program inner_product
!**********************************************************************
! *              .      .    .
! * PROGRAM:    INNER_PRODUCT
! * PRGMMR:     M. ZUPANSKI     ORG: CIRA/CSU   DATE: 2003-10-21
! *
! * ABSTRACT:   CALCULATE INNER PRODUCT BETWEEN TWO VECTORS
! *
! * PROGRAM LOG:
! *
! * 10/21/2003    ..... M. ZUPANSKI:
! *
! **********************************************************************
!----------------------------------
!  INPUT: 
!         x_1 - 1st vector
!         x_2 - 2nd vector
!
!  OUTPUT:
!         product - inner product: (x_1**T)*x_2
!
!----------------------------------
!-----
     integer,parameter::ifile1=20         ! input file #
     integer,parameter::inner=51          ! output file #
!-----
     integer :: N_dim,NN

     real :: product
     real,dimension(:),allocatable::x_1
!-----
!==============start calculation===================

!-- read 1st file
     rewind ifile1
     read(ifile1) N_dim
     allocate(x_1(1:N_dim))
     read(ifile1) x_1

     write(*,*) "N_obs=",N_dim
!-- Inner product --------------------

       product=0.0
        do i=1,N_dim
       product=product+x_1(i)*x_1(i)
        end do

       write(*,*) "Raw product=",product

       product=product/float(N_dim)
       write(*,*) "Normalized product=",product

!!     product=sqrt(product)
!!     write(*,*) "Normalized sqrt product=",product

      rewind inner
      write(inner,100) product
 100  format(E20.10)

            stop
            end