anchor.diff:  
   !    Simulation parameters
   
  -real(wp), parameter :: endTime=100.0e-3_wp ! simulation ends (seconds)
  +real(wp), parameter :: endTime=100e-7_wp !100.0e-3_wp ! simulation ends (seconds)
   real(wp), parameter :: Tstep=0.5e-7_wp ! simulation time steps
   integer, parameter :: TT= floor(endTime / Tstep)              ! floor(endTime/Tstep)+2;
   integer, parameter :: res=20
  
positive.code:       cte1=1.5*omegae*(lambdaD*k(pp))*(lambdaD*k(pp))
  			!cte1=1.5*Kb*Te/me/omega_off*k(pp)*k(pp)-(pow(omega_off,2)-pow(omegae,2))/2.0/omega_off;
        k4(pp,1)=Tstep*(cte1*(EE(c1,pp,2)+k3(pp,2)-SSE(pp,1)*Tstep)-nuE(pp)*(EE(c1,pp,1)+k3(pp,1)+SSE(pp,2)*Tstep)+cte2*CC(2));
        k4(pp,2)=Tstep*((-1)*cte1*(EE(c1,pp,1)+k3(pp,1)+SSE(pp,2)*Tstep)-nuE(pp)*(EE(c1,pp,2)+k3(pp,2)-SSE(pp,1)*Tstep)-cte2*CC(1));
  
        EE(c2,pp,1)=EE(c1,pp,1)+(k1(pp,1)+2.0*k2(pp,1)+2.0*k3(pp,1)+k4(pp,1))/6.0+SSE(pp,2)*Tstep
        EE(c2,pp,2)=EE(c1,pp,2)+(k1(pp,2)+2.0*k2(pp,2)+2.0*k3(pp,2)+k4(pp,2))/6.0-SSE(pp,1)*Tstep
        EE(c2,N/2,:)=0.0_wp
  
  
  
negative.code: 
  
  real(wp):: EE(3,N,2), nn(3,N,2), vv(3,N,2), CC(2), SSE(N,2), SSn(2), cte1, cte2, &
      k1(N,2), k2(N,2), k3(N,2), k4(N,2), kn1(2), kn2(2), kn3(2), kn4(2), kv1(2), kv2(2), kv3(2), kv4(2)
  
  integer :: LL,UU,pp
  
  