntpar (SCIP_LPI lpi, SCIP_LPPARAM type, int ival)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiSetIntpar (SCIP_LPI *lpi, SCIP_LPPARAM type, int ival)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiGetRealpar (SCIP_LPI lpi, SCIP_LPPARAM type, SCIP_Real dval)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiSetRealpar (SCIP_LPI *lpi, SCIP_LPPARAM type, SCIP_Real dval)

Numerical Methods
SCIP_EXPORT SCIP_Real	SCIPlpiInfinity (SCIP_LPI *lpi)

SCIP_EXPORT SCIP_Bool	SCIPlpiIsInfinity (SCIP_LPI *lpi, SCIP_Real val)

File Interface Methods
SCIP_EXPORT SCIP_RETCODE	SCIPlpiReadLP (SCIP_LPI lpi, const char fname)

SCIP_EXPORT SCIP_RETCODE	SCIPlpiWriteLP (SCIP_LPI lpi, const char fname)

Function Documentation

◆ SCIPlpiGetSolverName()

SCIP_EXPORT const char* SCIPlpiGetSolverName ( void )

gets name and version of LP solver

Referenced by doScipCreate(), lpFlushChgCols(), lpFlushChgRows(), SCIPlpCreate(), SCIPlpMarkFlushed(), and SCIPprintVersion().

◆ SCIPlpiGetSolverDesc()

SCIP_EXPORT const char* SCIPlpiGetSolverDesc ( void )

gets description of LP solver (developer, webpage, ...)

Referenced by doScipCreate().

◆ SCIPlpiGetSolverPointer()

SCIP_EXPORT void* SCIPlpiGetSolverPointer ( SCIP_LPI * lpi )

gets pointer for LP solver - use only with great care

The behavior of this function depends on the solver and its use is therefore only recommended if you really know what you are doing. In general, it returns a pointer to the LP solver object.

Parameters

lpi	pointer to an LP interface structure

◆ SCIPlpiSetIntegralityInformation()

SCIP_EXPORT SCIP_RETCODE SCIPlpiSetIntegralityInformation	(	SCIP_LPI *	lpi,
		int	ncols,
		int *	intInfo
	)

pass integrality information about variables to the solver

Parameters

lpi	pointer to an LP interface structure
ncols	length of integrality array
intInfo	integrality array (0: continuous, 1: integer). May be NULL iff ncols is 0.

Referenced by lpCopyIntegrality().

◆ SCIPlpiHasPrimalSolve()

SCIP_EXPORT SCIP_Bool SCIPlpiHasPrimalSolve ( void )

informs about availability of a primal simplex solving method

◆ SCIPlpiHasDualSolve()

SCIP_EXPORT SCIP_Bool SCIPlpiHasDualSolve ( void )

informs about availability of a dual simplex solving method

◆ SCIPlpiHasBarrierSolve()

SCIP_EXPORT SCIP_Bool SCIPlpiHasBarrierSolve ( void )

informs about availability of a barrier solving method

◆ SCIPlpiCreate()

SCIP_EXPORT SCIP_RETCODE SCIPlpiCreate	(	SCIP_LPI **	lpi,
		SCIP_MESSAGEHDLR *	messagehdlr,
		const char *	name,
		SCIP_OBJSEN	objsen
	)

creates an LP problem object

Parameters

lpi	pointer to an LP interface structure
messagehdlr	message handler to use for printing messages, or NULL
name	problem name
objsen	objective sense

Referenced by addConcaveEstimatorMultivariate(), createLP(), initAlternativeLP(), polyscip::Polyscip::printResults(), SCIP_DECL_PARAMCHGD(), SCIPlpComputeRelIntPoint(), SCIPlpCreate(), solveClassification(), and solveMinIISC().

◆ SCIPlpiFree()

SCIP_EXPORT SCIP_RETCODE SCIPlpiFree ( SCIP_LPI ** lpi )

deletes an LP problem object

Parameters

lpi	pointer to an LP interface structure

Referenced by createLP(), polyscip::Polyscip::printResults(), SCIP_DECL_CONSEXITSOL(), SCIP_DECL_PARAMCHGD(), SCIPlpComputeRelIntPoint(), SCIPlpFree(), sepadataFree(), solveClassification(), and solveMinIISC().

◆ SCIPlpiLoadColLP()

SCIP_EXPORT SCIP_RETCODE SCIPlpiLoadColLP	(	SCIP_LPI *	lpi,
		SCIP_OBJSEN	objsen,
		int	ncols,
		const SCIP_Real *	obj,
		const SCIP_Real *	lb,
		const SCIP_Real *	ub,
		char **	colnames,
		int	nrows,
		const SCIP_Real *	lhs,
		const SCIP_Real *	rhs,
		char **	rownames,
		int	nnonz,
		const int *	beg,
		const int *	ind,
		const SCIP_Real *	val
	)

copies LP data with column matrix into LP solver

Parameters

lpi	LP interface structure
objsen	objective sense
ncols	number of columns
obj	objective function values of columns
lb	lower bounds of columns
ub	upper bounds of columns
colnames	column names, or NULL
nrows	number of rows
lhs	left hand sides of rows
rhs	right hand sides of rows
rownames	row names, or NULL
nnonz	number of nonzero elements in the constraint matrix
beg	start index of each column in ind- and val-array
ind	row indices of constraint matrix entries
val	values of constraint matrix entries

Referenced by polyscip::Polyscip::printResults().

◆ SCIPlpiAddCols()

SCIP_EXPORT SCIP_RETCODE SCIPlpiAddCols	(	SCIP_LPI *	lpi,
		int	ncols,
		const SCIP_Real *	obj,
		const SCIP_Real *	lb,
		const SCIP_Real *	ub,
		char **	colnames,
		int	nnonz,
		const int *	beg,
		const int *	ind,
		const SCIP_Real *	val
	)

adds columns to the LP

Note: ind array is not checked for duplicates, problems may appear if indices are added more than once

Parameters

lpi	LP interface structure
ncols	number of columns to be added
obj	objective function values of new columns
lb	lower bounds of new columns
ub	upper bounds of new columns
colnames	column names, or NULL
nnonz	number of nonzero elements to be added to the constraint matrix
beg	start index of each column in ind- and val-array, or NULL if nnonz == 0
ind	row indices of constraint matrix entries, or NULL if nnonz == 0
val	values of constraint matrix entries, or NULL if nnonz == 0

Referenced by addAltLPColumn(), computeRelIntPoint(), createAltLPColumn(), createLP(), lpFlushAddCols(), SCIP_DECL_PARAMCHGD(), solveClassification(), and solveMinIISC().

◆ SCIPlpiDelCols()

SCIP_EXPORT SCIP_RETCODE SCIPlpiDelCols	(	SCIP_LPI *	lpi,
		int	firstcol,
		int	lastcol
	)

deletes all columns in the given range from LP

Parameters

lpi	LP interface structure
firstcol	first column to be deleted
lastcol	last column to be deleted

Referenced by lpFlushDelCols().

◆ SCIPlpiDelColset()

SCIP_EXPORT SCIP_RETCODE SCIPlpiDelColset	(	SCIP_LPI *	lpi,
		int *	dstat
	)

deletes columns from SCIP_LPI; the new position of a column must not be greater that its old position

Parameters

lpi	LP interface structure
dstat	deletion status of columns input: 1 if column should be deleted, 0 if not output: new position of column, -1 if column was deleted

Referenced by lpDelColset().

◆ SCIPlpiAddRows()

SCIP_EXPORT SCIP_RETCODE SCIPlpiAddRows	(	SCIP_LPI *	lpi,
		int	nrows,
		const SCIP_Real *	lhs,
		const SCIP_Real *	rhs,
		char **	rownames,
		int	nnonz,
		const int *	beg,
		const int *	ind,
		const SCIP_Real *	val
	)

adds rows to the LP

Note: ind array is not checked for duplicates, problems may appear if indices are added more than once

Parameters

lpi	LP interface structure
nrows	number of rows to be added
lhs	left hand sides of new rows
rhs	right hand sides of new rows
rownames	row names, or NULL
nnonz	number of nonzero elements to be added to the constraint matrix
beg	start index of each row in ind- and val-array, or NULL if nnonz == 0
ind	column indices of constraint matrix entries, or NULL if nnonz == 0
val	values of constraint matrix entries, or NULL if nnonz == 0

Referenced by addAltLPColumn(), computeRelIntPoint(), createLP(), initAlternativeLP(), lpFlushAddRows(), SCIP_DECL_PARAMCHGD(), solveClassification(), and solveMinIISC().

◆ SCIPlpiDelRows()

SCIP_EXPORT SCIP_RETCODE SCIPlpiDelRows	(	SCIP_LPI *	lpi,
		int	firstrow,
		int	lastrow
	)

deletes all rows in the given range from LP

Parameters

lpi	LP interface structure
firstrow	first row to be deleted
lastrow	last row to be deleted

Referenced by lpFlushDelRows().

◆ SCIPlpiDelRowset()

SCIP_EXPORT SCIP_RETCODE SCIPlpiDelRowset	(	SCIP_LPI *	lpi,
		int *	dstat
	)

deletes rows from SCIP_LPI; the new position of a row must not be greater that its old position

Parameters

lpi	LP interface structure
dstat	deletion status of rows input: 1 if row should be deleted, 0 if not output: new position of row, -1 if row was deleted

Referenced by lpDelRowset().

◆ SCIPlpiClear()

SCIP_EXPORT SCIP_RETCODE SCIPlpiClear ( SCIP_LPI * lpi )

clears the whole LP

Parameters

lpi	LP interface structure

◆ SCIPlpiChgBounds()

SCIP_EXPORT SCIP_RETCODE SCIPlpiChgBounds	(	SCIP_LPI *	lpi,
		int	ncols,
		const int *	ind,
		const SCIP_Real *	lb,
		const SCIP_Real *	ub
	)

changes lower and upper bounds of columns

Parameters

lpi	LP interface structure
ncols	number of columns to change bounds for
ind	column indices or NULL if ncols is zero
lb	values for the new lower bounds or NULL if ncols is zero
ub	values for the new upper bounds or NULL if ncols is zero

Referenced by fixAltLPVariable(), fixAltLPVariables(), lpFlushChgCols(), lpLexDualSimplex(), runBoundHeuristic(), SCIPcomputeConvexEnvelopeFacet(), SCIPconflictAnalyzeStrongbranch(), unfixAltLPVariable(), and unfixAltLPVariables().

◆ SCIPlpiChgSides()

SCIP_EXPORT SCIP_RETCODE SCIPlpiChgSides	(	SCIP_LPI *	lpi,
		int	nrows,
		const int *	ind,
		const SCIP_Real *	lhs,
		const SCIP_Real *	rhs
	)

changes left and right hand sides of rows

Parameters

lpi	LP interface structure
nrows	number of rows to change sides for
ind	row indices
lhs	new values for left hand sides
rhs	new values for right hand sides

Referenced by lpFlushChgRows(), lpLexDualSimplex(), runBoundHeuristic(), scaleFirstRow(), and SCIPcomputeConvexEnvelopeFacet().

◆ SCIPlpiChgCoef()

SCIP_EXPORT SCIP_RETCODE SCIPlpiChgCoef	(	SCIP_LPI *	lpi,
		int	row,
		int	col,
		SCIP_Real	newval
	)

changes a single coefficient

Parameters

lpi	LP interface structure
row	row number of coefficient to change
col	column number of coefficient to change
newval	new value of coefficient

Referenced by updateFirstRow(), updateFirstRowGlobal(), and updateObjUpperbound().

◆ SCIPlpiChgObjsen()

SCIP_EXPORT SCIP_RETCODE SCIPlpiChgObjsen	(	SCIP_LPI *	lpi,
		SCIP_OBJSEN	objsen
	)

changes the objective sense

Parameters

lpi	LP interface structure
objsen	new objective sense

◆ SCIPlpiChgObj()

SCIP_EXPORT SCIP_RETCODE SCIPlpiChgObj	(	SCIP_LPI *	lpi,
		int	ncols,
		const int *	ind,
		const SCIP_Real *	obj
	)

changes objective values of columns in the LP

Parameters

lpi	LP interface structure
ncols	number of columns to change objective value for
ind	column indices to change objective value for
obj	new objective values for columns

Referenced by lpFlushChgCols(), lpLexDualSimplex(), SCIPcomputeConvexEnvelopeFacet(), setAltLPObj(), and setAltLPObjZero().

◆ SCIPlpiScaleRow()

SCIP_EXPORT SCIP_RETCODE SCIPlpiScaleRow	(	SCIP_LPI *	lpi,
		int	row,
		SCIP_Real	scaleval
	)

multiplies a row with a non-zero scalar; for negative scalars, the row's sense is switched accordingly

Parameters

lpi	LP interface structure
row	row number to scale
scaleval	scaling multiplier

◆ SCIPlpiScaleCol()

SCIP_EXPORT SCIP_RETCODE SCIPlpiScaleCol	(	SCIP_LPI *	lpi,
		int	col,
		SCIP_Real	scaleval
	)

multiplies a column with a non-zero scalar; the objective value is multiplied with the scalar, and the bounds are divided by the scalar; for negative scalars, the column's bounds are switched

Parameters

lpi	LP interface structure
col	column number to scale
scaleval	scaling multiplier

◆ SCIPlpiGetNRows()

SCIP_EXPORT SCIP_RETCODE SCIPlpiGetNRows	(	SCIP_LPI *	lpi,
		int *	nrows
	)

gets the number of rows in the LP

Parameters

lpi	LP interface structure
nrows	pointer to store the number of rows

Referenced by addAltLPColumn(), SCIPcomputeConvexEnvelopeFacet(), SCIPlpFlush(), solveClassification(), and solveMinIISC().

◆ SCIPlpiGetNCols()

SCIP_EXPORT SCIP_RETCODE SCIPlpiGetNCols	(	SCIP_LPI *	lpi,
		int *	ncols
	)

gets the number of columns in the LP

Parameters

lpi	LP interface structure
ncols	pointer to store the number of cols

Referenced by addAltLPColumn(), BENDERS_CUTORACLE(), checkIISlocal(), checkLPBoundsClean(), computeRelIntPoint(), extendToCover(), scaleFirstRow(), SCIPcomputeConvexEnvelopeFacet(), SCIPlpFlush(), solveClassification(), and solveMinIISC().

◆ SCIPlpiGetObjsen()

SCIP_EXPORT SCIP_RETCODE SCIPlpiGetObjsen	(	SCIP_LPI *	lpi,
		SCIP_OBJSEN *	objsen
	)

gets the objective sense of the LP

Parameters

lpi	LP interface structure
objsen	pointer to store objective sense

◆ SCIPlpiGetNNonz()

SCIP_EXPORT SCIP_RETCODE SCIPlpiGetNNonz	(	SCIP_LPI *	lpi,
		int *	nnonz
	)

gets the number of nonzero elements in the LP constraint matrix

Parameters

lpi	LP interface structure
nnonz	pointer to store the number of nonzeros

◆ SCIPlpiGetCols()

SCIP_EXPORT SCIP_RETCODE SCIPlpiGetCols	(	SCIP_LPI *	lpi,
		int	firstcol,
		int	lastcol,
		SCIP_Real *	lb,
		SCIP_Real *	ub,
		int *	nnonz,
		int *	beg,
		int *	ind,
		SCIP_Real *	val
	)

gets columns from LP problem object; the arrays have to be large enough to store all values; Either both, lb and ub, have to be NULL, or both have to be non-NULL, either nnonz, beg, ind, and val have to be NULL, or all of them have to be non-NULL.

Parameters

lpi	LP interface structure
firstcol	first column to get from LP
lastcol	last column to get from LP
lb	buffer to store the lower bound vector, or NULL
ub	buffer to store the upper bound vector, or NULL
nnonz	pointer to store the number of nonzero elements returned, or NULL
beg	buffer to store start index of each column in ind- and val-array, or NULL
ind	buffer to store row indices of constraint matrix entries, or NULL
val	buffer to store values of constraint matrix entries, or NULL

◆ SCIPlpiGetRows()

SCIP_EXPORT SCIP_RETCODE SCIPlpiGetRows	(	SCIP_LPI *	lpi,
		int	firstrow,
		int	lastrow,
		SCIP_Real *	lhs,
		SCIP_Real *	rhs,
		int *	nnonz,
		int *	beg,
		int *	ind,
		SCIP_Real *	val
	)

gets rows from LP problem object; the arrays have to be large enough to store all values. Either both, lhs and rhs, have to be NULL, or both have to be non-NULL, either nnonz, beg, ind, and val have to be NULL, or all of them have to be non-NULL.

Parameters

lpi	LP interface structure
firstrow	first row to get from LP
lastrow	last row to get from LP
lhs	buffer to store left hand side vector, or NULL
rhs	buffer to store right hand side vector, or NULL
nnonz	pointer to store the number of nonzero elements returned, or NULL
beg	buffer to store start index of each row in ind- and val-array, or NULL
ind	buffer to store column indices of constraint matrix entries, or NULL
val	buffer to store values of constraint matrix entries, or NULL

Referenced by scaleFirstRow().

◆ SCIPlpiGetColNames()

SCIP_EXPORT SCIP_RETCODE SCIPlpiGetColNames	(	SCIP_LPI *	lpi,
		int	firstcol,
		int	lastcol,
		char **	colnames,
		char *	namestorage,
		int	namestoragesize,
		int *	storageleft
	)

gets column names

Parameters

lpi	LP interface structure
firstcol	first column to get name from LP
lastcol	last column to get name from LP
colnames	pointers to column names (of size at least lastcol-firstcol+1) or NULL if namestoragesize is zero
namestorage	storage for col names or NULL if namestoragesize is zero
namestoragesize	size of namestorage (if 0, -storageleft returns the storage needed)
storageleft	amount of storage left (if < 0 the namestorage was not big enough) or NULL if namestoragesize is zero

◆ SCIPlpiGetRowNames()

SCIP_EXPORT SCIP_RETCODE SCIPlpiGetRowNames	(	SCIP_LPI *	lpi,
		int	firstrow,
		int	lastrow,
		char **	rownames,
		char *	namestorage,
		int	namestoragesize,
		int *	storageleft
	)

gets row names

Parameters

lpi	LP interface structure
firstrow	first row to get name from LP
lastrow	last row to get name from LP
rownames	pointers to row names (of size at least lastrow-firstrow+1) or NULL if namestoragesize is zero
namestorage	storage for row names or NULL if namestoragesize is zero
namestoragesize	size of namestorage (if 0, -storageleft returns the storage needed)
storageleft	amount of storage left (if < 0 the namestorage was not big enough) or NULL if namestoragesize is zero

◆ SCIPlpiGetObj()

SCIP_EXPORT SCIP_RETCODE SCIPlpiGetObj	(	SCIP_LPI *	lpi,
		int	firstcol,
		int	lastcol,
		SCIP_Real *	vals
	)

gets objective coefficients from LP problem object

Parameters

lpi	LP interface structure
firstcol	first column to get objective coefficient for
lastcol	last column to get objective coefficient for
vals	array to store objective coefficients

Referenced by lpFlushChgCols(), lpLexDualSimplex(), and SCIPlpMarkFlushed().

◆ SCIPlpiGetBounds()

SCIP_EXPORT SCIP_RETCODE SCIPlpiGetBounds	(	SCIP_LPI *	lpi,
		int	firstcol,
		int	lastcol,
		SCIP_Real *	lbs,
		SCIP_Real *	ubs
	)

gets current bounds from LP problem object

Parameters

lpi	LP interface structure
firstcol	first column to get bounds for
lastcol	last column to get bounds for
lbs	array to store lower bound values, or NULL
ubs	array to store upper bound values, or NULL

Referenced by checkLPBoundsClean(), lpFlushChgCols(), lpLexDualSimplex(), and SCIPlpMarkFlushed().

◆ SCIPlpiGetSides()

SCIP_EXPORT SCIP_RETCODE SCIPlpiGetSides	(	SCIP_LPI *	lpi,
		int	firstrow,
		int	lastrow,
		SCIP_Real *	lhss,
		SCIP_Real *	rhss
	)

gets current row sides from LP problem object

Parameters

lpi	LP interface structure
firstrow	first row to get sides for
lastrow	last row to get sides for
lhss	array to store left hand side values, or NULL
rhss	array to store right hand side values, or NULL

Referenced by getFarkasProof(), lpFlushChgRows(), lpLexDualSimplex(), and SCIPlpMarkFlushed().

◆ SCIPlpiGetCoef()

SCIP_EXPORT SCIP_RETCODE SCIPlpiGetCoef	(	SCIP_LPI *	lpi,
		int	row,
		int	col,
		SCIP_Real *	val
	)

gets a single coefficient

Parameters

lpi	LP interface structure
row	row number of coefficient
col	column number of coefficient
val	pointer to store the value of the coefficient

Referenced by SCIPdummyDebugMethodForSun(), and updateObjUpperbound().

◆ SCIPlpiSolvePrimal()

SCIP_EXPORT SCIP_RETCODE SCIPlpiSolvePrimal ( SCIP_LPI * lpi )

calls primal simplex to solve the LP

Parameters

lpi	LP interface structure

Referenced by checkAltLPInfeasible(), lpLexDualSimplex(), lpPrimalSimplex(), polyscip::Polyscip::printResults(), SCIP_DECL_PARAMCHGD(), and SCIPcomputeConvexEnvelopeFacet().

◆ SCIPlpiSolveDual()

SCIP_EXPORT SCIP_RETCODE SCIPlpiSolveDual ( SCIP_LPI * lpi )

calls dual simplex to solve the LP

Parameters

lpi	LP interface structure

Referenced by checkAltLPInfeasible(), computeRelIntPoint(), conflictAnalyzeLP(), lpDualSimplex(), lpLexDualSimplex(), runBoundHeuristic(), SCIPcomputeConvexEnvelopeFacet(), and SCIPconflictAnalyzeStrongbranch().

◆ SCIPlpiSolveBarrier()

SCIP_EXPORT SCIP_RETCODE SCIPlpiSolveBarrier	(	SCIP_LPI *	lpi,
		SCIP_Bool	crossover
	)

calls barrier or interior point algorithm to solve the LP with crossover to simplex basis

Parameters

lpi	LP interface structure
crossover	perform crossover

Referenced by lpBarrier().

◆ SCIPlpiStartStrongbranch()

SCIP_EXPORT SCIP_RETCODE SCIPlpiStartStrongbranch ( SCIP_LPI * lpi )

start strong branching - call before any strong branching

Parameters

lpi	LP interface structure

Referenced by SCIPconflictAnalyzeStrongbranch(), and SCIPlpStartStrongbranch().

◆ SCIPlpiEndStrongbranch()

SCIP_EXPORT SCIP_RETCODE SCIPlpiEndStrongbranch ( SCIP_LPI * lpi )

end strong branching - call after any strong branching

Parameters

lpi	LP interface structure

Referenced by SCIPconflictAnalyzeStrongbranch(), and SCIPlpEndStrongbranch().

◆ SCIPlpiStrongbranchFrac()

SCIP_EXPORT SCIP_RETCODE SCIPlpiStrongbranchFrac	(	SCIP_LPI *	lpi,
		int	col,
		SCIP_Real	psol,
		int	itlim,
		SCIP_Real *	down,
		SCIP_Real *	up,
		SCIP_Bool *	downvalid,
		SCIP_Bool *	upvalid,
		int *	iter
	)

performs strong branching iterations on one fractional candidate

Parameters

lpi	LP interface structure
col	column to apply strong branching on
psol	fractional current primal solution value of column
itlim	iteration limit for strong branchings
down	stores dual bound after branching column down
up	stores dual bound after branching column up
downvalid	stores whether the returned down value is a valid dual bound; otherwise, it can only be used as an estimate value
upvalid	stores whether the returned up value is a valid dual bound; otherwise, it can only be used as an estimate value
iter	stores total number of strong branching iterations, or -1; may be NULL

Referenced by SCIPcolGetStrongbranch().

◆ SCIPlpiStrongbranchesFrac()

SCIP_EXPORT SCIP_RETCODE SCIPlpiStrongbranchesFrac	(	SCIP_LPI *	lpi,
		int *	cols,
		int	ncols,
		SCIP_Real *	psols,
		int	itlim,
		SCIP_Real *	down,
		SCIP_Real *	up,
		SCIP_Bool *	downvalid,
		SCIP_Bool *	upvalid,
		int *	iter
	)

performs strong branching iterations on given fractional candidates

Parameters

lpi	LP interface structure
cols	columns to apply strong branching on
ncols	number of columns
psols	fractional current primal solution values of columns
itlim	iteration limit for strong branchings
down	stores dual bounds after branching columns down
up	stores dual bounds after branching columns up
downvalid	stores whether the returned down values are valid dual bounds; otherwise, they can only be used as an estimate values
upvalid	stores whether the returned up values are a valid dual bounds; otherwise, they can only be used as an estimate values
iter	stores total number of strong branching iterations, or -1; may be NULL

Referenced by SCIPcolGetStrongbranches().

◆ SCIPlpiStrongbranchInt()

SCIP_EXPORT SCIP_RETCODE SCIPlpiStrongbranchInt	(	SCIP_LPI *	lpi,
		int	col,
		SCIP_Real	psol,
		int	itlim,
		SCIP_Real *	down,
		SCIP_Real *	up,
		SCIP_Bool *	downvalid,
		SCIP_Bool *	upvalid,
		int *	iter
	)

performs strong branching iterations on one candidate with integral value

Parameters

lpi	LP interface structure
col	column to apply strong branching on
psol	current integral primal solution value of column
itlim	iteration limit for strong branchings
down	stores dual bound after branching column down
up	stores dual bound after branching column up
downvalid	stores whether the returned down value is a valid dual bound; otherwise, it can only be used as an estimate value
upvalid	stores whether the returned up value is a valid dual bound; otherwise, it can only be used as an estimate value
iter	stores total number of strong branching iterations, or -1; may be NULL

Referenced by SCIPcolGetStrongbranch().

◆ SCIPlpiStrongbranchesInt()

SCIP_EXPORT SCIP_RETCODE SCIPlpiStrongbranchesInt	(	SCIP_LPI *	lpi,
		int *	cols,
		int	ncols,
		SCIP_Real *	psols,
		int	itlim,
		SCIP_Real *	down,
		SCIP_Real *	up,
		SCIP_Bool *	downvalid,
		SCIP_Bool *	upvalid,
		int *	iter
	)

performs strong branching iterations on given candidates with integral values

Parameters

lpi	LP interface structure
cols	columns to apply strong branching on
ncols	number of columns
psols	current integral primal solution values of columns
itlim	iteration limit for strong branchings
down	stores dual bounds after branching columns down
up	stores dual bounds after branching columns up
downvalid	stores whether the returned down values are valid dual bounds; otherwise, they can only be used as an estimate values
upvalid	stores whether the returned up values are a valid dual bounds; otherwise, they can only be used as an estimate values
iter	stores total number of strong branching iterations, or -1; may be NULL

Referenced by SCIPcolGetStrongbranches().

◆ SCIPlpiWasSolved()

SCIP_EXPORT SCIP_Bool SCIPlpiWasSolved ( SCIP_LPI * lpi )

returns whether a solve method was called after the last modification of the LP

Parameters

lpi	LP interface structure

Referenced by performStrongbranchWithPropagation(), and SCIPconflictAnalyzeLP().

◆ SCIPlpiGetSolFeasibility()

SCIP_EXPORT SCIP_RETCODE SCIPlpiGetSolFeasibility	(	SCIP_LPI *	lpi,
		SCIP_Bool *	primalfeasible,
		SCIP_Bool *	dualfeasible
	)

gets information about primal and dual feasibility of the current LP solution

The feasibility information is with respect to the last solving call and it is only relevant if SCIPlpiWasSolved() returns true. If the LP is changed, this information might be invalidated.

Note that primalfeasible and dualfeasible should only return true if the solver has proved the respective LP to be feasible. Thus, the return values should be equal to the values of SCIPlpiIsPrimalFeasible() and SCIPlpiIsDualFeasible(), respectively. Note that if feasibility cannot be proved, they should return false (even if the problem might actually be feasible).

Parameters

lpi	LP interface structure
primalfeasible	pointer to store primal feasibility status
dualfeasible	pointer to store dual feasibility status

Referenced by lpAlgorithm().

◆ SCIPlpiExistsPrimalRay()

SCIP_EXPORT SCIP_Bool SCIPlpiExistsPrimalRay ( SCIP_LPI * lpi )

returns TRUE iff LP is proven to have a primal unbounded ray (but not necessary a primal feasible point); this does not necessarily mean, that the solver knows and can return the primal ray

Parameters

lpi	LP interface structure

Referenced by checkAltLPInfeasible(), and lpSolve().

◆ SCIPlpiHasPrimalRay()

SCIP_EXPORT SCIP_Bool SCIPlpiHasPrimalRay ( SCIP_LPI * lpi )

returns TRUE iff LP is proven to have a primal unbounded ray (but not necessary a primal feasible point), and the solver knows and can return the primal ray

Parameters

lpi	LP interface structure

Referenced by SCIPlpGetPrimalRay(), and SCIPlpGetUnboundedSol().

◆ SCIPlpiIsPrimalUnbounded()

SCIP_EXPORT SCIP_Bool SCIPlpiIsPrimalUnbounded ( SCIP_LPI * lpi )

returns TRUE iff LP is proven to be primal unbounded

Parameters

lpi	LP interface structure

Referenced by checkAltLPInfeasible(), and lpSolve().

◆ SCIPlpiIsPrimalInfeasible()

SCIP_EXPORT SCIP_Bool SCIPlpiIsPrimalInfeasible ( SCIP_LPI * lpi )

returns TRUE iff LP is proven to be primal infeasible

Parameters

lpi	LP interface structure

Referenced by checkAltLPInfeasible(), conflictAnalyzeLP(), getFarkasProof(), lpSolve(), polyscip::Polyscip::printResults(), runBoundHeuristic(), SCIP_DECL_PARAMCHGD(), and SCIPconflictAnalyzeLP().

◆ SCIPlpiIsPrimalFeasible()

SCIP_EXPORT SCIP_Bool SCIPlpiIsPrimalFeasible ( SCIP_LPI * lpi )

returns TRUE iff LP is proven to be primal feasible

Parameters

lpi	LP interface structure

Referenced by lpSolve(), and polyscip::Polyscip::printResults().

◆ SCIPlpiExistsDualRay()

SCIP_EXPORT SCIP_Bool SCIPlpiExistsDualRay ( SCIP_LPI * lpi )

returns TRUE iff LP is proven to have a dual unbounded ray (but not necessary a dual feasible point); this does not necessarily mean, that the solver knows and can return the dual ray

Parameters

lpi	LP interface structure

◆ SCIPlpiHasDualRay()

SCIP_EXPORT SCIP_Bool SCIPlpiHasDualRay ( SCIP_LPI * lpi )

returns TRUE iff LP is proven to have a dual unbounded ray (but not necessary a dual feasible point), and the solver knows and can return the dual ray

Parameters

lpi	LP interface structure

Referenced by getFarkasProof(), lpSolve(), and SCIPlpSolveAndEval().

◆ SCIPlpiIsDualUnbounded()

SCIP_EXPORT SCIP_Bool SCIPlpiIsDualUnbounded ( SCIP_LPI * lpi )

returns TRUE iff LP is proven to be dual unbounded

Parameters

lpi	LP interface structure

◆ SCIPlpiIsDualInfeasible()

SCIP_EXPORT SCIP_Bool SCIPlpiIsDualInfeasible ( SCIP_LPI * lpi )

returns TRUE iff LP is proven to be dual infeasible

Parameters

lpi	LP interface structure

◆ SCIPlpiIsDualFeasible()

SCIP_EXPORT SCIP_Bool SCIPlpiIsDualFeasible ( SCIP_LPI * lpi )

returns TRUE iff LP is proven to be dual feasible

Parameters

lpi	LP interface structure

Referenced by conflictAnalyzeLP(), getFarkasProof(), lpSolve(), performStrongbranchWithPropagation(), and runBoundHeuristic().

◆ SCIPlpiIsOptimal()

SCIP_EXPORT SCIP_Bool SCIPlpiIsOptimal ( SCIP_LPI * lpi )

returns TRUE iff LP was solved to optimality

Parameters

lpi	LP interface structure

Referenced by checkAltLPInfeasible(), computeRelIntPoint(), conflictAnalyzeLP(), lpLexDualSimplex(), and lpSolve().

◆ SCIPlpiIsStable()

SCIP_EXPORT SCIP_Bool SCIPlpiIsStable ( SCIP_LPI * lpi )

returns TRUE iff current LP solution is stable

This function should return true if the solution is reliable, i.e., feasible and optimal (or proven infeasible/unbounded) with respect to the original problem. The optimality status might be with respect to a scaled version of the problem, but the solution might not be feasible to the unscaled original problem; in this case, SCIPlpiIsStable() should return false.

Parameters

lpi	LP interface structure

Referenced by checkAltLPInfeasible(), and lpSolveStable().

◆ SCIPlpiIsObjlimExc()

SCIP_EXPORT SCIP_Bool SCIPlpiIsObjlimExc ( SCIP_LPI * lpi )

returns TRUE iff the objective limit was reached

Parameters

lpi	LP interface structure

Referenced by conflictAnalyzeLP(), getFarkasProof(), lpSolve(), runBoundHeuristic(), and SCIPlpSolveAndEval().

◆ SCIPlpiIsIterlimExc()

SCIP_EXPORT SCIP_Bool SCIPlpiIsIterlimExc ( SCIP_LPI * lpi )

returns TRUE iff the iteration limit was reached

Parameters

lpi	LP interface structure

Referenced by computeRelIntPoint(), lpSolve(), and lpSolveStable().

◆ SCIPlpiIsTimelimExc()

SCIP_EXPORT SCIP_Bool SCIPlpiIsTimelimExc ( SCIP_LPI * lpi )

returns TRUE iff the time limit was reached

Parameters

lpi	LP interface structure

Referenced by computeRelIntPoint(), and lpSolve().

◆ SCIPlpiGetInternalStatus()

SCIP_EXPORT int SCIPlpiGetInternalStatus ( SCIP_LPI * lpi )

returns the internal solution status of the solver

Parameters

lpi	LP interface structure

Referenced by checkAltLPInfeasible(), and lpSolve().

◆ SCIPlpiIgnoreInstability()

SCIP_EXPORT SCIP_RETCODE SCIPlpiIgnoreInstability	(	SCIP_LPI *	lpi,
		SCIP_Bool *	success
	)

tries to reset the internal status of the LP solver in order to ignore an instability of the last solving call

Parameters

lpi	LP interface structure
success	pointer to store, whether the instability could be ignored

Referenced by ignoreInstability().

◆ SCIPlpiGetObjval()

SCIP_EXPORT SCIP_RETCODE SCIPlpiGetObjval	(	SCIP_LPI *	lpi,
		SCIP_Real *	objval
	)

gets objective value of solution

Parameters

lpi	LP interface structure
objval	stores the objective value

Referenced by conflictAnalyzeLP(), getDualProof(), lpSolve(), performStrongbranchWithPropagation(), runBoundHeuristic(), and SCIPlpSolveAndEval().

◆ SCIPlpiGetSol()

SCIP_EXPORT SCIP_RETCODE SCIPlpiGetSol	(	SCIP_LPI *	lpi,
		SCIP_Real *	objval,
		SCIP_Real *	primsol,
		SCIP_Real *	dualsol,
		SCIP_Real *	activity,
		SCIP_Real *	redcost
	)

gets primal and dual solution vectors for feasible LPs

Before calling this function, the caller must ensure that the LP has been solved to optimality, i.e., that SCIPlpiIsOptimal() returns true.

Parameters

lpi	LP interface structure
objval	stores the objective value, may be NULL if not needed
primsol	primal solution vector, may be NULL if not needed
dualsol	dual solution vector, may be NULL if not needed
activity	row activity vector, may be NULL if not needed
redcost	reduced cost vector, may be NULL if not needed

Referenced by BENDERS_CUTORACLE(), computeRelIntPoint(), extendToCover(), getDualProof(), lpLexDualSimplex(), SCIPcomputeConvexEnvelopeFacet(), SCIPlpGetSol(), and SCIPlpGetUnboundedSol().

◆ SCIPlpiGetPrimalRay()

SCIP_EXPORT SCIP_RETCODE SCIPlpiGetPrimalRay	(	SCIP_LPI *	lpi,
		SCIP_Real *	ray
	)

gets primal ray for unbounded LPs

Parameters

lpi	LP interface structure
ray	primal ray

Referenced by SCIPlpGetPrimalRay(), and SCIPlpGetUnboundedSol().

◆ SCIPlpiGetDualfarkas()

SCIP_EXPORT SCIP_RETCODE SCIPlpiGetDualfarkas	(	SCIP_LPI *	lpi,
		SCIP_Real *	dualfarkas
	)

gets dual Farkas proof for infeasibility

Parameters

lpi	LP interface structure
dualfarkas	dual Farkas row multipliers

Referenced by getFarkasProof(), and SCIPlpGetDualfarkas().

◆ SCIPlpiGetIterations()

SCIP_EXPORT SCIP_RETCODE SCIPlpiGetIterations	(	SCIP_LPI *	lpi,
		int *	iterations
	)

gets the number of LP iterations of the last solve call

Parameters

lpi	LP interface structure
iterations	pointer to store the number of iterations of the last solve call

Referenced by conflictAnalyzeLP(), runBoundHeuristic(), SCIPconflictAnalyzeStrongbranch(), and SCIPlpGetIterations().

◆ SCIPlpiGetRealSolQuality()

SCIP_EXPORT SCIP_RETCODE SCIPlpiGetRealSolQuality	(	SCIP_LPI *	lpi,
		SCIP_LPSOLQUALITY	qualityindicator,
		SCIP_Real *	quality
	)

gets information about the quality of an LP solution

Such information is usually only available, if also a (maybe not optimal) solution is available. The LPI should return SCIP_INVALID for quality, if the requested quantity is not available.

Parameters

lpi	LP interface structure
qualityindicator	indicates which quality should be returned
quality	pointer to store quality number

Referenced by checkAltLPInfeasible(), SCIP_DECL_DISPOUTPUT(), and SCIPprintLPSolutionQuality().

◆ SCIPlpiGetBase()

SCIP_EXPORT SCIP_RETCODE SCIPlpiGetBase	(	SCIP_LPI *	lpi,
		int *	cstat,
		int *	rstat
	)

gets current basis status for columns and rows; arrays must be large enough to store the basis status

Parameters

lpi	LP interface structure
cstat	array to store column basis status, or NULL
rstat	array to store row basis status, or NULL

Referenced by lpLexDualSimplex(), SCIPconflictAnalyzeStrongbranch(), SCIPlpGetBase(), and SCIPlpGetSol().

◆ SCIPlpiSetBase()

SCIP_EXPORT SCIP_RETCODE SCIPlpiSetBase	(	SCIP_LPI *	lpi,
		const int *	cstat,
		const int *	rstat
	)

sets current basis status for columns and rows

Parameters

lpi	LP interface structure
cstat	array with column basis status
rstat	array with row basis status

Referenced by SCIPconflictAnalyzeStrongbranch().

◆ SCIPlpiGetBasisInd()

SCIP_EXPORT SCIP_RETCODE SCIPlpiGetBasisInd	(	SCIP_LPI *	lpi,
		int *	bind
	)

returns the indices of the basic columns and rows; basic column n gives value n, basic row m gives value -1-m

Parameters

lpi	LP interface structure
bind	pointer to store basis indices ready to keep number of rows entries

Referenced by SCIPlpGetBasisInd().

◆ SCIPlpiGetBInvRow()

SCIP_EXPORT SCIP_RETCODE SCIPlpiGetBInvRow	(	SCIP_LPI *	lpi,
		int	r,
		SCIP_Real *	coef,
		int *	inds,
		int *	ninds
	)

get row of inverse basis matrix B^-1

Note: The LP interface defines slack variables to have coefficient +1. This means that if, internally, the LP solver uses a -1 coefficient, then rows associated with slacks variables whose coefficient is -1, should be negated; see also the explanation in lpi.h.

Parameters

lpi	LP interface structure
r	row number
coef	pointer to store the coefficients of the row
inds	array to store the non-zero indices, or NULL
ninds	pointer to store the number of non-zero indices, or NULL (-1: if we do not store sparsity information)

Referenced by SCIPlpGetBInvRow().

◆ SCIPlpiGetBInvCol()

SCIP_EXPORT SCIP_RETCODE SCIPlpiGetBInvCol	(	SCIP_LPI *	lpi,
		int	c,
		SCIP_Real *	coef,
		int *	inds,
		int *	ninds
	)

get column of inverse basis matrix B^-1

Note: The LP interface defines slack variables to have coefficient +1. This means that if, internally, the LP solver uses a -1 coefficient, then rows associated with slacks variables whose coefficient is -1, should be negated; see also the explanation in lpi.h.

Parameters

lpi	LP interface structure
c	column number of B^-1; this is NOT the number of the column in the LP; you have to call SCIPlpiGetBasisInd() to get the array which links the B^-1 column numbers to the row and column numbers of the LP! c must be between 0 and nrows-1, since the basis has the size nrows * nrows
coef	pointer to store the coefficients of the column
inds	array to store the non-zero indices, or NULL
ninds	pointer to store the number of non-zero indices, or NULL (-1: if we do not store sparsity information)

Referenced by SCIPlpGetBInvCol().

◆ SCIPlpiGetBInvARow()

SCIP_EXPORT SCIP_RETCODE SCIPlpiGetBInvARow	(	SCIP_LPI *	lpi,
		int	r,
		const SCIP_Real *	binvrow,
		SCIP_Real *	coef,
		int *	inds,
		int *	ninds
	)

get row of inverse basis matrix times constraint matrix B^-1 * A

Note: The LP interface defines slack variables to have coefficient +1. This means that if, internally, the LP solver uses a -1 coefficient, then rows associated with slacks variables whose coefficient is -1, should be negated; see also the explanation in lpi.h.

Parameters

lpi	LP interface structure
r	row number
binvrow	row in (A_B)^-1 from prior call to SCIPlpiGetBInvRow(), or NULL
coef	vector to return coefficients of the row
inds	array to store the non-zero indices, or NULL
ninds	pointer to store the number of non-zero indices, or NULL (-1: if we do not store sparsity information)

Referenced by SCIPlpGetBInvARow().

◆ SCIPlpiGetBInvACol()

SCIP_EXPORT SCIP_RETCODE SCIPlpiGetBInvACol	(	SCIP_LPI *	lpi,
		int	c,
		SCIP_Real *	coef,
		int *	inds,
		int *	ninds
	)

get column of inverse basis matrix times constraint matrix B^-1 * A

Note: The LP interface defines slack variables to have coefficient +1. This means that if, internally, the LP solver uses a -1 coefficient, then rows associated with slacks variables whose coefficient is -1, should be negated; see also the explanation in lpi.h.

Parameters

lpi	LP interface structure
c	column number
coef	vector to return coefficients of the column
inds	array to store the non-zero indices, or NULL
ninds	pointer to store the number of non-zero indices, or NULL (-1: if we do not store sparsity information)

Referenced by SCIPlpGetBInvACol().

◆ SCIPlpiGetState()

SCIP_EXPORT SCIP_RETCODE SCIPlpiGetState	(	SCIP_LPI *	lpi,
		BMS_BLKMEM *	blkmem,
		SCIP_LPISTATE **	lpistate
	)

stores LPi state (like basis information) into lpistate object

Parameters

lpi	LP interface structure
blkmem	block memory
lpistate	pointer to LPi state information (like basis information)

Referenced by SCIPlpGetState(), and SCIPlpStartDive().

◆ SCIPlpiSetState()

SCIP_EXPORT SCIP_RETCODE SCIPlpiSetState	(	SCIP_LPI *	lpi,
		BMS_BLKMEM *	blkmem,
		const SCIP_LPISTATE *	lpistate
	)

loads LPi state (like basis information) into solver; note that the LP might have been extended with additional columns and rows since the state was stored with SCIPlpiGetState()

Parameters

lpi	LP interface structure
blkmem	block memory
lpistate	LPi state information (like basis information), or NULL

Referenced by SCIPlpSetState().

◆ SCIPlpiClearState()

SCIP_EXPORT SCIP_RETCODE SCIPlpiClearState ( SCIP_LPI * lpi )

clears current LPi state (like basis information) of the solver

Parameters

lpi	LP interface structure

Referenced by SCIPtreeEndProbing().

◆ SCIPlpiFreeState()

SCIP_EXPORT SCIP_RETCODE SCIPlpiFreeState	(	SCIP_LPI *	lpi,
		BMS_BLKMEM *	blkmem,
		SCIP_LPISTATE **	lpistate
	)

frees LPi state information

Parameters

lpi	LP interface structure
blkmem	block memory
lpistate	pointer to LPi state information (like basis information)

Referenced by SCIPlpFreeState(), and warmStartInfoFree().

◆ SCIPlpiHasStateBasis()

SCIP_EXPORT SCIP_Bool SCIPlpiHasStateBasis	(	SCIP_LPI *	lpi,
		SCIP_LPISTATE *	lpistate
	)

checks, whether the given LPi state contains simplex basis information

Parameters

lpi	LP interface structure
lpistate	LPi state information (like basis information)

Referenced by SCIPlpSetState().

◆ SCIPlpiReadState()

SCIP_EXPORT SCIP_RETCODE SCIPlpiReadState	(	SCIP_LPI *	lpi,
		const char *	fname
	)

reads LPi state (like basis information from a file

Parameters

lpi	LP interface structure
fname	file name

◆ SCIPlpiWriteState()

SCIP_EXPORT SCIP_RETCODE SCIPlpiWriteState	(	SCIP_LPI *	lpi,
		const char *	fname
	)

writes LPi state (i.e. basis information) to a file

Parameters

lpi	LP interface structure
fname	file name

◆ SCIPlpiGetNorms()

SCIP_RETCODE SCIPlpiGetNorms	(	SCIP_LPI *	lpi,
		BMS_BLKMEM *	blkmem,
		SCIP_LPINORMS **	lpinorms
	)

stores LPi pricing norms into lpinorms object

Parameters

lpi	LP interface structure
blkmem	block memory
lpinorms	pointer to LPi pricing norms information

Referenced by SCIPlpGetNorms().

◆ SCIPlpiSetNorms()

SCIP_RETCODE SCIPlpiSetNorms	(	SCIP_LPI *	lpi,
		BMS_BLKMEM *	blkmem,
		const SCIP_LPINORMS *	lpinorms
	)

loads LPi pricing norms into solver; note that the LP might have been extended with additional columns and rows since the norms were stored with SCIPlpiGetNorms()

Parameters

lpi	LP interface structure
blkmem	block memory
lpinorms	LPi pricing norms information, or NULL

Referenced by SCIPlpSetNorms().

◆ SCIPlpiFreeNorms()

SCIP_RETCODE SCIPlpiFreeNorms	(	SCIP_LPI *	lpi,
		BMS_BLKMEM *	blkmem,
		SCIP_LPINORMS **	lpinorms
	)

frees LPi pricing norms information

Parameters

lpi	LP interface structure
blkmem	block memory
lpinorms	pointer to LPi pricing norms information, or NULL

Referenced by SCIPlpFreeNorms(), and warmStartInfoFree().

◆ SCIPlpiGetIntpar()

SCIP_EXPORT SCIP_RETCODE SCIPlpiGetIntpar	(	SCIP_LPI *	lpi,
		SCIP_LPPARAM	type,
		int *	ival
	)

gets integer parameter of LP

Parameters

lpi	LP interface structure
type	parameter number
ival	buffer to store the parameter value

Referenced by lpCheckIntpar(), and SCIPlpStartDive().

◆ SCIPlpiSetIntpar()

SCIP_EXPORT SCIP_RETCODE SCIPlpiSetIntpar	(	SCIP_LPI *	lpi,
		SCIP_LPPARAM	type,
		int	ival
	)

sets integer parameter of LP

Parameters

lpi	LP interface structure
type	parameter number
ival	parameter value

Referenced by BENDERS_CUTORACLE(), checkAltLPInfeasible(), computeRelIntPoint(), conflictAnalyzeLP(), extendToCover(), initAlternativeLP(), lpSetIntpar(), runBoundHeuristic(), SCIP_DECL_CONSCHECK(), solveClassification(), and solveMinIISC().

◆ SCIPlpiGetRealpar()

SCIP_EXPORT SCIP_RETCODE SCIPlpiGetRealpar	(	SCIP_LPI *	lpi,
		SCIP_LPPARAM	type,
		SCIP_Real *	dval
	)

gets floating point parameter of LP

Parameters

lpi	LP interface structure
type	parameter number
dval	buffer to store the parameter value

Referenced by conflictAnalyzeLP(), and lpCheckRealpar().

◆ SCIPlpiSetRealpar()

SCIP_EXPORT SCIP_RETCODE SCIPlpiSetRealpar	(	SCIP_LPI *	lpi,
		SCIP_LPPARAM	type,
		SCIP_Real	dval
	)

sets floating point parameter of LP

Parameters

lpi	LP interface structure
type	parameter number
dval	parameter value

Referenced by computeRelIntPoint(), conflictAnalyzeLP(), lpSetRealpar(), and runBoundHeuristic().

◆ SCIPlpiInfinity()

SCIP_EXPORT SCIP_Real SCIPlpiInfinity ( SCIP_LPI * lpi )

returns value treated as infinity in the LP solver

Parameters

lpi	LP interface structure

Referenced by addAltLPColumn(), addBdchg(), computeRelIntPoint(), conflictAnalyzeLP(), createAltLPColumn(), lpAlgorithm(), lpFlushAddCols(), lpFlushAddRows(), lpFlushChgCols(), lpFlushChgRows(), lpSetObjlim(), lpSolve(), polyscip::Polyscip::printResults(), runBoundHeuristic(), SCIP_DECL_PARAMCHGD(), SCIPlpCreate(), SCIPlpMarkFlushed(), SCIPlpSolveAndEval(), solveClassification(), solveMinIISC(), solveNodeLP(), unfixAltLPVariable(), unfixAltLPVariables(), and updateLazyBounds().

◆ SCIPlpiIsInfinity()

SCIP_EXPORT SCIP_Bool SCIPlpiIsInfinity	(	SCIP_LPI *	lpi,
		SCIP_Real	val
	)

checks if given value is treated as infinity in the LP solver

Parameters

lpi	LP interface structure
val	value to be checked for infinity

Referenced by addBdchg(), checkLPBoundsClean(), and performStrongbranchWithPropagation().

◆ SCIPlpiReadLP()

SCIP_EXPORT SCIP_RETCODE SCIPlpiReadLP	(	SCIP_LPI *	lpi,
		const char *	fname
	)

reads LP from a file

Parameters

lpi	LP interface structure
fname	file name

◆ SCIPlpiWriteLP()

SCIP_EXPORT SCIP_RETCODE SCIPlpiWriteLP	(	SCIP_LPI *	lpi,
		const char *	fname
	)

writes LP to a file

Parameters

lpi	LP interface structure
fname	file name

Referenced by addAltLPColumn(), computeRelIntPoint(), SCIP_DECL_PARAMCHGD(), SCIPlpWrite(), solveClassification(), solveMinIISC(), and updateObjUpperbound().

SCIP

Detailed Description

Files

Miscellaneous Methods

LPI Creation and Destruction Methods

Modification Methods

Data Accessing Methods

Solving Methods

Solution Information Methods

LP Basis Methods

LPi State Methods

LPi Pricing Norms Methods

Parameter Methods

Numerical Methods

File Interface Methods

Function Documentation

◆ SCIPlpiGetSolverName()

◆ SCIPlpiGetSolverDesc()

◆ SCIPlpiGetSolverPointer()

◆ SCIPlpiSetIntegralityInformation()

◆ SCIPlpiHasPrimalSolve()

◆ SCIPlpiHasDualSolve()

◆ SCIPlpiHasBarrierSolve()

◆ SCIPlpiCreate()

◆ SCIPlpiFree()

◆ SCIPlpiLoadColLP()

◆ SCIPlpiAddCols()

◆ SCIPlpiDelCols()

◆ SCIPlpiDelColset()

◆ SCIPlpiAddRows()

◆ SCIPlpiDelRows()

◆ SCIPlpiDelRowset()

◆ SCIPlpiClear()

◆ SCIPlpiChgBounds()

◆ SCIPlpiChgSides()

◆ SCIPlpiChgCoef()

◆ SCIPlpiChgObjsen()

◆ SCIPlpiChgObj()

◆ SCIPlpiScaleRow()

◆ SCIPlpiScaleCol()

◆ SCIPlpiGetNRows()

◆ SCIPlpiGetNCols()

◆ SCIPlpiGetObjsen()

◆ SCIPlpiGetNNonz()

◆ SCIPlpiGetCols()

◆ SCIPlpiGetRows()

◆ SCIPlpiGetColNames()

◆ SCIPlpiGetRowNames()

◆ SCIPlpiGetObj()

◆ SCIPlpiGetBounds()

◆ SCIPlpiGetSides()

◆ SCIPlpiGetCoef()

◆ SCIPlpiSolvePrimal()

◆ SCIPlpiSolveDual()

◆ SCIPlpiSolveBarrier()

◆ SCIPlpiStartStrongbranch()

◆ SCIPlpiEndStrongbranch()

◆ SCIPlpiStrongbranchFrac()

◆ SCIPlpiStrongbranchesFrac()

◆ SCIPlpiStrongbranchInt()

◆ SCIPlpiStrongbranchesInt()

◆ SCIPlpiWasSolved()

◆ SCIPlpiGetSolFeasibility()

◆ SCIPlpiExistsPrimalRay()

◆ SCIPlpiHasPrimalRay()

◆ SCIPlpiIsPrimalUnbounded()

◆ SCIPlpiIsPrimalInfeasible()

◆ SCIPlpiIsPrimalFeasible()

◆ SCIPlpiExistsDualRay()

◆ SCIPlpiHasDualRay()

◆ SCIPlpiIsDualUnbounded()

◆ SCIPlpiIsDualInfeasible()

◆ SCIPlpiIsDualFeasible()

◆ SCIPlpiIsOptimal()

◆ SCIPlpiIsStable()

◆ SCIPlpiIsObjlimExc()

◆ SCIPlpiIsIterlimExc()

◆ SCIPlpiIsTimelimExc()

◆ SCIPlpiGetInternalStatus()

◆ SCIPlpiIgnoreInstability()