program sum_r3dv_step

! **********************************************************************
! *              .      .    .
! * PROGRAM:    sum_r3dv_step
! * PRGMMR:     M. ZUPANSKI     ORG: CIRA/CSU   DATE: 2003-09-10
! *
! * ABSTRACT:   STEP-LENGTH RELATED COMPONENTS OF OBSERVATIONAL COST FUNCTION
! *             Calculate the inner products for step-length update
! *
! *    INPUT:   res_trial  = R**(-1/2)*(y-Hx) (trial obs residual)
! *             res        = R**(-1/2)*(y-Hx) (old-previous iteration obs residual)
! *
! * PROGRAM LOG:
! *
! * 09/10/2003    ..... M. ZUPANSKI:
! *
! **********************************************************************
      integer,parameter :: ires_trial=21    !! trial residual
      integer,parameter :: ires=22          !! old residual
      integer,parameter :: icost=51         !! obs cost function contributions

      real cost_top,cost_bot

      integer NUM_total
      integer NUM

      real,dimension(:),allocatable :: res,res_trial

!===========================================================

!--- initialize step-length sums (obs contributions)

          cost_top=0.0
          cost_bot=0.0

!----
!
!     READ THE OBS RESIDUALS
!
      CLOSE(ires_trial)
      OPEN(UNIT=ires_trial,FILE='res_trial',FORM='UNFORMATTED',IOSTAT=IER)
      READ(ires_trial) mdata
      allocate(res_trial(1:mdata))
      READ(ires_trial) res_trial
      CLOSE(ires_trial,status='KEEP')

      CLOSE(ires)
      OPEN(UNIT=ires,FILE='res_cntrl',FORM='UNFORMATTED',IOSTAT=IER)
      READ(ires) NUM
      allocate(res(1:NUM))
      READ(ires) res
      CLOSE(ires,status='KEEP')

      if(NUM.eq.mdata) then
      write(*,*) "ALL is fine, number of obs match"
      else
      write(*,*) "PROBLEM: Number of obs DOES NOT match: mdata=",mdata," NUM=",NUM
      stop
      end if

!
!   PROCESS COST-FUNCTION
!
          do i=1,NUM
          cost_top=cost_top+(res(i)-res_trial(i))*res(i)
          cost_bot=cost_bot+(res(i)-res_trial(i))*(res(i)-res_trial(i))
          end do


       write(3,*)"=============================================="
       write(3,*)"TOTAL NUMBER OF OBSERVATIONS "
       write(3,*)"=============================================="
       write(3,*)"NUM_total=  ",NUM
       write(3,*)"=============================================="


      WRITE(3,*)"=========OBSERVATIONAL STEP COST FUNCTION============"

      WRITE(3,8801) cost_top
      WRITE(3,8802) cost_bot

 8801 FORMAT('TRIAL COST-FUNCTION: SSTOP=',E15.7)
 8802 FORMAT('TRIAL COST-FUNCTION: SSBOT=',E15.7/)


!     WRITE OUT THE TOTAL COST-FUNCTION
!
      CLOSE(icost)
      OPEN(UNIT=icost,FILE='obssum',FORM='UNFORMATTED',IOSTAT=IER)
      WRITE(icost) cost_top,cost_bot
      CLOSE(icost,STATUS='KEEP')


stop
end