c
c Numerical Analysis:
c The Mathematics of Scientific Computing
c D.R. Kincaid & E.W. Cheney
c Brooks/Cole Publ., 1990
c
c Section 2.3
c
c Example of unstable sequence
c
c
c file: unstab2.f
c
dimension x(0:15),y(0:15),e(0:15),f(0:15)
double precision y
c
print *
print *,' Unstable sequence'
print *,' Section 2.3, Kincaid-Cheney'
print *
print 4,'n','x(n)','true','error','rel. error'
c
x(0) = 1.0
x(1) = 4.0
y(0) = 1.d0
y(1) = 4.d0
c
do 2 n=1,14
x(n+1) = (13./3.)*x(n) - (4./3.)*x(n-1)
y(n+1) = (4.d0)**(n+1)
2 continue
c
do 3 n=0,15
e(n) = real(dble(x(n)) - y(n))
f(n) = abs(e(n)/real(y(n)))
print 5,n,x(n),real(y(n)),e(n),f(n)
3 continue
c
4 format (a6,a10,a15,a16,a19)
5 format(1x,i5,4(2x,e13.6))
stop
end
.