C IMP03D    SOURCE    PV090527  23/01/27    21:15:41     11574          
        subroutine imp03d(numz,aa,bb,ngf,valz)
        
c      modification du systeme lineaire pour imposer une valeur        

       implicit real*8 (a-h,o-z)
       implicit integer (i-n)
       
       integer ngf,numz
       real*8 aa(ngf,ngf+1),bb(ngf)
       real*8 valz
       do idir=1,ndim_solve
            aa(numz,idir)=0.d0
            aa(idir,numz)=0.d0
       end do
       bb(numz)=valz
       aa(numz,numz)=1.d0
       return
       end