
c---------------------------------------------------------------------
c---------------------------------------------------------------------

       subroutine  txinvr

c---------------------------------------------------------------------
c---------------------------------------------------------------------

c---------------------------------------------------------------------
c block-diagonal matrix-vector multiplication                  
c---------------------------------------------------------------------

       include 'header.h'

       integer c, i, j, k
       double precision t1, t2, t3, ac, ru1, uu, vv, ww, r1, r2, r3, 
     >                  r4, r5, ac2inv

c---------------------------------------------------------------------
c      loop over all cells owned by this node          
c---------------------------------------------------------------------
       do   c = 1, ncells
          do    k = start(3,c), cell_size(3,c)-end(3,c)-1
             do    j = start(2,c), cell_size(2,c)-end(2,c)-1
                do    i = start(1,c), cell_size(1,c)-end(1,c)-1

                   ru1 = rho_i(i,j,k,c)
                   uu = us(i,j,k,c)
                   vv = vs(i,j,k,c)
                   ww = ws(i,j,k,c)
                   ac = speed(i,j,k,c)
                   ac2inv = ainv(i,j,k,c)*ainv(i,j,k,c)

                   r1 = rhs(i,j,k,1,c)
                   r2 = rhs(i,j,k,2,c)
                   r3 = rhs(i,j,k,3,c)
                   r4 = rhs(i,j,k,4,c)
                   r5 = rhs(i,j,k,5,c)

                   t1 = c2 * ac2inv * ( qs(i,j,k,c)*r1 - uu*r2  - 
     >                  vv*r3 - ww*r4 + r5 )
                   t2 = bt * ru1 * ( uu * r1 - r2 )
                   t3 = ( bt * ru1 * ac ) * t1

                   rhs(i,j,k,1,c) = r1 - t1
                   rhs(i,j,k,2,c) = - ru1 * ( ww*r1 - r4 )
                   rhs(i,j,k,3,c) =   ru1 * ( vv*r1 - r3 )
                   rhs(i,j,k,4,c) = - t2 + t3
                   rhs(i,j,k,5,c) =   t2 + t3
                end do
             end do
          end do
       end do

       return
       end