!###########################################################
! page.108-110 表5.3(例題6)
! SOR法のプログラム
!###########################################################
PROGRAM prog21
IMPLICIT REAL(8)(a-h,o-z)
IMPLICIT INTEGER(i-n)

INTEGER,PARAMETER :: KMAX=100,N=2
REAL(8),DIMENSION(N) :: xx1,xx2

!---------------
xx1=0.d0
xx2=0.d0

omega=1.2d0
delta=1.d-8
!---------------

k=0
WRITE(*,"('k=',i2,' x=',1P5E14.6)") k,xx1

DO k=1,KMAX

xx2(1)=omega*(13.d0-4.d0*xx1(2))/5.d0 +(1.d0-omega)*xx1(1)
xx2(2)=omega*( 8.d0-2.d0*xx2(1))/3.d0 +(1.d0-omega)*xx1(2)

WRITE(*,"('k=',i2,' x=',1P5E14.6)") k,xx2
fsum=SUM((xx2-xx1)**2)
IF(fsum<delta)GOTO 100

xx1=xx2
xx2=0.d0

END DO
WRITE(*,*) '解が求まりませんでした'
STOP

100 CONTINUE
WRITE(*,*)
WRITE(*,*) "SOR法で求めた解は"
WRITE(*,"('x=',1P5E14.6)") xx2

STOP
END PROGRAM prog21
!###########################################################