c     user amplitude subroutine
      Subroutine vuamp(
C          passed in for information and state variables
     *     ampName, time, ampValueOld, dt, nprops, props, nSvars, svars, 
     *     lFlagsInfo, nSensor, sensorValues, sensorNames, 
     *     jSensorLookUpTable, 
C          to be defined
     *     ampValueNew, 
     *     lFlagsDefine,
     *     AmpDerivative, AmpSecDerivative, AmpIncIntegral)
      
      include 'vaba_param.inc'

C     svars - additional state variables, similar to (V)UEL
      dimension sensorValues(nSensor), svars(nSvars)
      dimension props(nprops)
      character*80 sensorNames(nSensor)
      character*80 ampName

C     time indices
      parameter (iStepTime        = 1,
     *           iTotalTime       = 2,
     *           nTime            = 2)
C     flags passed in for information
      parameter (iInitialization   = 1,
     *           iRegularInc       = 2,
     *           nFlagsInfo        = 2)
C     optional flags to be defined
      parameter (iComputeDeriv     = 1,
     *           iComputeSecDeriv  = 2,
     *           iComputeInteg     = 3,
     *           iStopAnalysis     = 4,
     *           nFlagsDefine      = 4)
      parameter (one = 1.d0)
      dimension time(nTime), lFlagsInfo(nFlagsInfo),
     *          lFlagsDefine(nFlagsDefine)
      dimension jSensorLookUpTable(*)

C     User code to compute  ampValue = F(sensors)
      lFlagsDefine(iComputeDeriv)    = 1
      lFlagsDefine(iComputeSecDeriv) = 0
      lFlagsDefine(iComputeInteg)    = 0

      if (ampName(1:8) .eq. 'LOADAMP2' ) then
         if (lFlagsInfo(iInitialization).eq.1) then 
            ampValueNew      = ampValueOld
            svars(1)         = 0.0
            AmpDerivative = one
         else 
c           Example: f(t) = t
            tim = time(iStepTime)
            tStart = tim - dt
            tEnd   = tim 
            svars(1) = svars(1) + dt
            ampValueNew      = svars(1)
            AmpDerivative = one
c            ampValueNew      = tim

C           stop the analysis, if desired
            if (ampValueNew.gt.1000) lFlagsDefine(iStopAnalysis)=1
         end if
      else if (ampName(1:7) .eq. 'LOADAMP' ) then
         if (lFlagsInfo(iInitialization).eq.1) then 
            ampValueNew      = ampValueOld
            svars(1)         = 0.0
            AmpDerivative = one
         else 
c           Example: f(t) = t
            tim = time(iStepTime)
            tStart = tim - dt
            tEnd   = tim 
            svars(1) = svars(1) + dt
c           state variable with index 2 not used; updated only for 
c           iluustrative purposes
            svars(2) = svars(2) + dt            
            ampValueNew      = svars(1) 
            AmpDerivative = one
c            ampValueNew      = tim

C           stop the analysis, if desired
            if (ampValueNew.gt.1000) lFlagsDefine(iStopAnalysis)=1
         end if
      end if 

      return
      end