[数值问题] do循环，数组越界1位（value 4 超过bound 3）

program main
    implicit none
    real::a(3,3)=(/10,-1,-1,-1,10,-1,-2,-2,5/)
    real::b(3)=(/7.2,8.3,4.2/)
    real x(3)
    real i,j,time,k,ii,o(3),keep(3),ans,ans1,ans2
    call Jacobi(i,j,time,ans,o,keep,x,a,b)
    call Gauss_Seidel(i,j,time,k,ii,o,keep,ans1,ans2,a,b,x)
    pause
    end program main
    
    subroutine Jacobi(i,j,time,ans,o,keep,x,a,b)
    implicit none
    real ans,o(3),keep(3),x(3),a(3,3),b(3),i,j,time
    x(1)=0
    x(2)=0
    x(3)=0
    do time=1,10
        do i=1,3
        keep(i)=x(i)
        ans=0
           do j=1,3
              if(j==i) cycle
              ans=ans+a(i,j)*x(j)
           end do
        x(i)=(b(i)-ans)/a(i,i)
        o(i)=abs(x(i)-keep(i))
        end do
        write(*,*) x(1),x(2),x(3)
    if(o(1)<0.001 .and.o(2)<0.001 .and.o(3)<0.001 ) exit
    write(*,*) 'This is the answer!'
    end do
    return
    pause
    end
    
    subroutine Gauss_Seidel(i,j,time,k,ii,o,keep,ans1,ans2,a,b,x)
    implicit none
    real o(3),keep(3),a(3,3),b(3),x(3)
    real ans1,ans2,i,j,time,k,ii
    x(1:3)=0
    do time=1,10
        do i=1,3
        keep(i)=x(i)
        end do
        ans1=0
        ans2=0
           do j=2,3
           ans1=ans1+a(1,j)*x(j)
           end do
           x(1)=(b(1)-ans1)/a(1,1)
           x(2)=(b(2)-a(2,1)*x(1)-a(2,3)*x(3))/a(2,2)
           do k=1,2
           ans2=ans2+a(3,k)*x(k)
           end do
           x(3)=(b(3)-ans2)/a(3,3)
        do ii=1,3
        o(ii)=abs(x(ii)-keep(ii))
        end do
        write(*,*) x(1),x(2),x(3)
    if(o(1)<0.001 .and.o(2)<0.001 .and.o(3)<0.001) exit
    write(*,*) 'This is the answer!'
    end do
    return
    pause
    end