subroutine sddir_precalc
c Applying velocity Verlet algorithm - step 1 to coordinates        
      implicit real*8 (a-h,o-z)
      include 'DIMENSIONS'
      include 'COMMON.CONTROL'
      include 'COMMON.VAR'
      include 'COMMON.MD'
      include 'COMMON.LANGEVIN'
      include 'COMMON.CHAIN'
      include 'COMMON.DERIV'
      include 'COMMON.GEO'
      include 'COMMON.LOCAL'
      include 'COMMON.INTERACT'
      include 'COMMON.IOUNITS'
      include 'COMMON.NAMES'
      double precision stochforcvec(MAXRES6)
      common /stochcalc/ stochforcvec
c
c Compute friction and stochastic forces
c
      call friction_force
      call stochastic_force(stochforcvec) 
c
c Compute the acceleration due to friction forces (d_af_work) and stochastic
c forces (d_as_work)
c
      do i=1,dimen
        d_af_work(i)=0.0d0
        d_as_work(i)=0.0d0
        do j=1,dimen
          d_af_work(i)=d_af_work(i)+Ginv(i,j)*fric_work(j)
          d_as_work(i)=d_as_work(i)+Ginv(i,j)*stochforcvec(j)
        enddo
      enddo
      return
      end