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128 lines
4.3 KiB
128 lines
4.3 KiB
/*****************************************************************
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Copyright (c) 2005 Fred Schaettgen <kde.sch@ttgen.net>
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in
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all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
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AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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******************************************************************/
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#ifndef __popularity_h__
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#define __popularity_h__
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#include <qstring.h>
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#include <qstringlist.h>
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class PopularityStatisticsImpl;
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class Prefs;
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/**
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* Tracks the usage of any kind of service to offer recommendations.
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* A service is identified by a string. After calling @useService
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* a few times, you can get a popularity ranking for the used
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* services.
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* The algorithm tries to take both short- and long-term usage
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* into account at the same time.
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* The popularity value can be interpreted as the probability
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* that the given service will be the next one to be used.
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* If some new services are suddenly used a few times, their ranking
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* may grow higher than the ranking of services, which were used very
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* frequently a while ago. But after this short term usage has
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* stopped, its influence gets weaker more quickly then for the old,
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* more frequently used services.
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* During first time usage, the algorithm needs some time to stabilize,
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* since there is simply no dependable long term usage data available,
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* so the ranking is more likely to change at first.
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* But in the long run, the behaviour of the algorithm is
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* completely stable, unlike simple usage counting for instance.
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*/
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class PopularityStatistics
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{
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public:
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PopularityStatistics();
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virtual ~PopularityStatistics();
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/**
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* Touch a service. This will increase the usage
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* counters for the given service and decrease the
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* counters for all the others.
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*/
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void useService(const QString& service);
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/**
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* Exchange all state variables of the most
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* popular service with those from services,
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* moving the given services to the top of the
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* list. Apart from that the order stays the same
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* as before. Order of items in the string list
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* does *not* matter/
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*/
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void moveToTop(const QStringList& services);
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/**
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* Sets all counters to zero for the given service
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*/
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void moveToBottom(const QString& service);
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/**
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* Retrieve the name of a service by its position
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* in the current popularity ranking
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*/
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QString serviceByRank(int n) const;
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/**
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* Retrieve the popularity (0-1) of a service by
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* its position in the current popularity ranking
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*/
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double popularityByRank(int n) const;
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/**
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* Gets the rank of a given service.
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* Returns -1 if the service is not in the ranking
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*/
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int rankByService(const QString service);
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/**
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* Writes the configuration.
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* A section must be set already for config.
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*/
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void writeConfig(Prefs* prefs) const;
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/**
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* Reads the configuration.
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* A section must be set already for config.
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*/
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void readConfig(Prefs* prefs);
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/**
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* Modify the weighting of the history logs.
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* 0 <= h <= 1. 1 means long term history
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* 0 means short term history - in fact the popularity ranking
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* becomes a recently-used list in that case.
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*/
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void setHistoryHorizon(double h);
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double historyHorizon();
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protected:
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PopularityStatisticsImpl *d;
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private:
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PopularityStatistics(const PopularityStatistics&) {}
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};
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#endif
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