/*! \legal
Copyright (C) 2000 -- 2003, International Business Machines Corporation
and others. All Rights Reserved.
*/
/*! \file CoinWarmStart.hpp
\brief Declaration of the generic simplex (basis-oriented) warm start
class. Also contains a basis diff class.
*/
#ifndef CoinWarmStartBasis_H
#define CoinWarmStartBasis_H
#include <vector>
#include "CoinSort.hpp"
#include "CoinHelperFunctions.hpp"
#include "CoinWarmStart.hpp"
//#############################################################################
/*! \class CoinWarmStartBasis
\brief The default COIN simplex (basis-oriented) warm start class
CoinWarmStartBasis provides for a warm start object which contains the
status of each variable (structural and artificial).
\todo Modify this class so that the number of status entries per byte
and bytes per status vector allocation unit are not hardcoded.
At the least, collect this into a couple of macros.
\todo Consider separate fields for allocated capacity and actual basis
size. We could avoid some reallocation, at the price of retaining
more space than we need. Perhaps more important, we could do much
better sanity checks.
*/
class CoinWarmStartBasis : public CoinWarmStart {
public:
/*! \brief Enum for status of variables
Matches CoinPrePostsolveMatrix::Status, without superBasic. Most code that
converts between CoinPrePostsolveMatrix::Status and
CoinWarmStartBasis::Status will break if this correspondence is broken.
The status vectors are currently packed using two bits per status code,
four codes per byte. The location of the status information for
variable \c i is in byte <code>i>>2</code> and occupies bits 0:1
if <code>i\%4 == 0</code>, bits 2:3 if <code>i\%4 == 1</code>, etc.
The non-member functions getStatus(const char*,int) and
setStatus(char*,int,CoinWarmStartBasis::Status) are provided to hide
details of the packing.
*/
enum Status {
isFree = 0x00, ///< Nonbasic free variable
basic = 0x01, ///< Basic variable
atUpperBound = 0x02, ///< Nonbasic at upper bound
atLowerBound = 0x03 ///< Nonbasic at lower bound
};
/** \brief Transfer vector entry for
mergeBasis(const CoinWarmStartBasis*,const XferVec*,const XferVec*)
*/
typedef CoinTriple<int,int,int> XferEntry ;
/** \brief Transfer vector for
mergeBasis(const CoinWarmStartBasis*,const XferVec*,const XferVec*)
*/
typedef std::vector<XferEntry> XferVec ;
public:
/*! \name Methods to get and set basis information.
The status of variables is kept in a pair of arrays, one for structural
variables, and one for artificials (aka logicals and slacks). The status
is coded using the values of the Status enum.
\sa CoinWarmStartBasis::Status for a description of the packing used in
the status arrays.
*/
//@{
/// Return the number of structural variables
inline int getNumStructural() const { return numStructural_; }
/// Return the number of artificial variables
inline int getNumArtificial() const { return numArtificial_; }
/** Return the number of basic structurals
A fast test for an all-slack basis.
*/
int numberBasicStructurals() const ;
/// Return the status of the specified structural variable.
inline Status getStructStatus(int i) const {
const int st = (structuralStatus_[i>>2] >> ((i&3)<<1)) & 3;
return static_cast<CoinWarmStartBasis::Status>(st);
}
/// Set the status of the specified structural variable.
inline void setStructStatus(int i, Status st) {
char& st_byte = structuralStatus_[i>>2];
st_byte &= ~(3 << ((i&3)<<1));
st_byte |= (st << ((i&3)<<1));
}
/** Return the status array for the structural variables
The status information is stored using the codes defined in the
Status enum, 2 bits per variable, packed 4 variables per byte.
*/
inline char * getStructuralStatus() { return structuralStatus_; }
/** \c const overload for
\link CoinWarmStartBasis::getStructuralStatus()
getStructuralStatus()
\endlink
*/
inline const char * getStructuralStatus() const { return structuralStatus_; }
/** As for \link getStructuralStatus() getStructuralStatus \endlink,
but returns the status array for the artificial variables.
*/
inline char * getArtificialStatus() { return artificialStatus_; }
/// Return the status of the specified artificial variable.
inline Status getArtifStatus(int i) const {
const int st = (artificialStatus_[i>>2] >> ((i&3)<<1)) & 3;
return static_cast<CoinWarmStartBasis::Status>(st);
}
/// Set the status of the specified artificial variable.
inline void setArtifStatus(int i, Status st) {
char& st_byte = artificialStatus_[i>>2];
st_byte &= ~(3 << ((i&3)<<1));
st_byte |= (st << ((i&3)<<1));
}
/** \c const overload for
\link CoinWarmStartBasis::getArtificialStatus()
getArtificialStatus()
\endlink
*/
inline const char * getArtificialStatus() const { return artificialStatus_; }
//@}
/*! \name Basis `diff' methods */
//@{
/*! \brief Generate a `diff' that can convert the warm start basis passed as
a parameter to the warm start basis specified by \c this.
The capabilities are limited: the basis passed as a parameter can be no
larger than the basis pointed to by \c this.
*/
virtual CoinWarmStartDiff*
generateDiff (const CoinWarmStart *const oldCWS) const ;
/*! \brief Apply \p diff to this basis
Update this basis by applying \p diff. It's assumed that the allocated
capacity of the basis is sufficiently large.
*/
virtual void
applyDiff (const CoinWarmStartDiff *const cwsdDiff) ;
//@}
/*! \name Methods to modify the warm start object */
//@{
/*! \brief Set basis capacity; existing basis is discarded.
After execution of this routine, the warm start object does not describe
a valid basis: all structural and artificial variables have status isFree.
*/
virtual void setSize(int ns, int na) ;
/*! \brief Set basis capacity; existing basis is maintained.
After execution of this routine, the warm start object describes a valid
basis: the status of new structural variables (added columns) is set to
nonbasic at lower bound, and the status of new artificial variables
(added rows) is set to basic. (The basis can be invalid if new structural
variables do not have a finite lower bound.)
*/
virtual void resize (int newNumberRows, int newNumberColumns);
/** \brief Delete a set of rows from the basis
\warning
This routine assumes that the set of indices to be deleted is sorted in
ascending order and contains no duplicates. Use deleteRows() if this is
not the case.
\warning
The resulting basis is guaranteed valid only if all deleted
constraints are slack (hence the associated logicals are basic).
Removal of a tight constraint with a nonbasic logical implies that
some basic variable must be made nonbasic. This correction is left to
the client.
*/
virtual void compressRows (int tgtCnt, const int *tgts) ;
/** \brief Delete a set of rows from the basis
\warning
The resulting basis is guaranteed valid only if all deleted
constraints are slack (hence the associated logicals are basic).
Removal of a tight constraint with a nonbasic logical implies that
some basic variable must be made nonbasic. This correction is left to
the client.
*/
virtual void deleteRows(int rawTgtCnt, const int *rawTgts) ;
/** \brief Delete a set of columns from the basis
\warning
The resulting basis is guaranteed valid only if all deleted variables
are nonbasic.
Removal of a basic variable implies that some nonbasic variable must be
made basic. This correction is left to the client.
*/
virtual void deleteColumns(int number, const int * which);
/** \brief Merge entries from a source basis into this basis.
\warning
It's the client's responsibility to ensure validity of the merged basis,
if that's important to the application.
The vector xferCols (xferRows) specifies runs of entries to be taken from
the source basis and placed in this basis. Each entry is a CoinTriple,
with first specifying the starting source index of a run, second
specifying the starting destination index, and third specifying the run
length.
*/
virtual void mergeBasis(const CoinWarmStartBasis *src,
const XferVec *xferRows,
const XferVec *xferCols) ;
//@}
/*! \name Constructors, destructors, and related functions */
//@{
/** Default constructor
Creates a warm start object representing an empty basis
(0 rows, 0 columns).
*/
CoinWarmStartBasis();
/** Constructs a warm start object with the specified status vectors.
The parameters are copied.
Consider assignBasisStatus(int,int,char*&,char*&) if the object should
assume ownership.
\sa CoinWarmStartBasis::Status for a description of the packing used in
the status arrays.
*/
CoinWarmStartBasis(int ns, int na, const char* sStat, const char* aStat) ;
/** Copy constructor */
CoinWarmStartBasis(const CoinWarmStartBasis& ws) ;
/** `Virtual constructor' */
virtual CoinWarmStart *clone() const
{
return new CoinWarmStartBasis(*this);
}
/** Destructor */
virtual ~CoinWarmStartBasis();
/** Assignment */
virtual CoinWarmStartBasis& operator=(const CoinWarmStartBasis& rhs) ;
/** Assign the status vectors to be the warm start information.
In this method the CoinWarmStartBasis object assumes ownership of the
pointers and upon return the argument pointers will be NULL.
If copying is desirable, use the
\link CoinWarmStartBasis(int,int,const char*,const char*)
array constructor \endlink
or the
\link operator=(const CoinWarmStartBasis&)
assignment operator \endlink.
\note
The pointers passed to this method will be
freed using delete[], so they must be created using new[].
*/
virtual void assignBasisStatus(int ns, int na, char*& sStat, char*& aStat) ;
//@}
/*! \name Miscellaneous methods */
//@{
/// Prints in readable format (for debug)
virtual void print() const;
//@}
protected:
/** \name Protected data members
\sa CoinWarmStartBasis::Status for a description of the packing used in
the status arrays.
*/
//@{
/// The number of structural variables
int numStructural_;
/// The number of artificial variables
int numArtificial_;
/** The status of the structural variables. */
char * structuralStatus_;
/** The status of the artificial variables. */
char * artificialStatus_;
//@}
};
/*! \relates CoinWarmStartBasis
\brief Get the status of the specified variable in the given status array.
*/
inline CoinWarmStartBasis::Status getStatus(const char *array, int i) {
const int st = (array[i>>2] >> ((i&3)<<1)) & 3;
return static_cast<CoinWarmStartBasis::Status>(st);
}
/*! \relates CoinWarmStartBasis
\brief Set the status of the specified variable in the given status array.
*/
inline void setStatus(char * array, int i, CoinWarmStartBasis::Status st) {
char& st_byte = array[i>>2];
st_byte &= ~(3 << ((i&3)<<1));
st_byte |= (st << ((i&3)<<1));
}
/*! \class CoinWarmStartBasisDiff
\brief A `diff' between two CoinWarmStartBasis objects
This class exists in order to hide from the world the details of
calculating and representing a `diff' between two CoinWarmStartBasis
objects. For convenience, assignment, cloning, and deletion are visible to
the world, and default and copy constructors are made available to derived
classes. Knowledge of the rest of this structure, and of generating and
applying diffs, is restricted to the friend functions
CoinWarmStartBasis::generateDiff() and CoinWarmStartBasis::applyDiff().
The actual data structure is a pair of unsigned int vectors, #diffNdxs_ and
#diffVals_.
\todo This is a pretty generic structure, and vector diff is a pretty generic
activity. We should be able to convert this to a template.
\todo Using unsigned int as the data type for the diff vectors might help
to contain the damage when this code is inevitably compiled for 64 bit
architectures. But the notion of int as 4 bytes is hardwired into
CoinWarmStartBasis, so changes are definitely required.
*/
class CoinWarmStartBasisDiff : public CoinWarmStartDiff
{ public:
/*! \brief `Virtual constructor' */
virtual CoinWarmStartDiff *clone() const
{ CoinWarmStartBasisDiff *cwsbd = new CoinWarmStartBasisDiff(*this) ;
return (dynamic_cast<CoinWarmStartDiff *>(cwsbd)) ; }
/*! \brief Assignment */
virtual
CoinWarmStartBasisDiff &operator= (const CoinWarmStartBasisDiff &rhs) ;
/*! \brief Destructor */
virtual ~CoinWarmStartBasisDiff()
{ delete[] diffNdxs_ ;
delete[] diffVals_ ; }
protected:
/*! \brief Default constructor
This is protected (rather than private) so that derived classes can
see it when they make <i>their</i> default constructor protected or
private.
*/
CoinWarmStartBasisDiff () : sze_(0), diffNdxs_(0), diffVals_(0) { }
/*! \brief Copy constructor
For convenience when copying objects containing CoinWarmStartBasisDiff
objects. But consider whether you should be using #clone() to retain
polymorphism.
This is protected (rather than private) so that derived classes can
see it when they make <i>their</i> copy constructor protected or
private.
*/
CoinWarmStartBasisDiff (const CoinWarmStartBasisDiff &cwsbd) ;
/*! \brief Standard constructor */
CoinWarmStartBasisDiff (int sze, const unsigned int *const diffNdxs,
const unsigned int *const diffVals) ;
private:
friend CoinWarmStartDiff*
CoinWarmStartBasis::generateDiff(const CoinWarmStart *const oldCWS) const ;
friend void
CoinWarmStartBasis::applyDiff(const CoinWarmStartDiff *const diff) ;
/*! \brief Number of entries (and allocated capacity), in units of \c int. */
int sze_ ;
/*! \brief Array of diff indices */
unsigned int *diffNdxs_ ;
/*! \brief Array of diff values */
unsigned int *diffVals_ ;
} ;
#endif
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