VMAT_lab2_24

program lab2
integer, parameter :: N = 6, alpha = 4
real, dimension(N, N) :: Q
real, dimension(N) :: Z, g, IPVT, WORK
real :: u = 2.0, x, y, COND, res

 do k=1, N
  g(k) = 2.0**(k-4.0)
 end do

do l=1,4
u = u / 10.0
x = 4 + u
y = 4 - u
do i=1,N
  do j=1, N
    if ( i > j) then
      Q(i,j) = y
      cycle
    end if
    if (i < j) then
      Q(i,j) = x
      cycle
    end if
    Q(i,j) = alpha

  end do
end do

do i=1,N

  Z(i) = y * sum(g(1:i-1)) + alpha * g(i) + x * sum(g(i+1:N))

end do

call DECOMP (N,N,Q,COND,IPVT,WORK)
call SOLVE (N,N,Q,Z,IPVT)
write(*,*) "COND = ", COND
write(*,*) "u = ", u
write(*,*) "g = ", g
write(*,*) "z = ", z

res = sum(abs(z-g)) / sum(abs(g))
write(*,*) "RESULT = ", res
write(*,*) "---------------------------------"
end do

end program lab2