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! (C) Copyright 2005- ECMWF.
!
! This software is licensed under the terms of the Apache Licence Version 2.0
! which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
!
! In applying this licence, ECMWF does not waive the privileges and immunities granted to it by
! virtue of its status as an intergovernmental organisation nor does it submit to any jurisdiction.
!
!
! Description: how to control decimal precision when packing fields.
!
!
program precision
use eccodes
implicit none
integer(kind = 4) :: size
integer :: infile,outfile
integer :: igrib
real(kind = 8), dimension(:), allocatable :: values1
real(kind = 8), dimension(:), allocatable :: values2
real(kind = 8) :: maxa,a,maxv,minv,maxr,r
integer( kind = 4) :: decimalPrecision,bitsPerValue1,bitsPerValue2
integer :: i, iret
call codes_open_file(infile, &
'../../data/regular_latlon_surface_constant.grib1','r')
call codes_open_file(outfile, &
'../../data/regular_latlon_surface_prec.grib1','w')
! a new grib message is loaded from file
! igrib is the grib id to be used in subsequent calls
call codes_grib_new_from_file(infile,igrib)
! bitsPerValue before changing the packing parameters
call codes_get(igrib,'bitsPerValue',bitsPerValue1)
! get the size of the values array
call codes_get_size(igrib,"values",size)
allocate(values1(size), stat=iret)
allocate(values2(size), stat=iret)
! get data values before changing the packing parameters*/
call codes_get(igrib,"values",values1)
! setting decimal precision=2 means that 2 decimal digits
! are preserved when packing.
decimalPrecision=2
call codes_set(igrib,"setDecimalPrecision", &
decimalPrecision)
! bitsPerValue after changing the packing parameters
call codes_get(igrib,"bitsPerValue",bitsPerValue2)
! get data values after changing the packing parameters
call codes_get(igrib,"values",values2)
! computing error
maxa=0
maxr=0
maxv=values2(1)
minv=maxv
do i=1,size
a=abs(values2(i)-values1(i))
if ( values2(i) .gt. maxv ) maxv=values2(i)
if ( values2(i) .lt. maxv ) minv=values2(i)
if ( values2(i) .ne. 0 ) then
r=abs((values2(i)-values1(i))/values2(i))
endif
if ( a .gt. maxa ) maxa=a
if ( r .gt. maxr ) maxr=r
enddo
write(*,*) "max absolute error = ",maxa
write(*,*) "max relative error = ",maxr
write(*,*) "min value = ",minv
write(*,*) "max value = ",maxv
write(*,*) "old number of bits per value=",bitsPerValue1
write(*,*) "new number of bits per value=",bitsPerValue2
! write modified message to a file
call codes_write(igrib,outfile)
call codes_release(igrib)
call codes_close_file(infile)
call codes_close_file(outfile)
deallocate(values1)
deallocate(values2)
end program precision
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