subroutine  linear_solver(A, b, x, n, info)

c-------------------------------------------------
c
c  Driver to solve the linear system:
c      A * x = b
c  using the LAPACK routine DGESV
c  (A being a general matrix)  
c
c  UBC,  Sep 2 2000
c
c-------------------------------------------------

         implicit    none

         character*13  cdnm
         parameter   ( cdnm = 'linear_solver' ) 

         logical       ltrace
         parameter   ( ltrace = .false. )

         integer       n

         real*8        A(n,n),    AT(n,n)
         real*8        b(n),    x(n) 

         integer       nrhs

c------------------------------------------------
c   Leading order of the vectors.  (???)
c------------------------------------------------

         integer       lda,     ldb

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

         integer       ipiv(n)
         integer       info   

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

         integer       i,     j

c================================================
c================================================
         if  ( ltrace ) then
             write(0,*) cdnm,': A=',A
             write(0,*) cdnm,': b=',b
             write(0,*) cdnm,': n=',n
         endif
         if ( n .le. 0 ) then
            write(0,*) cdnm,': Dimension of the system 0 !!'
            return
         endif  
         nrhs = 1
         lda  = n
         ldb  = n
         do i =1 , n  
            do j = 1, n
               AT(j,i) = A(i,j)
            enddo
         enddo
         call dgesv(n, nrhs, AT, lda, ipiv, b, ldb, info) 
         do i = 1 , n
            x(i) = b(i)
         enddo 
         if ( ltrace ) then
            if ( info .eq. 0 ) write(0,*) cdnm,': System solved '//
     &                                    'successfully.'
            write(0,*) cdnm,': x=',x 
            write(0,*) cdnm,': ipiv=',ipiv 
         endif
         if ( info .lt. 0 ) then
            write(0,*) '#######################################'
            write(0,*) cdnm,': Cant solve the linear system !!!'
            write(0,*) cdnm,': info =',info
            write(0,*) cdnm,': Check the ',info,'-th argument to DGESV'          
            write(0,*) '#######################################'
         endif
         if ( info .gt. 0 ) then

            write(0,*) '#######################################'
            write(0,*) cdnm,': Cant solve the linear system !!!'
            write(0,*) cdnm,': info =',info
            write(0,*) cdnm,': U(',info,',',info,')=0 !!!'          
            write(0,*) '#######################################'
         endif
         return
         end