c-----------------------------------------------------------------------
c        
c\Example-1
c     ... Suppose want to solve A*x = lambda*x in regular mode
c     ... so OP = A  and  B = I.
c     ... Assume "call matvecA(n,x,y)" computes y = A*x
c     ... Assume exact shifts are used
c     ...
c     ido = 0
c     iparam(7) = 1
c
c     %------------------------------------%
c     | Beginning of reverse communication |
c     %------------------------------------%
c 10  continue
c     call _saupd ( ido, 'I', n, which, nev, tol, resid, ncv, v, ldv, iparam,
c    &              ipntr, workd, workl, lworkl, info )
c     if (ido .eq. -1 .or. ido .eq. 1) then
c        call matvecA (n, workd(ipntr(1)), workd(ipntr(2)))
c        go to 10
c     end if 
c     %------------------------------%
c     | End of Reverse communication |
c     %------------------------------%
c
c     ... Call _seupd to postprocess
c     ... want the Ritz vectors set rvec = .true. else rvec = .false.
c     call _seupd ( rvec, 'All', select, d, z, ldz, sigma, bmat,
c    &              n, which, nev, tol, resid, ncv, v, ldv, iparam, 
c    &              ipntr, workd, workl, lworkl, info )
c
c     stop
c     end
c
c\Example-2
c     ... Suppose want to solve A*x = lambda*x in shift-invert mode
c     ... so OP = inv[A - sigma*I]  and  B = I.
c     ... Assume "call solve(n,rhs,x)" solves [A - sigma*I]*x = rhs
c     ... Assume exact shifts are used
c     ...
c     ido = 0
c     iparam(7) = 3
c
c     %------------------------------------%
c     | Beginning of reverse communication |
c     %------------------------------------%
c 10  continue
c     call _saupd ( ido, 'I', n, which, nev, tol, resid, ncv, v, ldv, iparam,
c    &              ipntr, workd, workl, lworkl, info )
c     if (ido .eq. -1 .or. ido .eq. 1) then
c        call solve (n, workd(ipntr(1)), workd(ipntr(2)))
c        go to 10
c     end if
c     %------------------------------%
c     | End of Reverse communication |
c     %------------------------------%
c
c     ... Call _seupd to postprocess
c     ... want the Ritz vectors set rvec = .true. else rvec = .false.
c     call _seupd ( rvec, 'All', select, d, z, ldz, sigma, bmat,
c    &              n, which, nev, tol, resid, ncv, v, ldv, iparam, 
c    &              ipntr, workd, workl, lworkl, info )
c
c\Example-3
c     ... Suppose want to solve A*x = lambda*M*x in regular mode
c     ... so OP = inv[M]*A  and  B = M.
c     ... Assume "call matvecM(n,x,y)"  computes y = M*x
c     ... Assume "call matvecA(n,x,y)"  computes y = A*x
c     ... Assume "call solveM(n,rhs,x)" solves   M*x = rhs
c     ... Assume user will supplied shifts
c     ...
c     ido = 0
c     iparam(7) = 2
c
c     %------------------------------------%
c     | Beginning of reverse communication |
c     %------------------------------------%
c 10  continue
c     call _saupd ( ido, 'G', n, which, nev, tol, resid, ncv, v, ldv, iparam,
c    &              ipntr, workd, workl, lworkl, info )
c     if (ido .eq. -1 .or. ido .eq. 1) then
c        call matvecA (n, workd(ipntr(1)), temp_array)
c        call _scopy (n, temp_array, 1, workd(ipntr(1)), 1)
c        call solveM  (n, temp_array, workd(ipntr(2)))
c        go to 10
c     else if (ido .eq. 2) then
c        call matvecM (n, workd(ipntr(1)), workd(ipntr(2)))
c        go to 10
c
c     ... delete this last conditional if want to use exact shifts
c     else if (ido .eq. 3) then
c        ... compute shifts and put in the first np locations of work
c        np = iparam(8)
c        call _copy (np, shifts, 1, workl(ipntr(11), 1)
c        go to 10
c     end if
c     %------------------------------%
c     | End of Reverse communication |
c     %------------------------------%
c
c     ... call _seupd to postprocess 
c     ... want the Ritz vectors set rvec = .true. else rvec = .false.
c     call _seupd ( rvec, 'All', select, d, z, ldz, sigma, bmat,
c    &              n, which, nev, tol, resid, ncv, v, ldv, iparam, 
c    &              ipntr, workd, workl, lworkl, info )
c     stop
c     end
c
c\Example-4
c     ... Suppose want to solve A*x = lambda*M*x in shift-invert mode
c     ... so OP = (inv[A - sigma*M])*M  and  B = M.
c     ... Assume "call matvecM(n,x,y)" computes y = M*x
c     ... Assume "call solve(n,rhs,x)" solves [A - sigma*M]*x = rhs
c     ... Assume exact shifts are used
c     ...
c     ido = 0
c     iparam(7) = 3
c
c     %------------------------------------%
c     | Beginning of reverse communication |
c     %------------------------------------%
c 10  continue
c     call _saupd ( ido, 'G', n, which, nev, tol, resid, ncv, v, ldv, iparam,
c    &              ipntr, workd, workl, lworkl, info )
c     if (ido .eq. -1) then
c        call matvecM (n, workd(ipntr(1)), temp_array)
c        call solve (n, temp_array, workd(ipntr(2)))
c        go to 10
c     else if (ido .eq. 1) then
c        call solve (n, workd(ipntr(3)), workd(ipntr(2)))
c        go to 10  
c     else if (ido .eq. 2) then
c        call matvecM (n, workd(ipntr(1)), workd(ipntr(2)))
c        go to 10
c     end if
c     %------------------------------%
c     | End of Reverse communication |
c     %------------------------------%
c
c     ... call _seupd to postprocess
c     ... want the Ritz vectors set rvec = .true. else rvec = .false.
c     call _seupd ( rvec, 'All', select, d, z, ldz, sigma, bmat,
c    &              n, which, nev, tol, resid, ncv, v, ldv, iparam, 
c    &              ipntr, workd, workl, lworkl, info )
c
c     stop
c     end 
c        
c\Example-5
c     ... Suppose want to solve K*x = lambda*KG*x in Buckling mode
c     ... so OP = (inv[K - sigma*KG])*K  and  B = K.
c     ... Assume "call matvecM(n,x,y)" computes y = KG*x
c     ... Assume "call matvecA(n,x,y)" computes y = K*x
c     ... Assume "call solve(n,rhs,x)" solves [K - sigma*KG]*x = rhs
c     ... Assume exact shifts are used
c
c     ido = 0
c     iparam(7) = 4
c
c     %------------------------------------%
c     | Beginning of reverse communication |
c     %------------------------------------%
c 10  continue
c     call _saupd ( ido, 'G', n, which, nev, tol, resid, ncv, v, ldv, iparam, 
c    &              ipntr, workd, workl, lworkl, info )
c     if (ido .eq. -1) then
c        call matvecA (n, workd(ipntr(1)), temp_array)
c        solve (n, temp_array, workd(ipntr(2)))
c        go to 10
c     else if (ido .eq. 1) then
c        call solve (n, workd(ipntr(3)), workd(ipntr(2)))
c        go to 10
c     else if (ido .eq. 2) then
c        call matvecA (n, workd(ipntr(1)), workd(ipntr(2)))
c        go to 10
c     end if
c     %------------------------------%
c     | End of Reverse communication |
c     %------------------------------%
c
c     ... call _seupd to postprocess 
c     ... want the Ritz vectors set rvec = .true. else rvec = .false.
c     call _seupd ( rvec, 'All', select, d, z, ldz, sigma, bmat,
c    &              n, which, nev, tol, resid, ncv, v, ldv, iparam,
c    &              ipntr, workd, workl, lworkl, info )
c     stop
c     end
c
c\Example-6
c     ... Suppose want to solve A*x = lambda*M*x in Cayley mode
c     ... so OP = inv[A - sigma*M]*[A + sigma*M]  and  B = M.
c     ... Assume "call matvecM(n,x,y)" computes y = M*x
c     ... Assume "call matvecA(n,x,y)" computes y = A*x
c     ... Assume "call solve(n,rhs,x)" solves [A - sigma*M]*x = rhs
c     ... Assume exact shifts are used
c     ...
c     ido = 0
c     iparam(7) = 5
c
c     %------------------------------------%
c     | Beginning of reverse communication |
c     %------------------------------------%
c 10  continue
c     call _saupd ( ido, 'G', n, which, nev, tol, resid, ncv, v, ldv, iparam,
c    &              ipntr, workd, workl, lworkl, info )
c     if (ido .eq. -1) then
c        call matvecM (n, workd(ipntr(1)), workd(ipntr(2)))
c        call matvecA (n, workd(ipntr(1)), temp_array)
c        call _axpy (n, sigma, workd(inptr(2)), 1, temp_array, 1)
c        call solve (n, temp_array, workd(ipntr(2)))
c        go to 10
c     else if (ido .eq. 1) then
c        call matvecA (n, workd(ipntr(1)), workd(ipntr(2)))
c        call _axpy (n, sigma, workd(inptr(3)), 1, workd(ipntr(2)), 1)
c        call _copy (n, workd(inptr(2)), 1, workd(ipntr(3)), 1)
c        call solve (n, workd(ipntr(3)), workd(ipntr(2)))
c        go to 10
c     else if (ido .eq. 2) then
c        call matvecM (n, workd(ipntr(1)), workd(ipntr(2)))
c        go to 10
c     end if
c     %------------------------------%
c     | End of Reverse communication |
c     %------------------------------%
c
c     ... call _seupd to postprocess
c     ... want the Ritz vectors set rvec = .true. else rvec = .false.
c     call _seupd ( rvec, 'All', select, d, z, ldz, sigma, bmat,
c    &              n, which, nev, tol, resid, ncv, v, ldv, iparam, 
c    &              ipntr, workd, workl, lworkl, info )
c     stop
c     end 
c\EndDoc
c