mirror of https://github.com/ecmwf/eccodes.git
94 lines
3.1 KiB
Fortran
94 lines
3.1 KiB
Fortran
! (C) Copyright 2005- ECMWF.
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!
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! This software is licensed under the terms of the Apache Licence Version 2.0
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! which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
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!
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! In applying this licence, ECMWF does not waive the privileges and immunities granted to it by
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! virtue of its status as an intergovernmental organisation nor does it submit to any jurisdiction.
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!
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!
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! Description: How to control decimal precision when packing GRIB fields.
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!
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!
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!
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program precision
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use eccodes
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implicit none
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integer(kind=4) :: size1
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integer :: infile, outfile
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integer :: igrib
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real(kind=8), dimension(:), allocatable :: values1
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real(kind=8), dimension(:), allocatable :: values2
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real(kind=8) :: maxa, a, maxv, minv, maxr, r=0
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integer(kind=4) :: decimalPrecision, bitsPerValue1, bitsPerValue2
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integer :: i, iret
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call codes_open_file(infile, &
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'../../data/regular_latlon_surface_constant.grib1', 'r')
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call codes_open_file(outfile, &
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'../../data/regular_latlon_surface_prec.grib1', 'w')
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! a new grib message is loaded from file
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! igrib is the grib id to be used in subsequent calls
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call codes_grib_new_from_file(infile, igrib)
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! bitsPerValue before changing the packing parameters
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call codes_get(igrib, 'bitsPerValue', bitsPerValue1)
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! get the size of the values array
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call codes_get_size(igrib, "values", size1)
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allocate (values1(size1), stat=iret)
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allocate (values2(size1), stat=iret)
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! get data values before changing the packing parameters*/
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call codes_get(igrib, "values", values1)
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! setting decimal precision=2 means that 2 decimal digits
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! are preserved when packing.
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decimalPrecision = 2
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call codes_set(igrib, "changeDecimalPrecision", decimalPrecision)
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! bitsPerValue after changing the packing parameters
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call codes_get(igrib, "bitsPerValue", bitsPerValue2)
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! get data values after changing the packing parameters
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call codes_get(igrib, "values", values2)
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! computing error
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maxa = 0
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maxr = 0
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maxv = values2(1)
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minv = maxv
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do i = 1, size1
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a = abs(values2(i) - values1(i))
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if (values2(i) .gt. maxv) maxv = values2(i)
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if (values2(i) .lt. maxv) minv = values2(i)
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if (values2(i) .ne. 0) then
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r = abs((values2(i) - values1(i))/values2(i))
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end if
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if (a .gt. maxa) maxa = a
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if (r .gt. maxr) maxr = r
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end do
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write (*, *) "max absolute error = ", maxa
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write (*, *) "max relative error = ", maxr
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write (*, *) "min value = ", minv
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write (*, *) "max value = ", maxv
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write (*, *) "old number of bits per value=", bitsPerValue1
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write (*, *) "new number of bits per value=", bitsPerValue2
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! write modified message to a file
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call codes_write(igrib, outfile)
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call codes_release(igrib)
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call codes_close_file(infile)
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call codes_close_file(outfile)
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deallocate (values1)
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deallocate (values2)
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end program precision
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