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#include "cvc4_private.h"
#ifndef __CVC4__THEORY__ARITH__ROW_VECTOR_H
#define __CVC4__THEORY__ARITH__ROW_VECTOR_H
#include "theory/arith/arith_utilities.h"
#include "theory/arith/arithvar_set.h"
#include "util/rational.h"
#include <vector>
namespace CVC4 {
namespace theory {
namespace arith {
class VarCoeffPair {
private:
ArithVar d_variable;
Rational d_coeff;
public:
VarCoeffPair(ArithVar v, const Rational& q): d_variable(v), d_coeff(q) {}
ArithVar getArithVar() const { return d_variable; }
Rational& getCoefficient() { return d_coeff; }
const Rational& getCoefficient() const { return d_coeff; }
bool operator<(const VarCoeffPair& other) const{
return getArithVar() < other.getArithVar();
}
static bool variableLess(const VarCoeffPair& a, const VarCoeffPair& b){
return a < b;
}
};
/**
* ReducedRowVector is a sparse vector representation that represents the
* row as a strictly sorted array of "VarCoeffPair"s.
* The row has a notion of a basic variable.
* This is a variable that must have a coefficient of -1 in the array.
*/
class ReducedRowVector {
public:
typedef std::vector<VarCoeffPair> VarCoeffArray;
typedef VarCoeffArray::const_iterator const_iterator;
private:
typedef std::vector<bool> ArithVarContainsSet;
typedef VarCoeffArray::iterator iterator;
/**
* Invariants:
* - isSorted(d_entries, true)
* - noZeroCoefficients(d_entries)
*/
VarCoeffArray d_entries;
/**
* Buffer for d_entries to reduce allocations by addRowTimesConstant.
*/
VarCoeffArray d_buffer;
/**
* The basic variable associated with the row.
* Must have a coefficient of -1.
*/
ArithVar d_basic;
/**
* Invariants:
* - This set is the same as the set maintained in d_entries.
*/
ArithVarContainsSet d_contains;
std::vector<uint32_t>& d_rowCount;
std::vector<PermissiveBackArithVarSet>& d_columnMatrix;
public:
ReducedRowVector(ArithVar basic,
const std::vector< ArithVar >& variables,
const std::vector< Rational >& coefficients,
std::vector<uint32_t>& count,
std::vector< PermissiveBackArithVarSet >& columnMatrix);
~ReducedRowVector();
void enqueueNonBasicVariablesAndCoefficients(std::vector< ArithVar >& variables,
std::vector< Rational >& coefficients) const;
/** Returns the basic variable.*/
ArithVar basic() const{
Assert(basicIsSet());
return d_basic;
}
/** Returns the number of nonzero variables in the vector. */
uint32_t size() const {
return d_entries.size();
}
/** Iterates over the nonzero entries in the vector. */
const_iterator begin() const { return d_entries.begin(); }
const_iterator end() const { return d_entries.end(); }
/** Returns true if the variable is in the row. */
bool has(ArithVar x_j) const{
if(x_j >= d_contains.size()){
return false;
}else{
return d_contains[x_j];
}
}
/**
* Returns the coefficient of a variable in the row.
*/
const Rational& lookup(ArithVar x_j) const{
Assert(has(x_j));
Assert(hasInEntries(x_j));
const_iterator lb = lower_bound(x_j);
return (*lb).getCoefficient();
}
/** Prints the row to the buffer Debug("row::print"). */
void printRow();
/**
* Changes the basic variable to x_j.
* Precondition: has(x_j)
*/
void pivot(ArithVar x_j);
/**
* Replaces other.basic() in the current row using the other row.
* This assumes the other row represents an equality equal to zero.
*
* \sum(this->entries) -= this->lookup(other.basic()) * (\sum(other.d_entries))
* Precondition:
* has(other.basic())
* basic != other.basic()
*/
void substitute(const ReducedRowVector& other);
/**
* Returns the reduced row as an equality with
* the basic variable on the lhs equal to the sum of the non-basics variables.
* The mapped from ArithVars to Nodes is specificied by map.
*/
Node asEquality(const ArithVarToNodeMap& map) const;
private:
/**
* \sum(this->entries) += c * (\sum(other.d_entries) )
*
* Updates the current row to be the sum of itself and
* another vector times c (c != 0).
*/
void addRowTimesConstant(const Rational& c, const ReducedRowVector& other);
/** Multiplies the coefficients of the RowVector by c (where c != 0). */
void multiply(const Rational& c);
/**
* Adds v to d_contains.
* This may resize d_contains.
*/
static void addArithVar(ArithVarContainsSet& contains, ArithVar v);
/** Removes v from d_contains. */
static void removeArithVar(ArithVarContainsSet& contains, ArithVar v);
/**
* Let c be -1 if strictlySorted is true and c be 0 otherwise.
* isSorted(arr, strictlySorted) is then equivalent to
* If i<j, cmp(getArithVar(d_entries[i]), getArithVar(d_entries[j])) <= c.
*/
static bool isSorted(const VarCoeffArray& arr, bool strictlySorted);
/**
* Zips together an array of variables and coefficients and appends
* it to the end of an output vector.
*/
static void zip(const std::vector< ArithVar >& variables,
const std::vector< Rational >& coefficients,
VarCoeffArray& output);
/**
* Debugging code.
* noZeroCoefficients(arr) is equivalent to
* 0 != getCoefficient(arr[i]) for all i.
*/
static bool noZeroCoefficients(const VarCoeffArray& arr);
/** Debugging code.*/
bool matchingCounts() const;
const_iterator lower_bound(ArithVar x_j) const{
return std::lower_bound(d_entries.begin(), d_entries.end(), VarCoeffPair(x_j, 0));
}
/** Debugging code */
bool wellFormed() const{
return
isSorted(d_entries, true) &&
noZeroCoefficients(d_entries) &&
basicIsSet() &&
has(basic()) &&
lookup(basic()) == Rational(-1);
}
bool basicIsSet() const { return d_basic != ARITHVAR_SENTINEL; }
/** Debugging code. */
bool hasInEntries(ArithVar x_j) const {
return std::binary_search(d_entries.begin(), d_entries.end(), VarCoeffPair(x_j,0));
}
}; /* class ReducedRowVector */
}/* namespace CVC4::theory::arith */
}/* namespace CVC4::theory */
}/* namespace CVC4 */
#endif /* __CVC4__THEORY__ARITH_ARITH_CONSTANTS_H */
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