xcpred.f

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      SUBROUTINE xcpred(KCASE)
*
*
*       Prediction of global chain coordinates.
*       ---------------------------------------
*
      include 'common6.h'
      REAL*8  m,mass,mc,mij,mkk
      parameter(nmx=10,nmx3=3*nmx,nmxm=nmx*(nmx-1)/2)
      common/chain1/  xch(nmx3),vch(nmx3),m(nmx),
     &                zz(nmx3),wc(nmx3),mc(nmx),
     &                xi(nmx3),pi(nmx3),mass,rinv(nmxm),rsum,mkk(nmx),
     &                mij(nmx,nmx),tkk(nmx),tk1(nmx),iname(nmx),nn
      common/chainc/  xc(3,ncmax),uc(3,ncmax),bodyc(ncmax),ich,
     &                listc(lmax)
*
*
*       Check indicator for prediction of perturbers & c.m.
      IF (kcase.EQ.0) go to 4
*
*       Check adding chain c.m. #ICH to perturber list for prediction.
      IF (kcase.EQ.1) THEN
          nnb2 = listc(1) + 2
          listc(nnb2) = ich
      ELSE
*      Note KCASE = 2 for chain c.m. prediction at new block-time.
          nnb2 = listc(1) + 1
      END IF
*
*       Predict X & XDOT of perturbers and (if needed) c.m. to order FDOT.
      DO 1 l = 2,nnb2
          j = listc(l)
          s = time - t0(j)
          s1 = 1.5*s
          s2 = 2.0*s
*       Note no bad effects in DIFSY1 for prediction outside range.
*         S = MIN(S,STEP(J))
          x(1,j) = ((fdot(1,j)*s + f(1,j))*s + x0dot(1,j))*s + x0(1,j)
          x(2,j) = ((fdot(2,j)*s + f(2,j))*s + x0dot(2,j))*s + x0(2,j)
          x(3,j) = ((fdot(3,j)*s + f(3,j))*s + x0dot(3,j))*s + x0(3,j)
          xdot(1,j) = (fdot(1,j)*s1 + f(1,j))*s2 + x0dot(1,j)
          xdot(2,j) = (fdot(2,j)*s1 + f(2,j))*s2 + x0dot(2,j)
          xdot(3,j) = (fdot(3,j)*s1 + f(3,j))*s2 + x0dot(3,j)
    1 CONTINUE
*
*       Obtain global coordinates & velocities from current chain & c.m.
   4  lk = 0
      DO 10 i = 1,nn
          DO 5 k = 1,3
              lk = lk + 1
              xc(k,i) = xch(lk) + x(k,ich)
              uc(k,i) = vch(lk) + xdot(k,ich)
    5     CONTINUE
   10 CONTINUE
*
      RETURN
*
      END