src/ell/StateAcceptor.cc

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00001 #include "ell/StateAcceptor.hh"
00002 #include "biu/RandomNumberFactory.hh" // for SA_Metropolis
00003 #include <cmath> // exp for SA_Metropolis
00004 
00005 
00006 namespace ell {
00007 
00008     bool
00009     SA_All::accept(const StateCollector* const sc, const State& succ) const
00010     {
00011         return true;
00012     }
00013     
00014     
00015     bool
00016     SA_Le::accept(const StateCollector* const sc, const State& succ) const
00017     {
00018         return succ.operator<(*(sc->getLastAdded()));
00019     }
00020     
00021     bool
00022     SA_E_Eq::accept(const StateCollector* const sc, const State& succ) const
00023     {
00024         return ( succ.getEnergy() == sc->getLastAdded()->getEnergy());
00025     }
00026     
00027     bool
00028     SA_E_Gr::accept(const StateCollector* const sc, const State& succ) const
00029     {
00030         return ( succ.getEnergy() > sc->getLastAdded()->getEnergy());
00031     }
00032     
00033     bool
00034     SA_E_GrEq::accept(const StateCollector* const sc, const State& succ) const
00035     {
00036         return ( succ.getEnergy() >= sc->getLastAdded()->getEnergy());
00037     }
00038     
00039     bool
00040     SA_E_Le::accept(const StateCollector* const sc, const State& succ) const
00041     {
00042         return ( succ.getEnergy() < sc->getLastAdded()->getEnergy());
00043     }
00044     
00045     bool
00046     SA_E_LeEq::accept(const StateCollector* const sc, const State& succ) const
00047     {
00048         return ( succ.getEnergy() <= sc->getLastAdded()->getEnergy());
00049     }
00050     
00051     SA_Max_E::SA_Max_E( const double MaxEnergy) : MAX_ENERGY(MaxEnergy) {}
00052     bool
00053     SA_Max_E::accept(const StateCollector* const sc, const State& succ) const
00054     {
00055         return ( succ.getEnergy() <= MAX_ENERGY);
00056     }
00057     
00058     
00059     SA_Metropolis::SA_Metropolis(const double _kT) : kT(_kT) {}
00060     
00061     bool
00062     SA_Metropolis::accept(const StateCollector* const sc, const State& succ) const
00063     {   
00064         // compute energy difference
00065         double deltaE = succ.getEnergy() - sc->getLastAdded()->getEnergy();
00066           // check if negative energy difference --> always accept
00067         if (deltaE < 0)
00068             return true;
00069         // compute probability for accepting state -> Metropolis
00070         double p_accept = exp( - deltaE / kT);
00071         
00072         // compute random number 0 <= r <= 1
00073         double r = (((double) biu::RNF::getRN()) / ((double) biu::RNF::getMaxRN())); 
00074     
00075         // return true with probability p_accept
00076         if ( r < p_accept ) return true;
00077         else return false;
00078     }
00079 
00080 } // namespace ell