block.cpp

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#include <cassert>
#include <memory>
#include <vpsc/pairingheap/PairingHeap.h>
#include <vpsc/constraint.h>
#include <vpsc/block.h>
#include <vpsc/blocks.h>
#include <fstream>
using std::ios;
using std::ofstream;
using std::vector;
 
#ifndef RECTANGLE_OVERLAP_LOGGING
        #define RECTANGLE_OVERLAP_LOGGING 0
#endif
 
void Block::addVariable(Variable *v) {
        v->block=this;
        vars.push_back(v);
        weight+=v->weight;
        wposn += v->weight * (v->desiredPosition - v->offset);
        posn=wposn/weight;
}
Block::Block(Variable *v) {
        timeStamp=0;
        posn=weight=wposn=0;
        deleted=false;
        if(v!=nullptr) {
                v->offset=0;
                addVariable(v);
        }
}
 
double Block::desiredWeightedPosition() {
        double wp = 0;
        for (const Variable *v : vars) {
                wp += (v->desiredPosition - v->offset) * v->weight;
        }
        return wp;
}
void Block::setUpInConstraints() {
        setUpConstraintHeap(in,true);
}
void Block::setUpOutConstraints() {
        setUpConstraintHeap(out,false);
}
void Block::setUpConstraintHeap(std::unique_ptr<PairingHeap<Constraint*>> &h,
          bool use_in) {
        h = std::make_unique<PairingHeap<Constraint*>>(&compareConstraints);
        for (Variable *v : vars) {
                vector<Constraint*> *cs= use_in ? &v->in : &v->out;
                for (Constraint *c : *cs) {
                        c->timeStamp=blockTimeCtr;
                        if ((c->left->block != this && use_in) || (c->right->block != this && !use_in)) {
                                h->insert(c);
                        }
                }
        }
}       
void Block::merge(Block* b, Constraint* c) {
        if (RECTANGLE_OVERLAP_LOGGING) {
                ofstream f(LOGFILE,ios::app);
                f<<"  merging on: "<<*c<<",c->left->offset="<<c->left->offset<<",c->right->offset="<<c->right->offset<<"\n";
        }
        const double dist = c->right->offset - c->left->offset - c->gap;
        Block *l=c->left->block;
        Block *r=c->right->block;
        if (vars.size() < b->vars.size()) {
                r->merge(l,c,dist);
        } else {
                l->merge(r,c,-dist);
        }
        if (RECTANGLE_OVERLAP_LOGGING) {
                ofstream f(LOGFILE,ios::app);
                f<<"  merged block="<<(b->deleted?*this:*b)<<"\n";
        }
}
void Block::merge(Block *b, Constraint *c, double dist) {
        if (RECTANGLE_OVERLAP_LOGGING) {
                ofstream f(LOGFILE,ios::app);
                f<<"    merging: "<<*b<<"dist="<<dist<<"\n";
        }
        c->active=true;
        wposn+=b->wposn-dist*b->weight;
        weight+=b->weight;
        posn=wposn/weight;
        for (Variable *v : b->vars) {
                v->block=this;
                v->offset+=dist;
                vars.push_back(v);
        }
        b->deleted=true;
}
 
void Block::mergeIn(Block *b) {
        if (RECTANGLE_OVERLAP_LOGGING) {
                ofstream f(LOGFILE,ios::app);
                f<<"  merging constraint heaps... \n";
        }
        // We check the top of the heaps to remove possible internal constraints
        findMinInConstraint();
        b->findMinInConstraint();
        in->merge(b->in.get());
        if (RECTANGLE_OVERLAP_LOGGING) {
                ofstream f(LOGFILE,ios::app);
                f<<"  merged heap: "<<*in<<"\n";
        }
}
void Block::mergeOut(Block *b) {        
        findMinOutConstraint();
        b->findMinOutConstraint();
        out->merge(b->out.get());
}
Constraint *Block::findMinInConstraint() {
        Constraint *v = nullptr;
        vector<Constraint*> outOfDate;
        while (!in->isEmpty()) {
                v = in->findMin();
                const Block *lb = v->left->block;
                const Block *rb = v->right->block;
                // rb may not be this if called between merge and mergeIn
                if (RECTANGLE_OVERLAP_LOGGING) {
                        ofstream f(LOGFILE,ios::app);
                        f<<"  checking constraint ... "<<*v;
                        f<<"    timestamps: left="<<lb->timeStamp<<" right="<<rb->timeStamp<<" constraint="<<v->timeStamp<<"\n";
                }
                if(lb == rb) {
                        // constraint has been merged into the same block
                        if(RECTANGLE_OVERLAP_LOGGING && v->slack()<0) {
                                ofstream f(LOGFILE,ios::app);
                                f<<"  violated internal constraint found! "<<*v<<"\n";
                                f<<"     lb="<<*lb<<"\n";
                                f<<"     rb="<<*rb<<"\n";
                        }
                        in->deleteMin();
                        if (RECTANGLE_OVERLAP_LOGGING) {
                                ofstream f(LOGFILE,ios::app);
                                f<<" ... skipping internal constraint\n";
                        }
                } else if(v->timeStamp < lb->timeStamp) {
                        // block at other end of constraint has been moved since this
                        in->deleteMin();
                        outOfDate.push_back(v);
                        if (RECTANGLE_OVERLAP_LOGGING) {
                                ofstream f(LOGFILE,ios::app);
                                f<<"    reinserting out of date (reinsert later)\n";
                        }
                } else {
                        break;
                }
        }
        for (Constraint *c : outOfDate) {
                c->timeStamp=blockTimeCtr;
                in->insert(c);
        }
        if(in->isEmpty()) {
                v=nullptr;
        } else {
                v=in->findMin();
        }
        return v;
}
Constraint *Block::findMinOutConstraint() {
        if(out->isEmpty()) return nullptr;
        Constraint *v = out->findMin();
        while (v->left->block == v->right->block) {
                out->deleteMin();
                if(out->isEmpty()) return nullptr;
                v = out->findMin();
        }
        return v;
}
void Block::deleteMinInConstraint() {
        in->deleteMin();
        if (RECTANGLE_OVERLAP_LOGGING) {
                ofstream f(LOGFILE,ios::app);
                f<<"deleteMinInConstraint... \n";
                f<<"  result: "<<*in<<"\n";
        }
}
void Block::deleteMinOutConstraint() {
        out->deleteMin();
}
inline bool Block::canFollowLeft(const Constraint *c, const Variable *last) {
        return c->left->block==this && c->active && last!=c->left;
}
inline bool Block::canFollowRight(const Constraint *c, const Variable *last) {
        return c->right->block==this && c->active && last!=c->right;
}
 
// computes the derivative of v and the lagrange multipliers
// of v's out constraints (as the recursive sum of those below.
// Does not backtrack over u.
// also records the constraint with minimum lagrange multiplier
// in min_lm
double Block::compute_dfdv(Variable *v, Variable *u, Constraint *&min_lm) {
        double dfdv=v->weight*(v->position() - v->desiredPosition);
        for (Constraint *c : v->out) {
                if(canFollowRight(c,u)) {
                        dfdv+=c->lm=compute_dfdv(c->right,v,min_lm);
                        if(min_lm==nullptr||c->lm<min_lm->lm) min_lm=c;
                }
        }
        for (Constraint *c : v->in) {
                if(canFollowLeft(c,u)) {
                        dfdv-=c->lm=-compute_dfdv(c->left,v,min_lm);
                        if(min_lm==nullptr||c->lm<min_lm->lm) min_lm=c;
                }
        }
        return dfdv;
}
 
 
// computes dfdv for each variable and uses the sum of dfdv on either side of
// the constraint c to compute the lagrangian multiplier lm_c.
// The top level v and r are variables between which we want to find the
// constraint with the smallest lm.  
// When we find r we pass nullptr to subsequent recursive calls, 
// thus r=nullptr indicates constraints are not on the shortest path.
// Similarly, m is initially nullptr and is only assigned a value if the next
// variable to be visited is r or if a possible min constraint is returned from
// a nested call (rather than nullptr).
// Then, the search for the m with minimum lm occurs as we return from
// the recursion (checking only constraints traversed left-to-right 
// in order to avoid creating any new violations).
Block::Pair Block::compute_dfdv_between(Variable* r, Variable* v, Variable* u, 
                Direction dir = NONE, bool changedDirection = false) {
        double dfdv=v->weight*(v->position() - v->desiredPosition);
        Constraint *m=nullptr;
        for (Constraint *c : v->in) {
                if(canFollowLeft(c,u)) {
                        if(dir==RIGHT) { 
                                changedDirection = true; 
                        }
                        if(c->left==r) {
                                r=nullptr; m=c; 
                        }
                        Pair p=compute_dfdv_between(r,c->left,v,
                                        LEFT,changedDirection);
                        dfdv -= c->lm = -p.first;
                        if(r && p.second) 
                                m = p.second;
                }
        }
        for (Constraint *c : v->out) {
                if(canFollowRight(c,u)) {
                        if(dir==LEFT) { 
                                changedDirection = true; 
                        }
                        if(c->right==r) {
                                r=nullptr; m=c; 
                        }
                        Pair p=compute_dfdv_between(r,c->right,v,
                                        RIGHT,changedDirection);
                        dfdv += c->lm = p.first;
                        if(r && p.second) 
                                m = changedDirection && c->lm < p.second->lm 
                                        ? c 
                                        : p.second;
                }
        }
        return Pair(dfdv,m);
}
 
// resets LMs for all active constraints to 0 by
// traversing active constraint tree starting from v,
// not back tracking over u
void Block::reset_active_lm(Variable *v, Variable *u) {
        for (Constraint *c : v->out) {
                if(canFollowRight(c,u)) {
                        c->lm=0;
                        reset_active_lm(c->right,v);
                }
        }
        for (Constraint *c : v->in) {
                if(canFollowLeft(c,u)) {
                        c->lm=0;
                        reset_active_lm(c->left,v);
                }
        }
}
Constraint *Block::findMinLM() {
        Constraint *min_lm=nullptr;
        reset_active_lm(vars.front(),nullptr);
        compute_dfdv(vars.front(),nullptr,min_lm);
        return min_lm;
}
Constraint *Block::findMinLMBetween(Variable* lv, Variable* rv) {
        Constraint *min_lm=nullptr;
        reset_active_lm(vars.front(),nullptr);
        min_lm=compute_dfdv_between(rv,lv,nullptr).second;
        return min_lm;
}
 
// populates block b by traversing the active constraint tree adding variables as they're 
// visited.  Starts from variable v and does not backtrack over variable u.
void Block::populateSplitBlock(Block *b, Variable *v, Variable *u) {
        b->addVariable(v);
        for (Constraint *c : v->in) {
                if (canFollowLeft(c,u))
                        populateSplitBlock(b, c->left, v);
        }
        for (Constraint *c : v->out) {
                if (canFollowRight(c,u))
                        populateSplitBlock(b, c->right, v);
        }
}
Constraint* Block::splitBetween(Variable* vl, Variable* vr, Block* &lb, Block* &rb) {
        if (RECTANGLE_OVERLAP_LOGGING) {
                ofstream f(LOGFILE,ios::app);
                f<<"  need to split between: "<<*vl<<" and "<<*vr<<"\n";
        }
        Constraint *c=findMinLMBetween(vl, vr);
        if (RECTANGLE_OVERLAP_LOGGING) {
                ofstream f(LOGFILE,ios::app);
                f<<"  going to split on: "<<*c<<"\n";
        }
        split(lb,rb,c);
        deleted = true;
        return c;
}
void Block::split(Block* &l, Block* &r, Constraint* c) {
        c->active=false;
        l=new Block();
        populateSplitBlock(l,c->left,c->right);
        r=new Block();
        populateSplitBlock(r,c->right,c->left);
}
 
double Block::cost() {
        double c = 0;
        for (const Variable *v : vars) {
                const double diff = v->position() - v->desiredPosition;
                c += v->weight * diff * diff;
        }
        return c;
}
ostream& operator <<(ostream &os, const Block &b)
{
        os<<"Block:";
        for(const Variable *v : b.vars) {
                os<<" "<<*v;
        }
        if(b.deleted) {
                os<<" Deleted!";
        }
    return os;
}