351 lines
8.3 KiB
C++
351 lines
8.3 KiB
C++
/*
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----
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This file is part of SECONDO.
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Copyright (C) 2020,
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Faculty of Mathematics and Computer Science,
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Database Systems for New Applications.
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SECONDO is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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SECONDO is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with SECONDO; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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----
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This files realizes a balanced dsitribution of slots to workers.
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*/
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#include "BalancedCollect.h"
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#include <string>
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#include <iostream>
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#include <vector>
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#include <sstream>
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#include <algorithm>
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#include <queue>
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#include <assert.h>
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using namespace std;
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namespace distributed2 {
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namespace loadbalance {
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/*
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~class Slot~
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A slot is represented by its number and the size.
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*/
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class Slot{
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public:
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Slot(size_t _no, double _size): no(_no), size(_size) {}
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size_t getNo() const { return no; }
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double getSize() const { return size;}
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string toString() const{
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stringstream ss;
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ss << no <<"(" << size << ")";
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return ss.str();
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}
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static bool sizeGreater(const Slot& s1, const Slot& s2) {
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return s1.size > s2.size;
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}
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private:
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size_t no;
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double size;
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};
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std::ostream& operator<<(ostream& o, const Slot& s){
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return o << s.toString();
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}
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/*
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Class representing a DWorker.
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A DWorker is represented as a vector of Slots
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contained by this worker.
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*/
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class DWorker{
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public:
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DWorker(int _no) : no(_no),size(0) {}
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void add (Slot slot){
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slots.push_back(slot);
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size += slot.getSize();
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}
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Slot removeTop(){
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if(slots.empty()) return Slot(-1,-1);
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Slot res = slots.back();
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slots.pop_back();
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size -= res.getSize();
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return res;
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}
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string toString() const{
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stringstream ss;
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for(size_t i=0;i<slots.size(); i++){
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if( i > 0) ss << " + " ;
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ss << slots[i].toString();
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}
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ss << " => " << size ;
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return ss.str();
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}
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string sizeString() const{
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stringstream ss;
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for(size_t i=0;i<slots.size(); i++){
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if( i > 0) ss << " + " ;
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ss << slots[i].getSize();
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}
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ss << " => " << size ;
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return ss.str();
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}
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size_t getNoSlots() const { return slots.size(); }
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double getNoElements() const { return size; }
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size_t getId () const{ return no; }
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const vector<Slot>& getSlots() const { return slots; }
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private:
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size_t no; // identifikator of this worker
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double size; // summarized size of all slots
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vector<Slot> slots;
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};
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/*
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~wless~
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Comparator for DWorkers.
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Returns true if the left DWorker has more elements than the right one.
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*/
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class wless {
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public:
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bool operator()(const DWorker& left, const DWorker& right){
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return left.getNoElements()< right.getNoElements();
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}
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};
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class wgreater{
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public:
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bool operator()(const DWorker& left, const DWorker& right){
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return left.getNoElements() > right.getNoElements();
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}
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};
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/*
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~SimpleDist~
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Implementation of a Distributor.
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Slots are sorted by decreasinge size.
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Then it iteratet over the sorted slots. The next slot is assigned to
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that DWorker having the smallest amount of elements.
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*/
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class Distributor{
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public:
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vector<DWorker> distributeSimple(vector<Slot>& slots,
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int noDWorkers) {
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return distribute(slots, noDWorkers, 0);
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}
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vector<DWorker> distributeComplete(vector<Slot>& slots,
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int noDWorkers){
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return distribute(slots, noDWorkers, getNoReserve(noDWorkers));
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}
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private :
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virtual vector<DWorker> distribute(vector<Slot>& slots,
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int noDWorkers,
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int noReserve) {
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// sort slots in descending order
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sort(slots.begin(), slots.end(), Slot::sizeGreater);
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// create completely empty dworkers (full set)
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DWorkers.clear();
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for(int i=0;i<noDWorkers;i++){
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DWorker w(i);
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DWorkers.push_back(w);
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}
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// insert the first workers into a prio queue
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priority_queue<DWorker, vector<DWorker>, wgreater> q;
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for(size_t i=0;i<DWorkers.size()-noReserve; i++){
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q.push(DWorkers[i]);
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}
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// distribute the slot over the available workers in
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// descending order
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completeSize = 0;
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for(size_t i=0;i<slots.size(); i++){
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Slot slot = slots[i];
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completeSize += slot.getSize();
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DWorker w = q.top();
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q.pop();
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w.add(slot);
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q.push(w);
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}
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// write back the result
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while(!q.empty() ){
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DWorker w = q.top();
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q.pop();
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DWorkers[w.getId()] = w;
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}
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if(noReserve > 0){
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reDistribute(noReserve);
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}
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return DWorkers;
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};
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vector<DWorker> DWorkers; // the workers
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double completeSize; // size of the whole relation
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// 5 percent
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uint32_t getNoReserve(int noWorkers){
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if(noWorkers < 4){
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return 0;
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}
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return ((uint32_t) ((noWorkers-1)*0.05))+1;
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}
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void reDistribute(uint32_t noReserve){
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double avgSize = completeSize / DWorkers.size();
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double maxSize = 1.03 * avgSize;
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priority_queue<DWorker, vector<DWorker>, wgreater> qreserve;
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for(size_t i=DWorkers.size()-noReserve; i< DWorkers.size();i++){
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DWorker w = DWorkers[i];
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qreserve.push(w);
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}
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priority_queue<DWorker, vector<DWorker>, wless> qbase;
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for(size_t i=0;i<DWorkers.size()-noReserve; i++){
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DWorker w = DWorkers[i];
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qbase.push(w);
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}
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while(!qbase.empty()){
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DWorker w = qbase.top(); // the highest worker
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qbase.pop();
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DWorker r = qreserve.top(); // the smallest reserve
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qreserve.pop();
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if(exchange(w,r,maxSize)){
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qbase.push(w);
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} else {
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DWorkers[w.getId()] = w; // fix result
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}
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qreserve.push(r);
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}
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/*
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// variant 2
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vector<DWorker> qbase;
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for(size_t i=0;i<DWorkers.size()-noReserve; i++){
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DWorker w = DWorkers[i];
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qbase.push_back(w);
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}
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bool change = true;
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while(change){
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change = false;
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for(size_t i=0;i<qbase.size();i++){
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DWorker r = qreserve.top();
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qreserve.pop();
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DWorker w = qbase[i];
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change |= exchange(w,r,maxSize);
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qreserve.push(r);
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}
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}
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*/
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// fix reserve
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while(!qreserve.empty()){
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DWorker w = qreserve.top();
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qreserve.pop();
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DWorkers[w.getId()] = w;
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}
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}
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bool exchange(DWorker& source, DWorker& target, double maxSize){
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if(source.getNoSlots() < 2){
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return false;
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}
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Slot slot = source.removeTop();
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double ts = target.getNoElements();
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if(ts + slot.getSize() > maxSize){
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source.add(slot);
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return false;
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} else {
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target.add(slot);
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return true;
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}
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}
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};
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/*
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Returns a vektor having the size slotsizes.
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The content of each field is the assigned worker.
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*/
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vector<uint32_t> getMapping(const vector<double>& slotsizes,
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uint32_t noWorkers,
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bool simple) {
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vector<Slot> slots;
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vector<uint32_t> result;
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for(size_t i=0;i<slotsizes.size();i++){
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slots.push_back(Slot(i,slotsizes[i]));
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result.push_back(0); // will be overwritten later
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}
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Distributor dist;
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vector<DWorker> worker =
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simple ? dist.distributeSimple(slots,noWorkers)
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: dist.distributeComplete(slots,noWorkers);
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for(auto w : worker){
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size_t wn = w.getId();
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for(auto& s : w.getSlots()){
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result[s.getNo()] = wn;
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}
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}
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return result;
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}
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} // end of namespace loadbalance
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}
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