C DVINVE    SOURCE    CB215821  26/08/24    21:16:19     12622          
      subroutine dvinve(md,tens,v,x,inv)
c
c     *********
c     inversion
c     *********
c
      implicit real*8(a-h,o-z)
      implicit integer (i-n)
      real*8 v(5),x(5),tens(5,5)
 1000 continue
      do 1600 iy=1,md-1
 1005 continue
      if(tens(iy,iy).eq.0.) go to 1030
      do 1020 iz=iy+1,md
      do 1010 iw=iy+1,md
      tens(iz,iw)=tens(iz,iw)-tens(iz,iy)*tens(iy,iw)/tens(iy,iy)
 1010 CONTINUE
      v(iz)=v(iz) - tens(iz,iy)*v(iy)/tens(iy,iy)
 1020 CONTINUE
      go to 1600
 1030 continue
      indic3=0
      if(iy.eq.md) go to 1600
      do 1500 iz=iy+1,md
      if(tens(iz,iy).eq.0.) go to 1500
      if(indic3.eq.1) go to 1500
      do 1040 iw=iy,md
      vx=tens(iy,iw)
      tens(iy,iw)=tens(iz,iw)
      tens(iz,iw)=vx
 1040 continue
      vx=v(iy)
      v(iy)=v(iz)
      v(iz)=vx
      indic3=1
 1500 continue
      if(indic3.eq.1) go to 1005
 1600 continue
      inv=1
      do 1610 iy=1,md
      if(tens(iy,iy).eq.0.) inv=0
 1610 CONTINUE
      if(inv.eq.0) go to 2000
      do 2001 iy=md,2,-1
      do 1620 iw=iy-1,1,-1
      v(iw)=v(iw)-tens(iw,iy)*v(iy)/tens(iy,iy)
 1620 CONTINUE
 2001 CONTINUE
      do 1650 iy=1,md
      ih=iy
      x(ih)=v(ih)/tens(ih,ih)
 1650 continue
      return
 2000 end