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/* ========================================================================== */
/* === Source/Mongoose_QPLinks.cpp ========================================== */
/* ========================================================================== */
/* -----------------------------------------------------------------------------
* Mongoose Graph Partitioning Library Copyright (C) 2017-2018,
* Scott P. Kolodziej, Nuri S. Yeralan, Timothy A. Davis, William W. Hager
* Mongoose is licensed under Version 3 of the GNU General Public License.
* Mongoose is also available under other licenses; contact authors for details.
* -------------------------------------------------------------------------- */
#include "Mongoose_QPLinks.hpp"
#include "Mongoose_Debug.hpp"
#include "Mongoose_Internal.hpp"
namespace Mongoose
{
bool QPLinks(EdgeCutProblem *graph, const EdgeCut_Options *options, QPDelta *QP)
{
(void)options; // Unused variable
/* Inputs */
double *x = QP->x;
/* Unpack structures. */
Int n = graph->n;
Int *Ep = graph->p;
Int *Ei = graph->i;
double *Ex = graph->x;
double *a = graph->w;
/* working array */
double *D = QP->D;
Int *FreeSet_status = QP->FreeSet_status;
Int *FreeSet_list = QP->FreeSet_list;
double *grad = QP->gradient; /* gradient at current x */
// FreeSet is empty
Int nFreeSet = 0;
double s = 0.; // a'x
for (Int k = 0; k < n; k++)
{
grad[k] = (0.5 - x[k]) * D[k];
}
for (Int k = 0; k < n; k++)
{
double xk = x[k];
if (xk < 0. || xk > 1.)
{
// Error!
return false;
}
s += ((a) ? a[k] : 1) * xk;
double r = 0.5 - xk;
for (Int p = Ep[k]; p < Ep[k + 1]; p++)
{
grad[Ei[p]] += r * ((Ex) ? Ex[p] : 1);
}
if (xk >= 1.)
{
FreeSet_status[k] = 1;
}
else if (xk <= 0.)
{
FreeSet_status[k] = -1;
}
else
{
// add k to the FreeSet
FreeSet_status[k] = 0;
FreeSet_list[nFreeSet++] = k;
//---
}
}
QP->nFreeSet = nFreeSet;
QP->b = s; // a'x
DEBUG(FreeSet_dump("QPLinks:done", n, FreeSet_list, nFreeSet,
FreeSet_status, 1, x));
// Adjust bounds to force feasibility
if (s > QP->hi)
QP->hi = s;
if (s < QP->lo)
QP->lo = s;
// Note that b can be less than lo or greater than hi.
// b starts between: lo < b < hi
QP->ib = (s <= QP->lo ? -1 : s < QP->hi ? 0 : 1);
#ifndef NDEBUG
// for debugging only
QP->check_cost = INFINITY;
// ib is shorthand for these tests:
Int ib = QP->ib;
PR(("QPlinks: target "
"%g GW %g ib %ld lo %g b %g hi %g b-lo %g hi-b %g\n",
options->target_split, graph->W, ib, QP->lo, QP->b, QP->hi,
(QP->b) - (QP->lo), (QP->hi) - (QP->b)));
fflush(stdout);
fflush(stderr);
double minVal = INFINITY;
double maxVal = 1;
for (Int k = 0; k < n; k++)
{
if (minVal > x[k])
{
minVal = x[k];
}
if (maxVal < x[k])
{
maxVal = x[k];
}
}
minVal = std::max(minVal, 1E-8);
maxVal = std::max(maxVal, 1E-8);
double eps = maxVal * minVal * n;
ASSERT(IMPLIES((ib == -1), (fabs(QP->b - QP->lo) < eps))); // b = lo
ASSERT(IMPLIES((ib == 0), ((QP->lo < (QP->b + eps))
&& (QP->b < (QP->hi + eps))))); // lo < b <hi
ASSERT(IMPLIES((ib == +1), (fabs(QP->b - QP->hi) < eps))); // b = hi
ASSERT((QP->lo <= (QP->b + eps) && QP->b <= (QP->hi + eps))); // x feasible
#endif
return true;
}
} // end namespace Mongoose
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