# SCIP

Solving Constraint Integer Programs

LP Solver Interface

## 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/".

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

const char * SCIPlpiGetSolverName (void)

const char * SCIPlpiGetSolverDesc (void)

void * SCIPlpiGetSolverPointer (SCIP_LPI *lpi)

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

SCIP_Bool SCIPlpiHasPrimalSolve (void)

SCIP_Bool SCIPlpiHasDualSolve (void)

SCIP_Bool SCIPlpiHasBarrierSolve (void)

## LPI Creation and Destruction Methods

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

SCIP_RETCODE SCIPlpiFree (SCIP_LPI **lpi)

## Modification Methods

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_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_RETCODE SCIPlpiDelCols (SCIP_LPI *lpi, int firstcol, int lastcol)

SCIP_RETCODE SCIPlpiDelColset (SCIP_LPI *lpi, int *dstat)

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_RETCODE SCIPlpiDelRows (SCIP_LPI *lpi, int firstrow, int lastrow)

SCIP_RETCODE SCIPlpiDelRowset (SCIP_LPI *lpi, int *dstat)

SCIP_RETCODE SCIPlpiClear (SCIP_LPI *lpi)

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

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

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

SCIP_RETCODE SCIPlpiChgObjsen (SCIP_LPI *lpi, SCIP_OBJSEN objsen)

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

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

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

## Data Accessing Methods

SCIP_RETCODE SCIPlpiGetNRows (SCIP_LPI *lpi, int *nrows)

SCIP_RETCODE SCIPlpiGetNCols (SCIP_LPI *lpi, int *ncols)

SCIP_RETCODE SCIPlpiGetObjsen (SCIP_LPI *lpi, SCIP_OBJSEN *objsen)

SCIP_RETCODE SCIPlpiGetNNonz (SCIP_LPI *lpi, int *nnonz)

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_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_RETCODE SCIPlpiGetColNames (SCIP_LPI *lpi, int firstcol, int lastcol, char **colnames, char *namestorage, int namestoragesize, int *storageleft)

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

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

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

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

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

## Solving Methods

SCIP_RETCODE SCIPlpiSolvePrimal (SCIP_LPI *lpi)

SCIP_RETCODE SCIPlpiSolveDual (SCIP_LPI *lpi)

SCIP_RETCODE SCIPlpiSolveBarrier (SCIP_LPI *lpi, SCIP_Bool crossover)

SCIP_RETCODE SCIPlpiStartStrongbranch (SCIP_LPI *lpi)

SCIP_RETCODE SCIPlpiEndStrongbranch (SCIP_LPI *lpi)

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_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_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_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_Bool SCIPlpiWasSolved (SCIP_LPI *lpi)

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

SCIP_Bool SCIPlpiExistsPrimalRay (SCIP_LPI *lpi)

SCIP_Bool SCIPlpiHasPrimalRay (SCIP_LPI *lpi)

SCIP_Bool SCIPlpiIsPrimalUnbounded (SCIP_LPI *lpi)

SCIP_Bool SCIPlpiIsPrimalInfeasible (SCIP_LPI *lpi)

SCIP_Bool SCIPlpiIsPrimalFeasible (SCIP_LPI *lpi)

SCIP_Bool SCIPlpiExistsDualRay (SCIP_LPI *lpi)

SCIP_Bool SCIPlpiHasDualRay (SCIP_LPI *lpi)

SCIP_Bool SCIPlpiIsDualUnbounded (SCIP_LPI *lpi)

SCIP_Bool SCIPlpiIsDualInfeasible (SCIP_LPI *lpi)

SCIP_Bool SCIPlpiIsDualFeasible (SCIP_LPI *lpi)

SCIP_Bool SCIPlpiIsOptimal (SCIP_LPI *lpi)

SCIP_Bool SCIPlpiIsStable (SCIP_LPI *lpi)

SCIP_Bool SCIPlpiIsObjlimExc (SCIP_LPI *lpi)

SCIP_Bool SCIPlpiIsIterlimExc (SCIP_LPI *lpi)

SCIP_Bool SCIPlpiIsTimelimExc (SCIP_LPI *lpi)

int SCIPlpiGetInternalStatus (SCIP_LPI *lpi)

SCIP_RETCODE SCIPlpiIgnoreInstability (SCIP_LPI *lpi, SCIP_Bool *success)

SCIP_RETCODE SCIPlpiGetObjval (SCIP_LPI *lpi, SCIP_Real *objval)

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

SCIP_RETCODE SCIPlpiGetPrimalRay (SCIP_LPI *lpi, SCIP_Real *ray)

SCIP_RETCODE SCIPlpiGetDualfarkas (SCIP_LPI *lpi, SCIP_Real *dualfarkas)

SCIP_RETCODE SCIPlpiGetIterations (SCIP_LPI *lpi, int *iterations)

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

## LP Basis Methods

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

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

SCIP_RETCODE SCIPlpiGetBasisInd (SCIP_LPI *lpi, int *bind)

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

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

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

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

## LPi State Methods

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

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

SCIP_RETCODE SCIPlpiClearState (SCIP_LPI *lpi)

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

SCIP_Bool SCIPlpiHasStateBasis (SCIP_LPI *lpi, SCIP_LPISTATE *lpistate)

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

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_RETCODE SCIPlpiGetIntpar (SCIP_LPI *lpi, SCIP_LPPARAM type, int *ival)

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

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

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

## Numerical Methods

SCIP_Real SCIPlpiInfinity (SCIP_LPI *lpi)

SCIP_Bool SCIPlpiIsInfinity (SCIP_LPI *lpi, SCIP_Real val)

## File Interface Methods

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

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

## ◆ SCIPlpiGetSolverName()

 const char* SCIPlpiGetSolverName ( void )

gets name and version of LP solver

## ◆ SCIPlpiGetSolverDesc()

 const char* SCIPlpiGetSolverDesc ( void )

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

Referenced by doScipCreate().

## ◆ SCIPlpiGetSolverPointer()

 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_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_Bool SCIPlpiHasPrimalSolve ( void )

informs about availability of a primal simplex solving method

## ◆ SCIPlpiHasDualSolve()

 SCIP_Bool SCIPlpiHasDualSolve ( void )

informs about availability of a dual simplex solving method

## ◆ SCIPlpiHasBarrierSolve()

 SCIP_Bool SCIPlpiHasBarrierSolve ( void )

informs about availability of a barrier solving method

## ◆ SCIPlpiCreate()

 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

## ◆ SCIPlpiFree()

 SCIP_RETCODE SCIPlpiFree ( SCIP_LPI ** lpi )

deletes an LP problem object

Parameters
 lpi pointer to an LP interface structure

 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().

 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 )

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

## ◆ SCIPlpiDelCols()

 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_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().

 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 )

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

## ◆ SCIPlpiDelRows()

 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_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_RETCODE SCIPlpiClear ( SCIP_LPI * lpi )

clears the whole LP

Parameters
 lpi LP interface structure

## ◆ SCIPlpiChgBounds()

 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

## ◆ SCIPlpiChgSides()

 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

## ◆ SCIPlpiChgCoef()

 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_RETCODE SCIPlpiChgObjsen ( SCIP_LPI * lpi, SCIP_OBJSEN objsen )

changes the objective sense

Parameters
 lpi LP interface structure objsen new objective sense

## ◆ SCIPlpiChgObj()

 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

## ◆ SCIPlpiScaleRow()

 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_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_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

## ◆ SCIPlpiGetNCols()

 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

## ◆ SCIPlpiGetObjsen()

 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_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_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_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_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_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_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_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_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_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_RETCODE SCIPlpiSolvePrimal ( SCIP_LPI * lpi )

calls primal simplex to solve the LP

Parameters
 lpi LP interface structure

## ◆ SCIPlpiSolveDual()

 SCIP_RETCODE SCIPlpiSolveDual ( SCIP_LPI * lpi )

calls dual simplex to solve the LP

Parameters
 lpi LP interface structure

## ◆ SCIPlpiSolveBarrier()

 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_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_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_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_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_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_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_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_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_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_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_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_Bool SCIPlpiIsPrimalInfeasible ( SCIP_LPI * lpi )

returns TRUE iff LP is proven to be primal infeasible

Parameters
 lpi LP interface structure

## ◆ SCIPlpiIsPrimalFeasible()

 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_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_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_Bool SCIPlpiIsDualUnbounded ( SCIP_LPI * lpi )

returns TRUE iff LP is proven to be dual unbounded

Parameters
 lpi LP interface structure

## ◆ SCIPlpiIsDualInfeasible()

 SCIP_Bool SCIPlpiIsDualInfeasible ( SCIP_LPI * lpi )

returns TRUE iff LP is proven to be dual infeasible

Parameters
 lpi LP interface structure

## ◆ SCIPlpiIsDualFeasible()

 SCIP_Bool SCIPlpiIsDualFeasible ( SCIP_LPI * lpi )

returns TRUE iff LP is proven to be dual feasible

Parameters
 lpi LP interface structure

## ◆ SCIPlpiIsOptimal()

 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_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_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_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_Bool SCIPlpiIsTimelimExc ( SCIP_LPI * lpi )

returns TRUE iff the time limit was reached

Parameters
 lpi LP interface structure

Referenced by computeRelIntPoint(), and lpSolve().

## ◆ SCIPlpiGetInternalStatus()

 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_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 lpSolveStable().

## ◆ SCIPlpiGetObjval()

 SCIP_RETCODE SCIPlpiGetObjval ( SCIP_LPI * lpi, SCIP_Real * objval )

gets objective value of solution

Parameters
 lpi LP interface structure objval stores the objective value

## ◆ SCIPlpiGetSol()

 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

## ◆ SCIPlpiGetPrimalRay()

 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_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_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

## ◆ SCIPlpiGetRealSolQuality()

 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_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_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_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_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_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_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 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_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 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_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_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_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_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_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().

 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_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_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_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

## ◆ SCIPlpiGetRealpar()

 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_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_Real SCIPlpiInfinity ( SCIP_LPI * lpi )

returns value treated as infinity in the LP solver

Parameters
 lpi LP interface structure

## ◆ SCIPlpiIsInfinity()

 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().

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