/** node selection method of node selector */
static
SCIP_DECL_NODESELSELECT(nodeselSelectBreadthfirst)
{ /*lint --e{715}*/
assert(nodesel != NULL);
assert(strcmp(SCIPnodeselGetName(nodesel), NODESEL_NAME) == 0);
assert(scip != NULL);
assert(selnode != NULL);
/* siblings come before leaves at the same level. Sometimes it can occur that no leaves are left except for children */
*selnode = SCIPgetBestSibling(scip);
if( *selnode == NULL )
{
*selnode = SCIPgetBestLeaf(scip);
if( *selnode == NULL )
*selnode=SCIPgetBestChild(scip);
}
if( *selnode != NULL )
{
SCIPdebugMessage("Selecting next node number %"SCIP_LONGINT_FORMAT" at depth %d\n", SCIPnodeGetNumber(*selnode), SCIPnodeGetDepth(*selnode));
}
return SCIP_OKAY;
}
/** node selection method of node selector */
static
SCIP_DECL_NODESELSELECT(nodeselSelectBfs)
{ /*lint --e{715}*/
SCIP_NODESELDATA* nodeseldata;
int minplungedepth;
int maxplungedepth;
int plungedepth;
SCIP_Real maxplungequot;
assert(nodesel != NULL);
assert(strcmp(SCIPnodeselGetName(nodesel), NODESEL_NAME) == 0);
assert(scip != NULL);
assert(selnode != NULL);
*selnode = NULL;
/* get node selector user data */
nodeseldata = SCIPnodeselGetData(nodesel);
assert(nodeseldata != NULL);
/* calculate minimal and maximal plunging depth */
minplungedepth = nodeseldata->minplungedepth;
maxplungedepth = nodeseldata->maxplungedepth;
maxplungequot = nodeseldata->maxplungequot;
if( minplungedepth == -1 )
{
minplungedepth = SCIPgetMaxDepth(scip)/10;
if( SCIPgetNStrongbranchLPIterations(scip) > 2*SCIPgetNNodeLPIterations(scip) )
minplungedepth += 10;
if( maxplungedepth >= 0 )
minplungedepth = MIN(minplungedepth, maxplungedepth);
}
if( maxplungedepth == -1 )
maxplungedepth = SCIPgetMaxDepth(scip)/2;
maxplungedepth = MAX(maxplungedepth, minplungedepth);
/* check, if we exceeded the maximal plunging depth */
plungedepth = SCIPgetPlungeDepth(scip);
if( plungedepth > maxplungedepth )
{
/* we don't want to plunge again: select best node from the tree */
SCIPdebugMessage("plungedepth: [%d,%d], cur: %d -> abort plunging\n", minplungedepth, maxplungedepth, plungedepth);
*selnode = SCIPgetBestNode(scip);
SCIPdebugMessage(" -> best node : lower=%g\n",
*selnode != NULL ? SCIPnodeGetLowerbound(*selnode) : SCIPinfinity(scip));
}
else
{
SCIP_NODE* node;
SCIP_Real maxbound;
/* check, if plunging is forced at the current depth */
if( plungedepth < minplungedepth )
{
maxbound = SCIPinfinity(scip);
SCIPdebugMessage("plungedepth: [%d,%d], cur: %d => maxbound: infinity\n",
minplungedepth, maxplungedepth, plungedepth);
}
else
{
SCIP_Real lowerbound;
SCIP_Real cutoffbound;
/* get global lower and cutoff bound */
lowerbound = SCIPgetLowerbound(scip);
cutoffbound = SCIPgetCutoffbound(scip);
/* if we didn't find a solution yet, the cutoff bound is usually very bad:
* use only 20% of the gap as cutoff bound
*/
if( SCIPgetNSolsFound(scip) == 0 )
cutoffbound = lowerbound + 0.2 * (cutoffbound - lowerbound);
/* calculate maximal plunging bound */
maxbound = lowerbound + maxplungequot * (cutoffbound - lowerbound);
SCIPdebugMessage("plungedepth: [%d,%d], cur: %d, bounds: [%g,%g], maxbound: %g\n",
minplungedepth, maxplungedepth, plungedepth, lowerbound, cutoffbound, maxbound);
}
/* we want to plunge again: prefer children over siblings, and siblings over leaves,
* but only select a child or sibling, if its dual bound is small enough;
* prefer using nodes with higher node selection priority assigned by the branching rule
*/
node = SCIPgetPrioChild(scip);
if( node != NULL && SCIPnodeGetLowerbound(node) < maxbound )
{
*selnode = node;
SCIPdebugMessage(" -> selected prio child: lower=%g\n", SCIPnodeGetLowerbound(*selnode));
}
else
{
node = SCIPgetBestChild(scip);
if( node != NULL && SCIPnodeGetLowerbound(node) < maxbound )
{
*selnode = node;
SCIPdebugMessage(" -> selected best child: lower=%g\n", SCIPnodeGetLowerbound(*selnode));
}
else
{
node = SCIPgetPrioSibling(scip);
if( node != NULL && SCIPnodeGetLowerbound(node) < maxbound )
{
*selnode = node;
SCIPdebugMessage(" -> selected prio sibling: lower=%g\n", SCIPnodeGetLowerbound(*selnode));
}
else
{
node = SCIPgetBestSibling(scip);
if( node != NULL && SCIPnodeGetLowerbound(node) < maxbound )
{
*selnode = node;
SCIPdebugMessage(" -> selected best sibling: lower=%g\n", SCIPnodeGetLowerbound(*selnode));
}
else
{
*selnode = SCIPgetBestNode(scip);
SCIPdebugMessage(" -> selected best leaf: lower=%g\n",
*selnode != NULL ? SCIPnodeGetLowerbound(*selnode) : SCIPinfinity(scip));
}
}
}
}
}
return SCIP_OKAY;
}
