/[MITgcm]/MITgcm/pkg/mnc/README.txt
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Revision 1.6 - (hide annotations) (download)
Fri Jan 16 03:32:42 2004 UTC (20 years, 4 months ago) by edhill
Branch: MAIN
Changes since 1.5: +14 -0 lines
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 o write all "grid-info" variables with or without the "halo"
 o templates for type conversion [ _RS | _RL ] ==> NetCDF real | double
 o add version info (from doc/tag-index) to NetCDF output to help
     track which version of MITgcm produced the output

1 edhill 1.1
2 edhill 1.2 API Discussions:
3     ================
4    
5 edhill 1.1 As discussed in our group meeting of 2003-12-17 (AJA, CNH, JMC, AM,
6     PH, EH3), the NetCDF interface should resemble the following FORTRAN
7     subroutines:
8    
9     1) "stubs" of the form: MNC_WV_[G|L]2D_R[S|L] ()
10    
11     2) MNC_INIT_VGRID( 'V_GRID_TYPE', nx, ny, nz, zc, zg )
12     1 1
13    
14     3) MNC_INIT_HGRID( 'H_GRID_TYPE', nx, ny, xc, yc, xg, yg )
15    
16     4) MNC_INIT_VAR( 'file', 'Vname', 'Vunits', 'H_GTYPE', 'V_GTYPE', PREC, FillVal )
17    
18     5) MNC_WRITE_VAR( 'file', 'Vname', var, bi, bj, myThid )
19    
20     This is a reasonable start but its inflexible since it isn't easily
21     generalized to grids with dimensions other than [2,3,4] or grids with
22     non-horizontal orientations (eg. vertical slices).
23    
24    
25     Generalizing what we would like to write as "variables defined on 1-D
26     to n-D grids", one can imagine a small number of objects containing
27     all the relevant information:
28    
29     a dimension: [ name, size, units ]
30     a grid: [ name, 1+ dim-ref ]
31     a variable: [ name, units, *1* grid-ref, data ]
32     an attribute: [ name, units, data ]
33     a NetCDF file: [ name, 0+ attr, 0+ grid-ref, 0+ var-ref ]
34    
35     which can then be manipulated (created, associated, destroyed, etc.)
36     using a simple interface such as:
37    
38     MNC_INIT( myThid )
39    
40 edhill 1.2 MNC_FILE_CREATE( myThid, fname )
41 edhill 1.1 MNC_FILE_OPEN( myThid, fname, itype )
42     MNC_FILE_ADD_ATTR_STR( myThid, fname, atname, sval )
43 edhill 1.5 MNC_FILE_ADD_ATTR_DBL( myThid, fname, atname, len, dval )
44     MNC_FILE_ADD_ATTR_REAL(myThid, fname, atname, len, rval )
45     MNC_FILE_ADD_ATTR_INT( myThid, fname, atname, len, ival )
46     MNC_FILE_ADD_ATTR_ANY( myThid, fname, atname, atype, cs,len,dv,rv,iv )
47 edhill 1.1 ...
48     MNC_FILE_READ_HEADER( myThid, fname )
49    
50     MNC_DIM_INIT( myThid, dname, dunits, dlen )
51 edhill 1.2 MNC_DIM_REMOVE( myThid, dname )
52 edhill 1.1
53     MNC_GRID_INIT( myThid, fname, gname, ndim, dnames )
54 edhill 1.2 MNC_GRID_SET_LL( myThid, fname, gname, type, lats, lons )
55 edhill 1.1
56 edhill 1.5 MNC_VAR_INIT_DBL( myThid, fname, gname, vname, units )
57     MNC_VAR_INIT_REAL( myThid, fname, gname, vname, units )
58     MNC_VAR_INIT_INT( myThid, fname, gname, vname, units )
59     MNC_VAR_INIT_ANY( myThid, fname, gname, vname, units, type )
60     MNC_VAR_ADD_ATTR_STR( myThid, fname, vname, atname, nv, sval )
61     MNC_VAR_ADD_ATTR_DBL( myThid, fname, vname, atname, nv, dval )
62     MNC_VAR_ADD_ATTR_REAL( myThid, fname, vname, atname, nv, rval )
63     MNC_VAR_ADD_ATTR_INT( myThid, fname, vname, atname, nv, ival )
64     MNC_VAR_ADD_ATTR_ANY( myThid, fname, vname, atname, atype, cs,len,dv,rv,iv )
65 edhill 1.4 MNC_VAR_WRITE_DBL( myThid, fname, vname, var )
66     MNC_VAR_WRITE_REAL( myThid, fname, vname, var )
67     MNC_VAR_WRITE_INT( myThid, fname, vname, var )
68 edhill 1.5 MNC_VAR_WRITE_ANY( myThid, fname, vname, vtype, dv, rv, iv )
69 edhill 1.1 ...
70 edhill 1.4 MNC_VAR_READ( myThid, fname, vname, var )
71 edhill 1.1
72     MNC_FILE_CLOSE( myThid, fname )
73    
74     The above interface is powerful yet easy to use (easier than the
75     entire NetCDF interface) since it helps the user keep track of the
76     associations between files, "grids", variables, and dimensions.
77 edhill 1.2
78    
79     To-Do:
80     ======
81    
82     1) CNH pointed out that grid interpolation needs to be handled
83     "on-the-fly" since pre-processing would result in overly large
84     input files. We need an interpolation API...
85 edhill 1.6
86     2) AM described her "diags" (or "myDiags" or "mDiags") interface
87     which should use MNC for output. The data storage idea is similar
88     to the MNC tables-of-indicies approach but also includes one huge
89     double-precision "accumulator" to hold all the temporary values
90     (eg. partial sums for averages, current max/mins):
91    
92     vname ( ni )
93     vlen ( ni )
94     vind ( ni ) -----+
95     |
96    
97     vij_diag ( i, j, [...] ) w/ lat/lon indicies
98     vgl_diag ( [...] ) wo/ lat/lon indicies (global)

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