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- c*******************************************************************
- c TU4_LDRIFT_TP.F
- c*********************************************************************
- c LDRIFT gives a 'linear drift' to the bary. positions for use in
- c the symplectic code based on Ham. of the form T(p) + V(x).
- c TEST PARTICLES
- c
- c Input:
- c ntp ==> number of bodies (int scalar)
- c xbt,ybt,zbt ==> initial position in beri coord
- c (real arrays)
- c vxbt,vybt,vzbt ==> initial velocity in beri coord
- c (real arrays)
- c dt ==> time step
- c istat ==> status of the test paricles
- c (integer array)
- c istat(i) = 0 ==> active: = 1 not
- c NOTE: it is really a 2d array but
- c we only use the 1st row
- c Output:
- c xbt,ybt,zbt ==> final position in beri coord
- c (real arrays)
- c vxbt,vybt,vzbt ==> final velocity in beri coord
- c (real arrays)
- c
- c Remarks: Based on Martin's NB4M routines
- c Authors: Martin Duncan
- c Date: 3/8/93
- c Last revision:
- subroutine tu4_ldrift_tp(ntp,xbt,ybt,zbt,vxbt,vybt,vzbt,
- & dt,istat)
- include '../swift.inc'
- c... Inputs Only:
- integer ntp,istat(ntp)
- real*8 dt
- c... Inputs and Outputs:
- real*8 xbt(ntp),ybt(ntp),zbt(ntp)
- real*8 vxbt(ntp),vybt(ntp),vzbt(ntp)
- c... Internals
- integer i
- c---
- c... Executable code
- do i=1,ntp
- if(istat(i).eq.0) then
- xbt(i) = xbt(i) + vxbt(i)*dt
- ybt(i) = ybt(i) + vybt(i)*dt
- zbt(i) = zbt(i) + vzbt(i)*dt
- endif
- enddo
- return
- end ! tu4_ldrift_tp
- c____________________________________________________________________________
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