1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
|
C (C) Copyright 2005- ECMWF.
C
C This software is licensed under the terms of the Apache Licence Version 2.0
C which can be obtained at http://www.apache.org/licenses/LICENSE-2.0.
C
C In applying this licence, ECMWF does not waive the privileges and immunities granted to it by
C virtue of its status as an intergovernmental organisation nor does it submit to any jurisdiction.
C
C
C
C Fortran 77 Implementation: precision
C
C Description: how to control decimal precision when packing fields.
C
C
C
C
C
program precision
implicit none
integer maxNumberOfValues
parameter (maxNumberOfValues=10000)
include 'grib_api_fortran.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,"setDecimalPrecision"
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
|
