mirror of https://github.com/ecmwf/eccodes.git
93 lines
3.0 KiB
Fortran
93 lines
3.0 KiB
Fortran
! Copyright 2005-2018 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 fields.
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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) :: size
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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
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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",size)
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allocate(values1(size), stat=iret)
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allocate(values2(size), 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,"setDecimalPrecision", &
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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,size
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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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endif
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if ( a .gt. maxa ) maxa=a
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if ( r .gt. maxr ) maxr=r
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enddo
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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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