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////////////////////////////////////////////////////////////////////////////////
//
// LPinterface.cc
//
// produced: 2001/10/28 jr
// last change: 2001/10/28 jr
//
////////////////////////////////////////////////////////////////////////////////
#include "LPinterface.hh"
// constructors:
LPinterface::LPinterface(const Matrix& m, const IntegerSet& support) :
_support(support) {
if (CommandlineOptions::debug()) {
std::cerr << "building LP matrix ..." << std::endl;
}
dd_set_global_constants();
_solver = dd_DualSimplex;
// note that the coefficient matrix m is transposed for efficiency reasons;
_m = m.coldim(); // number of rows
_n = m.rowdim() + 1; // number of cols
_matrixptr = dd_CreateMatrix(_m, _n);
_matrixptr->objective = dd_LPmax;
_matrixptr->numbtype = dd_Rational;
for (size_type i = 0; i < m.coldim(); ++i) {
// build cdd's matrix row by row;
// recall that the coefficient matrix m is transposed for efficiency reasons;
// the first entry is ZERO in every row because
// its meaning in cdd is is "minus the right hand side":
dd_set_R(_matrixptr->matrix[i][0], ZERO);
for (size_type j = 0; j < m.rowdim(); ++j) {
// because the first column contains the data for the right hand side
// (which is ZERO) we need to shift the column index by one;
// again, we have to use the coefficient matrix m in a transposed way:
dd_set_R(_matrixptr->matrix[i][j+1], m(j, i));
}
}
if (CommandlineOptions::debug()) {
dd_WriteMatrix(stderr, _matrixptr);
}
// cdd allows to automatically generate an auxilliary LP for finding an interior point:
dd_LPPtr auxlpptr = dd_Matrix2LP(_matrixptr, &_err);
_lpptr = dd_MakeLPforInteriorFinding(auxlpptr);
if (!_lpptr) {
std::cerr << "error in generating LP." << std::endl;
dd_WriteErrorMessages(stderr, _err);
exit(1);
}
dd_FreeLPData(auxlpptr);
if (CommandlineOptions::debug()) {
std::cerr << "... done." << std::endl;
}
}
// functions:
bool LPinterface::has_interior_point() {
static long idx(0);
// Check feasibility with cdd LP library:
const bool result = dd_LPSolve(_lpptr, _solver, &_err);
if (_err != dd_NoError) {
std::cerr << "error in solving LP." << std::endl;
dd_WriteErrorMessages(stderr, _err);
exit(1);
}
// Write an interior point:
_solptr = dd_CopyLPSolution(_lpptr);
if (dd_Positive(_solptr->optvalue)){
if (CommandlineOptions::output_heights()) {
std::cout << "(";
Field maxheight(ONE);
for (dd_rowrange j = 0; j < (_solptr->d) - 2; j++) {
const Field x_j = Field(_solptr->sol[j+1]);
if (maxheight - 1 < x_j) {
maxheight = x_j + 1;
}
}
for (dd_rowrange j = 0; j < (_solptr->d) - 3; j++) {
const Field x_j = Field(_solptr->sol[j+1]);
if (_support.contains(j)) {
// std::cout << double(x_j);
std::cout << x_j.get_str();
}
else {
if (CommandlineOptions::debug()) {
std::cerr << "point " << j << " unused, assigning height " << maxheight + 1 << std::endl;
}
// std::cout << double(maxheight) + 1;
std::cout << maxheight.get_str();
}
std::cout << ",";
}
const long j((_solptr->d) - 3);
const Field x_j = Field(_solptr->sol[j+1]);
if (_support.contains(j)) {
// std::cout << double(x_j);
std::cout << x_j.get_str();
}
else {
if (CommandlineOptions::debug()) {
std::cerr << "point " << j << " unused, assigning height " << maxheight + 1 << std::endl;
}
// std::cout << double(maxheight) + 1;
std::cout << maxheight.get_str();
}
std::cout << ")" << std::endl;
if (CommandlineOptions::debug()) {
std::cerr << "Used points: " << _support << std::endl;
std::cerr << "Optimal slack: ";
dd_WriteNumber(stderr, _solptr->optvalue);
std::cerr << std::endl;
}
}
if (CommandlineOptions::debug()) {
std::cerr << "... done." << std::endl;
}
return true;
}
if (dd_Negative(_solptr->optvalue)) {
if (CommandlineOptions::debug()) {
std::cerr << "The feasible region is empty." << std::endl;
}
if (CommandlineOptions::debug()) {
std::cerr << "... done." << std::endl;
}
return false;
}
if (dd_EqualToZero(_solptr->optvalue)) {
if (CommandlineOptions::debug()) {
std::cerr << "... done." << std::endl;
}
if (CommandlineOptions::debug()) {
std::cerr << "The feasible region is nonempty but has no interior point." << std::endl;
}
return false;
}
if (CommandlineOptions::debug()) {
std::cerr << "WARNING: unspecified case. I assume that no interior point exists." << std::endl;
}
return false;
}
// eof LPinterface.cc
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