mt_SL.h

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/* MTgomory "multi tableau gomory cut" provides an implementation for gomory
 * cuts derived from multiple tableau rows in the spirit of the work of
 * Andersen et al (IPCO 2007), Cornuejols (es presented in George Nemhauser
 * Birthday Conference in Atlanta 2007) and Gomory (presented in the same
 * conference).
 *
 * Copyright (C) 2007 Daniel Espinoza.
 * 
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by the
 * Free Software Foundation; either version 2.1 of the License, or (at your
 * option) any later version.
 *
 * This library is distributed in the hope that it will be useful, but 
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public 
 * License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA 
 * */
/* ========================================================================= */
#ifndef __MT_SL_H__
#define __MT_SL_H__
#include "EGlib.h"
#include "mt_gomory.h"
#include "mt_cplex_cbk.h"
#include "mt_cutpool.h"
#include "mt_tableau.h"
/** @file 
 * @ingroup MTgomory */
/** @addtogroup MTgomory */
/** @{ */
/* ========================================================================= */
/** @brief The idea of these cuts is to use some ideas from the paper ``On the
 * relative strengt of split, triangle and cuadrilateral cuts'' from Cornuejols
 * et. al. The main point is that splits are bad (compared against triangles or
 * quadrilaterals) whenever we have (an almost) integer part in \f$f_i\f$ for
 * some coordiante \f$i\f$, and a wide base, this can be seen on the following
 * figure:
 * \f$
 * \hspace*{\textwidth}
 * \vspace*{2in}
 * x_1 = 1
   \psset{arrows=->,fillstyle=solid,fillcolor=black,linecolor=black}
   \begin{pspicture}(0,0)(5,3)
   \multido{\i=0+1}{6}{{ \pscircle(\i,0){1mm} }}
   \multido{\i=0+1}{6}{{ \pscircle(\i,1){1mm} }}
   \multido{\i=0+1}{6}{{ \pscircle(\i,2){1mm} }}
   \multido{\i=0+1}{6}{{ \pscircle(\i,3){1mm} }}
   \rput(2.5,2){$f$}
   \psline(2.5,2)(0,.5)\nbput{$r_1$}
   \psline(2.5,2)(4,1)\nbput{$r_2$}
   \psline[arrows=|-|](1,1)(4,1)\nbput{M}
   \end{pspicture} 
   \f$
 * @param data calback data, we assume that the solution and lp has already
 * been loaded into the structure.
 * @param env CPLEX environment
 * @param lp CPLEX lp pointer to the current LP
 * @return zero on success, non-zero otherwise.
 * */
int MTslCut(
    MTgomory_ccbk_t*const data,
    CPXCENVptr env,
    CPXLPptr lp);
/* ========================================================================= */
/** @brief Interface for the CPLEX-callback for the #MTt1Cut function.
 * @param env as returned by CPXopenCPLEX function.
 * @param cbdata A pointer passed from the optimization routine to the
 * user-written callback that identifies the problem being optimized. The only 
 * purpose of this pointer is to pass it to the callback information routines.
 * @param wherefrom An integer value indicating where in the optimization this
 * function was called. It has the value CPX_CALLBACK_MIP_CUT.
 * @param cbhandle A pointer to user private data.
 * @param useraction_p A pointer to an integer indicating the action for ILOG
 * CPLEX to take at the completion
 * of the user callback. The table summarizes possible actions.
 * - 0 CPX_CALLBACK_DEFAULT Use cuts as added
 * - 1 CPX_CALLBACK_FAIL Exit optimization
 * - 2 CPX_CALLBACK_SET Use cuts as added
 * */
int MTsl_ccbk(CPXCENVptr env,
              void*cbdata,
              int wherefrom,
              void*cbhandle,
              int*useraction_p);
/** @} */
/* end of mt_SL.h */
/* ========================================================================= */
#endif

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