scip_lp.h

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/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
/*                                                                           */
/*                  This file is part of the program and library             */
/*         SCIP --- Solving Constraint Integer Programs                      */
/*                                                                           */
/*    Copyright (C) 2002-2019 Konrad-Zuse-Zentrum                            */
/*                            fuer Informationstechnik Berlin                */
/*                                                                           */
/*  SCIP is distributed under the terms of the ZIB Academic License.         */
/*                                                                           */
/*  You should have received a copy of the ZIB Academic License              */
/*  along with SCIP; see the file COPYING. If not visit scip.zib.de.         */
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/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

/**@file   scip_lp.h
 * @ingroup PUBLICCOREAPI
 * @brief  public methods for the LP relaxation, rows and columns
 * @author Tobias Achterberg
 * @author Timo Berthold
 * @author Thorsten Koch
 * @author Alexander Martin
 * @author Marc Pfetsch
 * @author Kati Wolter
 * @author Gregor Hendel
 * @author Robert Lion Gottwald
 */

/*---+----1----+----2----+----3----+----4----+----5----+----6----+----7----+----8----+----9----+----0----+----1----+----2*/

#ifndef __SCIP_SCIP_LP_H__
#define __SCIP_SCIP_LP_H__


#include "lpi/type_lpi.h"
#include "scip/def.h"
#include "scip/type_cons.h"
#include "scip/type_lp.h"
#include "scip/type_misc.h"
#include "scip/type_retcode.h"
#include "scip/type_scip.h"
#include "scip/type_sepa.h"
#include "scip/type_sol.h"
#include "scip/type_var.h"

/* In debug mode, we include the SCIP's structure in scip.c, such that no one can access
 * this structure except the interface methods in scip.c.
 * In optimized mode, the structure is included in scip.h, because some of the methods
 * are implemented as defines for performance reasons (e.g. the numerical comparisons).
 * Additionally, the internal "set.h" is included, such that the defines in set.h are
 * available in optimized mode.
 */
#ifdef NDEBUG
#include "scip/struct_scip.h"
#include "scip/struct_stat.h"
#include "scip/set.h"
#include "scip/tree.h"
#include "scip/misc.h"
#include "scip/var.h"
#include "scip/cons.h"
#include "scip/solve.h"
#include "scip/debug.h"
#endif

#ifdef __cplusplus
extern "C" {
#endif

/**@addtogroup PublicLPMethods
 *
 * @{
 */

/** returns, whether the LP was or is to be solved in the current node
 *
 *  @return whether the LP was or is to be solved in the current node.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_Bool SCIPhasCurrentNodeLP(
   SCIP*                 scip                /**< SCIP data structure */
   );

/** returns, whether the LP of the current node is already constructed
 *
 *  @return whether the LP of the current node is already constructed.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_Bool SCIPisLPConstructed(
   SCIP*                 scip                /**< SCIP data structure */
   );

/** makes sure that the LP of the current node is loaded and may be accessed through the LP information methods
 *
 *  @warning Contructing the LP might change the amount of variables known in the transformed problem and therefore also
 *           the variables array of SCIP (returned by SCIPgetVars() and SCIPgetVarsData()), so it might be necessary to
 *           call one of the later method after this one
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_RETCODE SCIPconstructLP(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_Bool*            cutoff              /**< pointer to store whether the node can be cut off */
   );

/** makes sure that the LP of the current node is flushed
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_RETCODE SCIPflushLP(
   SCIP*                 scip                /**< SCIP data structure */
   );

/** gets solution status of current LP
 *
 *  @return the solution status of current LP.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_LPSOLSTAT SCIPgetLPSolstat(
   SCIP*                 scip                /**< SCIP data structure */
   );

/** returns whether the current LP solution passed the primal feasibility check
 *
 *  @returns whether the current LP solution passed the primal feasibility check.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_Bool SCIPisLPPrimalReliable(
   SCIP*                 scip                /**< SCIP data structure */
   );

/** returns whether the current LP solution passed the dual feasibility check
 *
 *  @returns whether the current LP solution passed the dual feasibility check.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_Bool SCIPisLPDualReliable(
   SCIP*                 scip                /**< SCIP data structure */
   );

/** returns whether the current lp is a relaxation of the current problem and its optimal objective value is a local lower bound
 *
 *  @return whether the current lp is a relaxation of the current problem and its optimal objective value is a local lower bound.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_Bool SCIPisLPRelax(
   SCIP*                 scip                /**< SCIP data structure */
   );

/** gets objective value of current LP (which is the sum of column and loose objective value)
 *
 *  @return the objective value of current LP (which is the sum of column and loose objective value).
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  @note This method returns the objective value of the current LP solution, which might be primal or dual infeasible
 *        if a limit was hit during solving. It must not be used as a dual bound if the LP solution status returned by
 *        SCIPgetLPSolstat() is SCIP_LPSOLSTAT_ITERLIMIT or SCIP_LPSOLSTAT_TIMELIMIT.
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_Real SCIPgetLPObjval(
   SCIP*                 scip                /**< SCIP data structure */
   );

/** gets part of objective value of current LP that results from COLUMN variables only
 *
 *  @return the part of objective value of current LP that results from COLUMN variables only.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_Real SCIPgetLPColumnObjval(
   SCIP*                 scip                /**< SCIP data structure */
   );

/** gets part of objective value of current LP that results from LOOSE variables only
 *
 *  @return part of objective value of current LP that results from LOOSE variables only.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_Real SCIPgetLPLooseObjval(
   SCIP*                 scip                /**< SCIP data structure */
   );

/** gets the global pseudo objective value; that is all variables set to their best  (w.r.t. the objective
 *  function) global bound
 *
 *  @return the global pseudo objective value; that is all variables set to their best  (w.r.t. the objective
 *  function) global bound.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_INITPRESOLVE
 *       - \ref SCIP_STAGE_PRESOLVING
 *       - \ref SCIP_STAGE_EXITPRESOLVE
 *       - \ref SCIP_STAGE_PRESOLVED
 *       - \ref SCIP_STAGE_INITSOLVE
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_Real SCIPgetGlobalPseudoObjval(
   SCIP*                 scip                /**< SCIP data structure */
   );

/** gets the pseudo objective value for the current search node; that is all variables set to their best (w.r.t. the
 *  objective function) local bound
 *
 *  @return the pseudo objective value for the current search node; that is all variables set to their best (w.r.t. the
 *  objective function) local bound.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_INITPRESOLVE
 *       - \ref SCIP_STAGE_PRESOLVING
 *       - \ref SCIP_STAGE_EXITPRESOLVE
 *       - \ref SCIP_STAGE_PRESOLVED
 *       - \ref SCIP_STAGE_INITSOLVE
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_Real SCIPgetPseudoObjval(
   SCIP*                 scip                /**< SCIP data structure */
   );

/** returns whether the root lp is a relaxation of the problem and its optimal objective value is a global lower bound
 *
 *  @return whether the root lp is a relaxation of the problem and its optimal objective value is a global lower bound.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_Bool SCIPisRootLPRelax(
   SCIP*                 scip                /**< SCIP data structure */
   );

/** gets the objective value of the root node LP or SCIP_INVALID if the root node LP was not (yet) solved
 *
 *  @return the objective value of the root node LP or SCIP_INVALID if the root node LP was not (yet) solved.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_INITPRESOLVE
 *       - \ref SCIP_STAGE_PRESOLVING
 *       - \ref SCIP_STAGE_EXITPRESOLVE
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_Real SCIPgetLPRootObjval(
   SCIP*                 scip                /**< SCIP data structure */
   );

/** gets part of the objective value of the root node LP that results from COLUMN variables only;
 *  returns SCIP_INVALID if the root node LP was not (yet) solved
 *
 *  @return the part of the objective value of the root node LP that results from COLUMN variables only;
 *  or SCIP_INVALID if the root node LP was not (yet) solved.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_INITPRESOLVE
 *       - \ref SCIP_STAGE_PRESOLVING
 *       - \ref SCIP_STAGE_EXITPRESOLVE
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_Real SCIPgetLPRootColumnObjval(
   SCIP*                 scip                /**< SCIP data structure */
   );

/** gets part of the objective value of the root node LP that results from LOOSE variables only;
 *  returns SCIP_INVALID if the root node LP was not (yet) solved
 *
 *  @return the part of the objective value of the root node LP that results from LOOSE variables only;
 *  or SCIP_INVALID if the root node LP was not (yet) solved.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_INITPRESOLVE
 *       - \ref SCIP_STAGE_PRESOLVING
 *       - \ref SCIP_STAGE_EXITPRESOLVE
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_Real SCIPgetLPRootLooseObjval(
   SCIP*                 scip                /**< SCIP data structure */
   );

/** gets current LP columns along with the current number of LP columns
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_RETCODE SCIPgetLPColsData(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_COL***           cols,               /**< pointer to store the array of LP columns, or NULL */
   int*                  ncols               /**< pointer to store the number of LP columns, or NULL */
   );

/** gets current LP columns
 *
 *  @return the current LP columns.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_COL** SCIPgetLPCols(
   SCIP*                 scip                /**< SCIP data structure */
   );

/** gets current number of LP columns
 *
 *  @return the current number of LP columns.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
int SCIPgetNLPCols(
   SCIP*                 scip                /**< SCIP data structure */
   );

/** gets current LP rows along with the current number of LP rows
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_RETCODE SCIPgetLPRowsData(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW***           rows,               /**< pointer to store the array of LP rows, or NULL */
   int*                  nrows               /**< pointer to store the number of LP rows, or NULL */
   );

/** gets current LP rows
 *
 *  @return the current LP rows.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_ROW** SCIPgetLPRows(
   SCIP*                 scip                /**< SCIP data structure */
   );

/** gets current number of LP rows
 *
 *  @return the current number of LP rows.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
int SCIPgetNLPRows(
   SCIP*                 scip                /**< SCIP data structure */
   );

/** returns TRUE iff all columns, i.e. every variable with non-empty column w.r.t. all ever created rows, are present
 *  in the LP, and FALSE, if there are additional already existing columns, that may be added to the LP in pricing
 *
 *  @return TRUE iff all columns, i.e. every variable with non-empty column w.r.t. all ever created rows, are present
 *  in the LP, and FALSE, if there are additional already existing columns, that may be added to the LP in pricing.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_Bool SCIPallColsInLP(
   SCIP*                 scip                /**< SCIP data structure */
   );

/** returns whether the current LP solution is basic, i.e. is defined by a valid simplex basis
 *
 *  @return whether the current LP solution is basic, i.e. is defined by a valid simplex basis.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_Bool SCIPisLPSolBasic(
   SCIP*                 scip                /**< SCIP data structure */
   );

/** gets all indices of basic columns and rows: index i >= 0 corresponds to column i, index i < 0 to row -i-1
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_RETCODE SCIPgetLPBasisInd(
   SCIP*                 scip,               /**< SCIP data structure */
   int*                  basisind            /**< pointer to store basis indices ready to keep number of rows entries */
   );

/** gets a row from the inverse basis matrix B^-1
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_RETCODE SCIPgetLPBInvRow(
   SCIP*                 scip,               /**< SCIP data structure */
   int                   r,                  /**< row number */
   SCIP_Real*            coefs,              /**< array to store the coefficients of the row */
   int*                  inds,               /**< array to store the non-zero indices, or NULL */
   int*                  ninds               /**< pointer to store the number of non-zero indices, or NULL
                                              *  (-1: if we do not store sparsity informations) */
   );

/** gets a column from the inverse basis matrix B^-1
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_RETCODE SCIPgetLPBInvCol(
   SCIP*                 scip,               /**< SCIP data structure */
   int                   c,                  /**< column number of B^-1; this is NOT the number of the column in the LP
                                              *   returned by SCIPcolGetLPPos(); you have to call SCIPgetBasisInd()
                                              *   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 */
   SCIP_Real*            coefs,              /**< array to store the coefficients of the column */
   int*                  inds,               /**< array to store the non-zero indices, or NULL */
   int*                  ninds               /**< pointer to store the number of non-zero indices, or NULL
                                              *  (-1: if we do not store sparsity informations) */
   );

/** gets a row from the product of inverse basis matrix B^-1 and coefficient matrix A (i.e. from B^-1 * A)
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_RETCODE SCIPgetLPBInvARow(
   SCIP*                 scip,               /**< SCIP data structure */
   int                   r,                  /**< row number */
   SCIP_Real*            binvrow,            /**< row in B^-1 from prior call to SCIPgetLPBInvRow(), or NULL */
   SCIP_Real*            coefs,              /**< array to store the coefficients of the row */
   int*                  inds,               /**< array to store the non-zero indices, or NULL */
   int*                  ninds               /**< pointer to store the number of non-zero indices, or NULL
                                              *  (-1: if we do not store sparsity informations) */
   );

/** gets a column from the product of inverse basis matrix B^-1 and coefficient matrix A (i.e. from B^-1 * A),
 *  i.e., it computes B^-1 * A_c with A_c being the c'th column of A
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_RETCODE SCIPgetLPBInvACol(
   SCIP*                 scip,               /**< SCIP data structure */
   int                   c,                  /**< column number which can be accessed by SCIPcolGetLPPos() */
   SCIP_Real*            coefs,              /**< array to store the coefficients of the column */
   int*                  inds,               /**< array to store the non-zero indices, or NULL */
   int*                  ninds               /**< pointer to store the number of non-zero indices, or NULL
                                              *  (-1: if we do not store sparsity informations) */
   );

/** calculates a weighted sum of all LP rows; for negative weights, the left and right hand side of the corresponding
 *  LP row are swapped in the summation
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_RETCODE SCIPsumLPRows(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_Real*            weights,            /**< row weights in row summation */
   SCIP_REALARRAY*       sumcoef,            /**< array to store sum coefficients indexed by variables' probindex */
   SCIP_Real*            sumlhs,             /**< pointer to store the left hand side of the row summation */
   SCIP_Real*            sumrhs              /**< pointer to store the right hand side of the row summation */
   );

/** writes current LP to a file
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_RETCODE SCIPwriteLP(
   SCIP*                 scip,               /**< SCIP data structure */
   const char*           filename            /**< file name */
   );

/** writes MIP relaxation of the current branch-and-bound node to a file
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_RETCODE SCIPwriteMIP(
   SCIP*                 scip,               /**< SCIP data structure */
   const char*           filename,           /**< file name */
   SCIP_Bool             genericnames,       /**< should generic names like x_i and row_j be used in order to avoid
                                              *   troubles with reserved symbols? */
   SCIP_Bool             origobj,            /**< should the original objective function be used? */
   SCIP_Bool             lazyconss           /**< output removable rows as lazy constraints? */
   );

/** gets the LP interface of SCIP;
 *  with the LPI you can use all of the methods defined in lpi/lpi.h;
 *
 *  @warning You have to make sure, that the full internal state of the LPI does not change or is recovered completely
 *           after the end of the method that uses the LPI. In particular, if you manipulate the LP or its solution
 *           (e.g. by calling one of the SCIPlpiAdd...() or one of the SCIPlpiSolve...() methods), you have to check in
 *           advance with SCIPlpiWasSolved() whether the LP is currently solved. If this is the case, you have to make
 *           sure, the internal solution status is recovered completely at the end of your method. This can be achieved
 *           by getting the LPI state before applying any LPI manipulations with SCIPlpiGetState() and restoring it
 *           afterwards with SCIPlpiSetState() and SCIPlpiFreeState(). Additionally you have to resolve the LP with the
 *           appropriate SCIPlpiSolve...() call in order to reinstall the internal solution status.
 *
 *  @warning Make also sure, that all parameter values that you have changed are set back to their original values.
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_TRANSFORMED
 *       - \ref SCIP_STAGE_INITPRESOLVE
 *       - \ref SCIP_STAGE_PRESOLVING
 *       - \ref SCIP_STAGE_EXITPRESOLVE
 *       - \ref SCIP_STAGE_PRESOLVED
 *       - \ref SCIP_STAGE_INITSOLVE
 *       - \ref SCIP_STAGE_SOLVING
 *       - \ref SCIP_STAGE_SOLVED
 *       - \ref SCIP_STAGE_EXITSOLVE
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_RETCODE SCIPgetLPI(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_LPI**            lpi                 /**< pointer to store the LP interface */
   );

/** Displays quality information about the current LP solution. An LP solution need to be available. Information printed
 *  is subject to what the LP solver supports
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_INIT
 *       - \ref SCIP_STAGE_PROBLEM
 *       - \ref SCIP_STAGE_TRANSFORMED
 *       - \ref SCIP_STAGE_INITPRESOLVE
 *       - \ref SCIP_STAGE_PRESOLVING
 *       - \ref SCIP_STAGE_EXITPRESOLVE
 *       - \ref SCIP_STAGE_PRESOLVED
 *       - \ref SCIP_STAGE_SOLVING
 *       - \ref SCIP_STAGE_SOLVED
 *       - \ref SCIP_STAGE_FREE
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 *
 *  @note The printing process is done via the message handler system.
 */
extern
SCIP_RETCODE SCIPprintLPSolutionQuality(
   SCIP*                 scip,               /**< SCIP data structure */
   FILE*                 file                /**< output file (or NULL for standard output) */
   );

/** compute relative interior point to current LP
 *  @see SCIPlpComputeRelIntPoint
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_TRANSFORMED
 *       - \ref SCIP_STAGE_INITPRESOLVE
 *       - \ref SCIP_STAGE_PRESOLVING
 *       - \ref SCIP_STAGE_EXITPRESOLVE
 *       - \ref SCIP_STAGE_PRESOLVED
 *       - \ref SCIP_STAGE_SOLVING
 *       - \ref SCIP_STAGE_SOLVED
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_RETCODE SCIPcomputeLPRelIntPoint(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_Bool             relaxrows,          /**< should the rows be relaxed */
   SCIP_Bool             inclobjcutoff,      /**< should a row for the objective cutoff be included */
   SCIP_Real             timelimit,          /**< time limit for LP solver */
   int                   iterlimit,          /**< iteration limit for LP solver */
   SCIP_SOL**            point               /**< relative interior point on exit */
   );

/**@} */

/**@addtogroup PublicColumnMethods
 *
 * @{
 */

/** returns the reduced costs of a column in the last (feasible) LP
 *
 *  @return the reduced costs of a column in the last (feasible) LP
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_SOLVING
 *       - \ref SCIP_STAGE_SOLVED
 *
 *  @note calling this method in SCIP_STAGE_SOLVED is only recommended to experienced users and should only be called
 *        for pure LP instances (without presolving)
 *
 *  @note The return value of this method should be used carefully if the dual feasibility check was explictely disabled.
 */
extern
SCIP_Real SCIPgetColRedcost(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_COL*             col                 /**< LP column */
   );

/** returns the Farkas coefficient of a column in the last (infeasible) LP
 *
 *  @return the Farkas coefficient of a column in the last (infeasible) LP
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_Real SCIPgetColFarkasCoef(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_COL*             col                 /**< LP column */
   );

/** marks a column to be not removable from the LP in the current node
 *
 *  @pre this method can be called in the following stage of the SCIP solving process:
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
void SCIPmarkColNotRemovableLocal(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_COL*             col                 /**< LP column */
   );

/**@} */

/**@addtogroup PublicRowMethods
 *
 * @{
 */

/** creates and captures an LP row from a constraint handler
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_INITSOLVE
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_RETCODE SCIPcreateRowCons(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW**            row,                /**< pointer to row */
   SCIP_CONSHDLR*        conshdlr,           /**< constraint handler that creates the row */
   const char*           name,               /**< name of row */
   int                   len,                /**< number of nonzeros in the row */
   SCIP_COL**            cols,               /**< array with columns of row entries */
   SCIP_Real*            vals,               /**< array with coefficients of row entries */
   SCIP_Real             lhs,                /**< left hand side of row */
   SCIP_Real             rhs,                /**< right hand side of row */
   SCIP_Bool             local,              /**< is row only valid locally? */
   SCIP_Bool             modifiable,         /**< is row modifiable during node processing (subject to column generation)? */
   SCIP_Bool             removable           /**< should the row be removed from the LP due to aging or cleanup? */
   );

/** creates and captures an LP row from a separator
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_INITSOLVE
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_RETCODE SCIPcreateRowSepa(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW**            row,                /**< pointer to row */
   SCIP_SEPA*            sepa,               /**< separator that creates the row */
   const char*           name,               /**< name of row */
   int                   len,                /**< number of nonzeros in the row */
   SCIP_COL**            cols,               /**< array with columns of row entries */
   SCIP_Real*            vals,               /**< array with coefficients of row entries */
   SCIP_Real             lhs,                /**< left hand side of row */
   SCIP_Real             rhs,                /**< right hand side of row */
   SCIP_Bool             local,              /**< is row only valid locally? */
   SCIP_Bool             modifiable,         /**< is row modifiable during node processing (subject to column generation)? */
   SCIP_Bool             removable           /**< should the row be removed from the LP due to aging or cleanup? */
   );

/** creates and captures an LP row from an unspecified source
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_INITSOLVE
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_RETCODE SCIPcreateRowUnspec(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW**            row,                /**< pointer to row */
   const char*           name,               /**< name of row */
   int                   len,                /**< number of nonzeros in the row */
   SCIP_COL**            cols,               /**< array with columns of row entries */
   SCIP_Real*            vals,               /**< array with coefficients of row entries */
   SCIP_Real             lhs,                /**< left hand side of row */
   SCIP_Real             rhs,                /**< right hand side of row */
   SCIP_Bool             local,              /**< is row only valid locally? */
   SCIP_Bool             modifiable,         /**< is row modifiable during node processing (subject to column generation)? */
   SCIP_Bool             removable           /**< should the row be removed from the LP due to aging or cleanup? */
   );

/** creates and captures an LP row
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_INITSOLVE
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  @deprecated Please use SCIPcreateRowCons() or SCIPcreateRowSepa() when calling from a constraint handler or separator in order
 *              to facilitate correct statistics. If the call is from neither a constraint handler or separator, use SCIPcreateRowUnspec().
 */
extern
SCIP_RETCODE SCIPcreateRow(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW**            row,                /**< pointer to row */
   const char*           name,               /**< name of row */
   int                   len,                /**< number of nonzeros in the row */
   SCIP_COL**            cols,               /**< array with columns of row entries */
   SCIP_Real*            vals,               /**< array with coefficients of row entries */
   SCIP_Real             lhs,                /**< left hand side of row */
   SCIP_Real             rhs,                /**< right hand side of row */
   SCIP_Bool             local,              /**< is row only valid locally? */
   SCIP_Bool             modifiable,         /**< is row modifiable during node processing (subject to column generation)? */
   SCIP_Bool             removable           /**< should the row be removed from the LP due to aging or cleanup? */
   );

/** creates and captures an LP row without any coefficients from a constraint handler
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_INITSOLVE
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_RETCODE SCIPcreateEmptyRowCons(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW**            row,                /**< pointer to row */
   SCIP_CONSHDLR*        conshdlr,           /**< constraint handler that creates the row */
   const char*           name,               /**< name of row */
   SCIP_Real             lhs,                /**< left hand side of row */
   SCIP_Real             rhs,                /**< right hand side of row */
   SCIP_Bool             local,              /**< is row only valid locally? */
   SCIP_Bool             modifiable,         /**< is row modifiable during node processing (subject to column generation)? */
   SCIP_Bool             removable           /**< should the row be removed from the LP due to aging or cleanup? */
   );

/** creates and captures an LP row without any coefficients from a separator
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_INITSOLVE
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_RETCODE SCIPcreateEmptyRowSepa(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW**            row,                /**< pointer to row */
   SCIP_SEPA*            sepa,               /**< separator that creates the row */
   const char*           name,               /**< name of row */
   SCIP_Real             lhs,                /**< left hand side of row */
   SCIP_Real             rhs,                /**< right hand side of row */
   SCIP_Bool             local,              /**< is row only valid locally? */
   SCIP_Bool             modifiable,         /**< is row modifiable during node processing (subject to column generation)? */
   SCIP_Bool             removable           /**< should the row be removed from the LP due to aging or cleanup? */
   );

/** creates and captures an LP row without any coefficients from an unspecified source
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_INITSOLVE
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_RETCODE SCIPcreateEmptyRowUnspec(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW**            row,                /**< pointer to row */
   const char*           name,               /**< name of row */
   SCIP_Real             lhs,                /**< left hand side of row */
   SCIP_Real             rhs,                /**< right hand side of row */
   SCIP_Bool             local,              /**< is row only valid locally? */
   SCIP_Bool             modifiable,         /**< is row modifiable during node processing (subject to column generation)? */
   SCIP_Bool             removable           /**< should the row be removed from the LP due to aging or cleanup? */
   );

/** creates and captures an LP row without any coefficients
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_INITSOLVE
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  @deprecated Please use SCIPcreateEmptyRowCons() or SCIPcreateEmptyRowSepa() when calling from a constraint handler or separator in order
 *              to facilitate correct statistics. If the call is from neither a constraint handler or separator, use SCIPcreateEmptyRowUnspec().
 */
extern
SCIP_RETCODE SCIPcreateEmptyRow(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW**            row,                /**< pointer to row */
   const char*           name,               /**< name of row */
   SCIP_Real             lhs,                /**< left hand side of row */
   SCIP_Real             rhs,                /**< right hand side of row */
   SCIP_Bool             local,              /**< is row only valid locally? */
   SCIP_Bool             modifiable,         /**< is row modifiable during node processing (subject to column generation)? */
   SCIP_Bool             removable           /**< should the row be removed from the LP due to aging or cleanup? */
   );

/** increases usage counter of LP row
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_INITSOLVE
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_RETCODE SCIPcaptureRow(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row                 /**< row to capture */
   );

/** decreases usage counter of LP row, and frees memory if necessary
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_INITSOLVE
 *       - \ref SCIP_STAGE_SOLVING
 *       - \ref SCIP_STAGE_EXITSOLVE
 */
extern
SCIP_RETCODE SCIPreleaseRow(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW**            row                 /**< pointer to LP row */
   );

/** changes left hand side of LP row
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_INITSOLVE
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_RETCODE SCIPchgRowLhs(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row,                /**< LP row */
   SCIP_Real             lhs                 /**< new left hand side */
   );

/** changes right hand side of LP row
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_INITSOLVE
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_RETCODE SCIPchgRowRhs(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row,                /**< LP row */
   SCIP_Real             rhs                 /**< new right hand side */
   );

/** informs row, that all subsequent additions of variables to the row should be cached and not directly applied;
 *  after all additions were applied, SCIPflushRowExtensions() must be called;
 *  while the caching of row extensions is activated, information methods of the row give invalid results;
 *  caching should be used, if a row is build with SCIPaddVarToRow() calls variable by variable to increase
 *  the performance
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_INITSOLVE
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_RETCODE SCIPcacheRowExtensions(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row                 /**< LP row */
   );

/** flushes all cached row extensions after a call of SCIPcacheRowExtensions() and merges coefficients with
 *  equal columns into a single coefficient
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_INITSOLVE
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_RETCODE SCIPflushRowExtensions(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row                 /**< LP row */
   );

/** resolves variable to columns and adds them with the coefficient to the row
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @attention If the absolute value of val is below the SCIP epsilon tolerance, the variable will not added.
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_INITSOLVE
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  @note In case calling this method in the enforcement process of an lp solution, it might be that some variables,
 *        that were not yet in the LP (e.g. dynamic columns) will change their lp solution value returned by SCIP.
 *        For example, a variable, which has a negative objective value, that has no column in the lp yet, is in the lp solution
 *        on its upper bound (variables with status SCIP_VARSTATUS_LOOSE are in an lp solution on it's best bound), but
 *        creating the column, changes the solution value (variable than has status SCIP_VARSTATUS_COLUMN, and the
 *        initialization sets the lp solution value) to 0.0. (This leads to the conclusion that, if a constraint was
 *        violated, the linear relaxation might not be violated anymore.)
 */
extern
SCIP_RETCODE SCIPaddVarToRow(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row,                /**< LP row */
   SCIP_VAR*             var,                /**< problem variable */
   SCIP_Real             val                 /**< value of coefficient */
   );

/** resolves variables to columns and adds them with the coefficients to the row;
 *  this method caches the row extensions and flushes them afterwards to gain better performance
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @attention If a coefficients absolute value is below the SCIP epsilon tolerance, the variable with its value is not added.
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_INITSOLVE
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_RETCODE SCIPaddVarsToRow(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row,                /**< LP row */
   int                   nvars,              /**< number of variables to add to the row */
   SCIP_VAR**            vars,               /**< problem variables to add */
   SCIP_Real*            vals                /**< values of coefficients */
   );

/** resolves variables to columns and adds them with the same single coefficient to the row;
 *  this method caches the row extensions and flushes them afterwards to gain better performance
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @attention If the absolute value of val is below the SCIP epsilon tolerance, the variables will not added.
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_INITSOLVE
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_RETCODE SCIPaddVarsToRowSameCoef(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row,                /**< LP row */
   int                   nvars,              /**< number of variables to add to the row */
   SCIP_VAR**            vars,               /**< problem variables to add */
   SCIP_Real             val                 /**< unique value of all coefficients */
   );

/** tries to find a value, such that all row coefficients, if scaled with this value become integral
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_INITSOLVE
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_RETCODE SCIPcalcRowIntegralScalar(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row,                /**< LP row */
   SCIP_Real             mindelta,           /**< minimal relative allowed difference of scaled coefficient s*c and integral i */
   SCIP_Real             maxdelta,           /**< maximal relative allowed difference of scaled coefficient s*c and integral i */
   SCIP_Longint          maxdnom,            /**< maximal denominator allowed in rational numbers */
   SCIP_Real             maxscale,           /**< maximal allowed scalar */
   SCIP_Bool             usecontvars,        /**< should the coefficients of the continuous variables also be made integral? */
   SCIP_Real*            intscalar,          /**< pointer to store scalar that would make the coefficients integral, or NULL */
   SCIP_Bool*            success             /**< stores whether returned value is valid */
   );

/** tries to scale row, s.t. all coefficients (of integer variables) become integral
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_INITSOLVE
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_RETCODE SCIPmakeRowIntegral(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row,                /**< LP row */
   SCIP_Real             mindelta,           /**< minimal relative allowed difference of scaled coefficient s*c and integral i */
   SCIP_Real             maxdelta,           /**< maximal relative allowed difference of scaled coefficient s*c and integral i */
   SCIP_Longint          maxdnom,            /**< maximal denominator allowed in rational numbers */
   SCIP_Real             maxscale,           /**< maximal value to scale row with */
   SCIP_Bool             usecontvars,        /**< should the coefficients of the continuous variables also be made integral? */
   SCIP_Bool*            success             /**< stores whether row could be made rational */
   );

/** marks a row to be not removable from the LP in the current node
 *
 *  @pre this method can be called in the following stage of the SCIP solving process:
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
void SCIPmarkRowNotRemovableLocal(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row                 /**< LP row */
   );

/** returns number of integral columns in the row
 *
 *  @return number of integral columns in the row
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_INITSOLVE
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
int SCIPgetRowNumIntCols(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row                 /**< LP row */
   );

/** returns minimal absolute value of row vector's non-zero coefficients
 *
 *  @return minimal absolute value of row vector's non-zero coefficients
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_INITSOLVE
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_Real SCIPgetRowMinCoef(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row                 /**< LP row */
   );

/** returns maximal absolute value of row vector's non-zero coefficients
 *
 *  @return maximal absolute value of row vector's non-zero coefficients
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_INITSOLVE
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_Real SCIPgetRowMaxCoef(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row                 /**< LP row */
   );

/** returns the minimal activity of a row w.r.t. the column's bounds
 *
 *  @return the minimal activity of a row w.r.t. the column's bounds
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_Real SCIPgetRowMinActivity(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row                 /**< LP row */
   );

/** returns the maximal activity of a row w.r.t. the column's bounds
 *
 *  @return the maximal activity of a row w.r.t. the column's bounds
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_Real SCIPgetRowMaxActivity(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row                 /**< LP row */
   );

/** recalculates the activity of a row in the last LP solution
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_RETCODE SCIPrecalcRowLPActivity(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row                 /**< LP row */
   );

/** returns the activity of a row in the last LP solution
 *
 *  @return activity of a row in the last LP solution
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_Real SCIPgetRowLPActivity(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row                 /**< LP row */
   );

/** returns the feasibility of a row in the last LP solution
 *
 *  @return the feasibility of a row in the last LP solution: negative value means infeasibility
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_Real SCIPgetRowLPFeasibility(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row                 /**< LP row */
   );

/** recalculates the activity of a row for the current pseudo solution
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_RETCODE SCIPrecalcRowPseudoActivity(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row                 /**< LP row */
   );

/** returns the activity of a row for the current pseudo solution
 *
 *  @return the activity of a row for the current pseudo solution
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_Real SCIPgetRowPseudoActivity(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row                 /**< LP row */
   );

/** returns the feasibility of a row for the current pseudo solution: negative value means infeasibility
 *
 *  @return the feasibility of a row for the current pseudo solution: negative value means infeasibility
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_Real SCIPgetRowPseudoFeasibility(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row                 /**< LP row */
   );

/** recalculates the activity of a row in the last LP or pseudo solution
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_RETCODE SCIPrecalcRowActivity(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row                 /**< LP row */
   );

/** returns the activity of a row in the last LP or pseudo solution
 *
 *  @return the activity of a row in the last LP or pseudo solution
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_Real SCIPgetRowActivity(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row                 /**< LP row */
   );

/** returns the feasibility of a row in the last LP or pseudo solution
 *
 *  @return the feasibility of a row in the last LP or pseudo solution
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_Real SCIPgetRowFeasibility(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row                 /**< LP row */
   );

/** returns the activity of a row for the given primal solution
 *
 *  @return the activitiy of a row for the given primal solution
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_Real SCIPgetRowSolActivity(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row,                /**< LP row */
   SCIP_SOL*             sol                 /**< primal CIP solution */
   );

/** returns the feasibility of a row for the given primal solution
 *
 *  @return the feasibility of a row for the given primal solution
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_SOLVING
 */
extern
SCIP_Real SCIPgetRowSolFeasibility(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row,                /**< LP row */
   SCIP_SOL*             sol                 /**< primal CIP solution */
   );

/** output row to file stream via the message handler system
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre this method can be called in one of the following stages of the SCIP solving process:
 *       - \ref SCIP_STAGE_INITSOLVE
 *       - \ref SCIP_STAGE_SOLVING
 *       - \ref SCIP_STAGE_SOLVED
 *       - \ref SCIP_STAGE_EXITSOLVE
 */
extern
SCIP_RETCODE SCIPprintRow(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row,                /**< LP row */
   FILE*                 file                /**< output file (or NULL for standard output) */
   );

/**@} */

/**@addtogroup PublicLPDivingMethods
 *
 * @{
 */

/** initiates LP diving, making methods SCIPchgVarObjDive(), SCIPchgVarLbDive(), and SCIPchgVarUbDive() available
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 *
 *  @note diving is allowed even if the current LP is not flushed, not solved, or not solved to optimality; be aware
 *  that solving the (first) diving LP may take longer than expect and that the latter two cases could stem from
 *  numerical troubles during the last LP solve; because of this, most users will want to call this method only if
 *  SCIPgetLPSolstat(scip) == SCIP_LPSOLSTAT_OPTIMAL
 */
extern
SCIP_RETCODE SCIPstartDive(
   SCIP*                 scip                /**< SCIP data structure */
   );

/** quits LP diving and resets bounds and objective values of columns to the current node's values
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_RETCODE SCIPendDive(
   SCIP*                 scip                /**< SCIP data structure */
   );

/** changes cutoffbound in current dive
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_RETCODE SCIPchgCutoffboundDive(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_Real             newcutoffbound      /**< new cutoffbound */
   );

/** changes variable's objective value in current dive
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_RETCODE SCIPchgVarObjDive(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_VAR*             var,                /**< variable to change the objective value for */
   SCIP_Real             newobj              /**< new objective value */
   );

/** changes variable's lower bound in current dive
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_RETCODE SCIPchgVarLbDive(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_VAR*             var,                /**< variable to change the bound for */
   SCIP_Real             newbound            /**< new value for bound */
   );

/** changes variable's upper bound in current dive
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_RETCODE SCIPchgVarUbDive(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_VAR*             var,                /**< variable to change the bound for */
   SCIP_Real             newbound            /**< new value for bound */
   );

/** adds a row to the LP in current dive
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_RETCODE SCIPaddRowDive(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row                 /**< row to be added */
   );

/** changes row lhs in current dive, change will be undone after diving ends, for permanent changes use SCIPchgRowLhs()
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_RETCODE SCIPchgRowLhsDive(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row,                /**< row to change the lhs for */
   SCIP_Real             newlhs              /**< new value for lhs */
   );

/** changes row rhs in current dive, change will be undone after diving ends, for permanent changes use SCIPchgRowRhs()
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_RETCODE SCIPchgRowRhsDive(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_ROW*             row,                /**< row to change the lhs for */
   SCIP_Real             newrhs              /**< new value for rhs */
   );

/** gets variable's objective value in current dive
 *
 *  @return the variable's objective value in current dive.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_Real SCIPgetVarObjDive(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_VAR*             var                 /**< variable to get the bound for */
   );

/** gets variable's lower bound in current dive
 *
 *  @return the variable's lower bound in current dive.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_Real SCIPgetVarLbDive(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_VAR*             var                 /**< variable to get the bound for */
   );

/** gets variable's upper bound in current dive
 *
 *  @return the variable's upper bound in current dive.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_Real SCIPgetVarUbDive(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_VAR*             var                 /**< variable to get the bound for */
   );
/** solves the LP of the current dive; no separation or pricing is applied
 *
 *  @return \ref SCIP_OKAY is returned if everything worked. Otherwise a suitable error code is passed. See \ref
 *          SCIP_Retcode "SCIP_RETCODE" for a complete list of error codes.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_SOLVING
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 *
 *  @note be aware that the LP solve may take longer than expected if SCIPgetLPSolstat(scip) != SCIP_LPSOLSTAT_OPTIMAL,
 *  compare the explanation of SCIPstartDive()
 */
extern
SCIP_RETCODE SCIPsolveDiveLP(
   SCIP*                 scip,               /**< SCIP data structure */
   int                   itlim,              /**< maximal number of LP iterations to perform, or -1 for no limit */
   SCIP_Bool*            lperror,            /**< pointer to store whether an unresolved LP error occurred */
   SCIP_Bool*            cutoff              /**< pointer to store whether the diving LP was infeasible or the objective
                                              *   limit was reached (or NULL, if not needed) */
   );

/** returns the number of the node in the current branch and bound run, where the last LP was solved in diving
 *  or probing mode
 *
 *  @return the number of the node in the current branch and bound run, where the last LP was solved in diving
 *  or probing mode.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_TRANSFORMING
 *       - \ref SCIP_STAGE_TRANSFORMED
 *       - \ref SCIP_STAGE_INITPRESOLVE
 *       - \ref SCIP_STAGE_PRESOLVING
 *       - \ref SCIP_STAGE_EXITPRESOLVE
 *       - \ref SCIP_STAGE_PRESOLVED
 *       - \ref SCIP_STAGE_INITSOLVE
 *       - \ref SCIP_STAGE_SOLVING
 *       - \ref SCIP_STAGE_SOLVED
 *       - \ref SCIP_STAGE_EXITSOLVE
 *       - \ref SCIP_STAGE_FREETRANS
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_Longint SCIPgetLastDivenode(
   SCIP*                 scip                /**< SCIP data structure */
   );

/** returns whether we are in diving mode
 *
 *  @return whether we are in diving mode.
 *
 *  @pre This method can be called if @p scip is in one of the following stages:
 *       - \ref SCIP_STAGE_TRANSFORMING
 *       - \ref SCIP_STAGE_TRANSFORMED
 *       - \ref SCIP_STAGE_INITPRESOLVE
 *       - \ref SCIP_STAGE_PRESOLVING
 *       - \ref SCIP_STAGE_EXITPRESOLVE
 *       - \ref SCIP_STAGE_PRESOLVED
 *       - \ref SCIP_STAGE_INITSOLVE
 *       - \ref SCIP_STAGE_SOLVING
 *       - \ref SCIP_STAGE_SOLVED
 *       - \ref SCIP_STAGE_EXITSOLVE
 *       - \ref SCIP_STAGE_FREETRANS
 *
 *  See \ref SCIP_Stage "SCIP_STAGE" for a complete list of all possible solving stages.
 */
extern
SCIP_Bool SCIPinDive(
   SCIP*                 scip                /**< SCIP data structure */
   );

/**@} */

#ifdef __cplusplus
}
#endif

#endif