[子程序] 求助大佬，动态数组如何作子程序形参

program main
    use mod_assembly
    use mod_solver
    implicit none
    integer n
    real(kind=8),allocatable::a(:,:),b(:)
    real(kind=8),allocatable::x(:)
    real(kind=8) m,s
    n=4000
    allocate(a(n,n),b(n),x(n))
    call assembly(n,a,b)
    call lu_crout(a,b,x,n)
    end program main

subroutine assembly(a)
  real(8),allocatable::a(:,:)
end subroutine assembly

call assembly(a)

program main
    use mod_assembly
    use mod_solver
    implicit none
    integer n
    real(kind=8),allocatable::a(:,:),b(:)
    real(kind=8),allocatable::x(:)
    n=40000
    allocate(a(n,n),b(n),x(n))
    call assembly(n,a,b)
    call lu_crout(a,b,x,n)
    end program main

module mod_assembly
    contains
    
    subroutine assembly(n,a,b)
    implicit none
    integer n
    real(kind=8) a(n,n),b(n)
    integer i,j
    a=0.0_8
    do i=1,n
        do j=1,n
            if (i.eq.j) then
                a(i,j)=3.0_8
            elseif (abs(i-j).eq.2) then
                a(i,j)=1.0_8
            elseif (abs(i-j).eq.1) then
                a(i,j)=2.0_8
            endif
        enddo
    enddo
    b=1.0_8
    return
    end subroutine assembly
    end module mod_assembly

module mod_solver
    contains
    subroutine lu_crout(A,b,xx,N)
    implicit none
    integer N
    real(kind=8) A(n,n),b(n),xx(n)
    real(kind=8) L(N,N),U(N,N)
    real(kind=8) y(N)
    call crout(A,L,U,N)
    call downtri(L,b,y,N)
    call uptri(U,y,xx,N)
    end subroutine lu_crout
    
    subroutine crout(A,L,U,N)
    implicit none
    integer N,i,k,r,j
    real(kind=8) s
    real(kind=8) A(n,n)
    real(kind=8) L(N,N),U(N,N)
    l=0.0_8
    u=0.0_8
    L(:,1)=a(:,1)
    U(1,:)=a(1,:)/L(1,1)
    do k=2,N
        do i=k,n
            s=0
            do r=1,k-1
                s=s+l(i,r)*u(r,k)
            end do
            l(i,k)=a(i,k)-s
        end do
        do j=k+1,n
            s=0
            do r=1,k-1
                s=s+l(k,r)*u(r,j)
            end do
            u(k,j)=(a(k,j)-s)/l(k,k)
        end do
        u(k,k)=1
    end do
    return
    end subroutine crout
    
    subroutine uptri(A,b,xx,N)
implicit none
integer::i,j,N
real(kind=8) A(n,n),b(N),xx(N)
xx(N)=b(N)/A(N,N)
do i=n-1,1,-1
    xx(i)=b(i)
   do j=i+1,N
    xx(i)=xx(i)-a(i,j)*xx(j)
   end do
    xx(i)=xx(i)/A(i,i)
end do
return
    end subroutine uptri
    
    subroutine downtri(A,b,xx,N)
    implicit none
    integer N,k,i
    real(kind=8) A(n,n),b(N),xx(N)
    xx(1)=b(1)/a(1,1)
    do k=2,N
        xx(k)=b(k)
        do i=1,k-1
            xx(k)=xx(k)-a(k,i)*xx(i)
        end do
        xx(k)=xx(k)/a(k,k)
    end do
    end subroutine downtri
    end module mod_solver