ExponentialDecaySpikeResponse.h

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#ifndef EXPONENTIALDECAYSPIKERESPONSE_H_
#define EXPONENTIALDECAYSPIKERESPONSE_H_

#include "PCSIMException.h"
#include "FiniteSpikeResponse.h"

class ExponentialDecaySpikeResponse : public FiniteSpikeResponse
{

        SIMOBJECT ( ExponentialDecaySpikeResponse, AdvancePhase::SpikeDriven )

public:
    ExponentialDecaySpikeResponse(
        const float tau=3e-3
    ): FiniteSpikeResponse(), tau(tau)
    { /* NOOP */ };

    virtual ~ExponentialDecaySpikeResponse()
    { /* NOOP */ };


    float tau;

    // Update internal variables
    virtual int adjust( double dt );

    // Reset to initial condition.
    virtual int reset( double dt );

    virtual int advance(AdvanceInfo const & );

    virtual int spikeHit( spikeport_t port, SpikeEvent const& spike );


    virtual int psrLength(double dt) const;

private:
    double decay;

};

inline int ExponentialDecaySpikeResponse::adjust( double dt )
{
    if ( tau > 0 )
        decay = exp( - dt / tau );
    else {
        throw( PCSIM::Exception( "ExponentialDecaySpikeResponse::adjust", "Time constant not a positive vlaue!" ) );
    }
    return 0;
}

inline int ExponentialDecaySpikeResponse::reset( double dt )
{
    FiniteSpikeResponse::reset( dt );
    adjust( dt );
    return 0;
}

inline int ExponentialDecaySpikeResponse::advance(AdvanceInfo const &)
{
    // Do the exponantial decay
    psr *= decay;
    return advanceReturn();
}

inline int ExponentialDecaySpikeResponse::spikeHit( spikeport_t port, SpikeEvent const& spike )
{
    // 3.) Add weight to psr as if spike had occured at time t and has amplitude weight at time ts    
    psr += spike.weight / exp( - spike.delta / tau );
     
    return spikeHitReturn( AdvanceInfo( spike.dt ) );
}

inline int ExponentialDecaySpikeResponse::psrLength(double dt) const
{
    return (int)( (double)PSR_MULTIPLE_TAU * tau / dt + 0.5 );
}

#endif /*EXPONENTIALDECAYSPIKERESPONSE_H_*/

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