C Copyright 2005-2007 ECMWF C C Licensed under the GNU Lesser General Public License which C incorporates the terms and conditions of version 3 of the GNU C General Public License. C See LICENSE and gpl-3.0.txt for details. C C C Fortran 77 Implementation: precision C C Description: how to control decimal precision when packing fields. C C C Author: Enrico Fucile <enrico.fucile@ecmwf.int> C C C program precision implicit none integer maxNumberOfValues parameter (maxNumberOfValues=10000) include 'grib_api_f77.h' integer*4 size integer infile,outfile integer igrib real*8 values1(maxNumberOfValues) real*8 values2(maxNumberOfValues) real*8 maxa,a,maxv,minv,maxr,r integer*4 decimalPrecision,bitsPerValue1,bitsPerValue2 integer i call grib_check(grib_open_file(infile X,'../../data/regular_latlon_surface.grib1','r')) call grib_check(grib_open_file(outfile X,'../../data/regular_latlon_surface_prec.grib1','w')) C a new grib message is loaded from file C igrib is the grib id to be used in subsequent calls call grib_check(grib_new_from_file(infile,igrib)) C bitsPerValue before changing the packing parameters call grib_check(grib_get_int(igrib,'bitsPerValue',bitsPerValue1)) C get the size of the values array call grib_check(grib_get_size(igrib,"values",size)) C get data values before changing the packing parameters*/ call grib_check(grib_get_real8_array(igrib,"values",values1,size)) C setting decimal precision=2 means that 2 decimal digits C are preserved when packing. decimalPrecision=2 call grib_check(grib_set_int(igrib,"changeDecimalPrecision" X,decimalPrecision)) C bitsPerValue after changing the packing parameters call grib_check(grib_get_int(igrib,"bitsPerValue",bitsPerValue2)) C get data values after changing the packing parameters call grib_check(grib_get_real8_array(igrib,"values",values2,size)) C 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 C write modified message to a file call grib_check(grib_write(igrib,outfile)) call grib_check(grib_release(igrib)) call grib_check(grib_close_file(infile)) call grib_check(grib_close_file(outfile)) end