mirror of https://github.com/ecmwf/eccodes.git
98 lines
3.0 KiB
Fortran
98 lines
3.0 KiB
Fortran
C Copyright 2005-2014 ECMWF.
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C
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C This software is licensed under the terms of the Apache Licence Version 2.0
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C which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
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C
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C In applying this licence, ECMWF does not waive the privileges and immunities granted to it by
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C virtue of its status as an intergovernmental organisation nor does it submit to any jurisdiction.
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C
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C
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C
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C Fortran 77 Implementation: precision
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C
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C Description: how to control decimal precision when packing fields.
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C
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C
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C
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C
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C
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program precision
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implicit none
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integer maxNumberOfValues
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parameter (maxNumberOfValues=10000)
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include 'grib_api_fortran.h'
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integer*4 size
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integer infile,outfile
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integer igrib
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real*8 values1(maxNumberOfValues)
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real*8 values2(maxNumberOfValues)
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real*8 maxa,a,maxv,minv,maxr,r
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integer*4 decimalPrecision,bitsPerValue1,bitsPerValue2
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integer i
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call grib_check(grib_open_file(infile
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X,'../data/regular_latlon_surface.grib1','r'))
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call grib_check(grib_open_file(outfile
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X,'../data/regular_latlon_surface_prec.grib1','w'))
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C a new grib message is loaded from file
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C igrib is the grib id to be used in subsequent calls
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call grib_check(grib_new_from_file(infile,igrib))
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C bitsPerValue before changing the packing parameters
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call grib_check(grib_get_int(igrib,'bitsPerValue',bitsPerValue1))
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C get the size of the values array
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call grib_check(grib_get_size(igrib,"values",size))
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C get data values before changing the packing parameters*/
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call grib_check(grib_get_real8_array(igrib,"values",values1,size))
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C setting decimal precision=2 means that 2 decimal digits
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C are preserved when packing.
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decimalPrecision=2
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call grib_check(grib_set_int(igrib,"setDecimalPrecision"
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X,decimalPrecision))
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C bitsPerValue after changing the packing parameters
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call grib_check(grib_get_int(igrib,"bitsPerValue",bitsPerValue2))
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C get data values after changing the packing parameters
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call grib_check(grib_get_real8_array(igrib,"values",values2,size))
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C 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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C write modified message to a file
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call grib_check(grib_write(igrib,outfile))
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call grib_check(grib_release(igrib))
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call grib_check(grib_close_file(infile))
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call grib_check(grib_close_file(outfile))
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end
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