mirror of https://github.com/ecmwf/eccodes.git
93 lines
3.1 KiB
Fortran
93 lines
3.1 KiB
Fortran
! (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))
|
|
end if
|
|
if (a .gt. maxa) maxa = a
|
|
if (r .gt. maxr) maxr = r
|
|
end do
|
|
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
|