/[MITgcm]/MITgcm/pkg/mnc/README.txt
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Revision 1.10 - (hide annotations) (download)
Sat Jan 31 04:13:09 2004 UTC (20 years, 4 months ago) by edhill
Branch: MAIN
CVS Tags: hrcube4, checkpoint52j_post, checkpoint52k_post, checkpoint52j_pre, hrcube_3
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 o more work on the file-independent layer ("wrapper")

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 edhill 1.8 2) MNC_INIT_VGRID('V_GRID_TYPE', nx, ny, nz, zc, zg)
12 edhill 1.1
13 edhill 1.8 3) MNC_INIT_HGRID('H_GRID_TYPE', nx, ny, xc, yc, xg, yg)
14 edhill 1.1
15 edhill 1.8 4) MNC_INIT_VAR('file', 'Vname', 'Vunits', 'H_GTYPE', 'V_GTYPE', PREC, FillVal)
16 edhill 1.1
17 edhill 1.8 5) MNC_WRITE_VAR('file', 'Vname', var, bi, bj, myThid)
18 edhill 1.1
19     This is a reasonable start but its inflexible since it isn't easily
20     generalized to grids with dimensions other than [2,3,4] or grids with
21     non-horizontal orientations (eg. vertical slices).
22    
23    
24     Generalizing what we would like to write as "variables defined on 1-D
25     to n-D grids", one can imagine a small number of objects containing
26     all the relevant information:
27    
28     a dimension: [ name, size, units ]
29     a grid: [ name, 1+ dim-ref ]
30     a variable: [ name, units, *1* grid-ref, data ]
31     an attribute: [ name, units, data ]
32     a NetCDF file: [ name, 0+ attr, 0+ grid-ref, 0+ var-ref ]
33    
34     which can then be manipulated (created, associated, destroyed, etc.)
35     using a simple interface such as:
36    
37 edhill 1.8 MNC_INIT( myThid )
38 edhill 1.1
39 edhill 1.8 MNC_FILE_CREATE( myThid, fname )
40     MNC_FILE_OPEN( myThid, fname, itype )
41 edhill 1.1 MNC_FILE_ADD_ATTR_STR( myThid, fname, atname, sval )
42 edhill 1.5 MNC_FILE_ADD_ATTR_DBL( myThid, fname, atname, len, dval )
43     MNC_FILE_ADD_ATTR_REAL(myThid, fname, atname, len, rval )
44     MNC_FILE_ADD_ATTR_INT( myThid, fname, atname, len, ival )
45     MNC_FILE_ADD_ATTR_ANY( myThid, fname, atname, atype, cs,len,dv,rv,iv )
46 edhill 1.1 ...
47     MNC_FILE_READ_HEADER( myThid, fname )
48    
49 edhill 1.8 MNC_DIM_INIT( myThid, fname, dname, dlen )
50 edhill 1.1
51 edhill 1.8 MNC_GRID_INIT( myThid, fname, gname, ndim, dnames )
52 edhill 1.1
53 edhill 1.8 MNC_VAR_INIT_DBL( myThid, fname, gname, vname, units )
54     MNC_VAR_INIT_REAL( myThid, fname, gname, vname, units )
55     MNC_VAR_INIT_INT( myThid, fname, gname, vname, units )
56     MNC_VAR_INIT_ANY( myThid, fname, gname, vname, units, type )
57     MNC_VAR_ADD_ATTR_STR( myThid, fname, vname, atname, sval )
58     MNC_VAR_ADD_ATTR_DBL( myThid, fname, vname, atname, nv, dval )
59 edhill 1.5 MNC_VAR_ADD_ATTR_REAL( myThid, fname, vname, atname, nv, rval )
60 edhill 1.8 MNC_VAR_ADD_ATTR_INT( myThid, fname, vname, atname, nv, ival )
61     MNC_VAR_ADD_ATTR_ANY( myThid, fname, vname, atname, atype, cs,len,dv,rv,iv )
62     MNC_VAR_WRITE_DBL( myThid, fname, vname, var )
63     MNC_VAR_WRITE_REAL( myThid, fname, vname, var )
64     MNC_VAR_WRITE_INT( myThid, fname, vname, var )
65     MNC_VAR_WRITE_ANY( myThid, fname, vname, vtype, dv, rv, iv )
66 edhill 1.1 ...
67 edhill 1.4 MNC_VAR_READ( myThid, fname, vname, var )
68 edhill 1.1
69 edhill 1.9 MNC_FILE_SYNC( myThid, fname )
70 edhill 1.8 MNC_FILE_CLOSE( myThid, fname )
71    
72    
73     Heres a further "convenience wrapper" written on top of the above UI:
74    
75 edhill 1.9 MNC_CW_INIT( myThid, Gtype, Htype, Hsub, Vtype, Ttype, wHalo )
76 edhill 1.8
77 edhill 1.9 with pre-defined - xy - - n
78     combinations: U x c t y
79     'Cen_xy_c_t_Hn' V y i
80     'U_xy_i_t_Hn', Cen
81     'Cor_x_-_-_Hy' Cor
82 edhill 1.8
83 edhill 1.9 MNC_CW_WRITE( myThid,myIter, filebn,bi,bj, Gtype, RX, vname, var )
84     MNC_CW_READ( myThid,myIter, filebn,bi,bj, Gtype, RX, vname, var )
85 edhill 1.1
86 edhill 1.10 MNC_CW_RX_WRITES_YY( myThid, fbname,bi,bj, vtype, indu, var )
87 edhill 1.2
88    
89     To-Do:
90     ======
91    
92 edhill 1.7 1) NAMING -- We should (as much as possible) try to name variables so
93     that they are in agreement with the CF naming conventions.
94    
95     2) UNITS -- as with the names we need to follow conventions
96 edhill 1.6
97 edhill 1.7 3) AM described her "diags" (or "myDiags" or "mDiags") interface
98 edhill 1.6 which should use MNC for output. The data storage idea is similar
99     to the MNC tables-of-indicies approach but also includes one huge
100     double-precision "accumulator" to hold all the temporary values
101     (eg. partial sums for averages, current max/mins):
102    
103     vname ( ni )
104     vlen ( ni )
105 edhill 1.7 vind ( ni ) ------+
106 edhill 1.8 |
107 edhill 1.6
108     vij_diag ( i, j, [...] ) w/ lat/lon indicies
109     vgl_diag ( [...] ) wo/ lat/lon indicies (global)
110 edhill 1.7
111     4) CNH pointed out that grid interpolation needs to be handled
112     "on-the-fly" since pre-processing would result in overly large
113     input files. We need an interpolation API...
114 edhill 1.8
115     5) From the group meeting on 2004/01/21, we need to define
116     "sub-grids" corresponding to:
117    
118     var_name HGRID VGRID TIME
119     ===========================================
120     u U_xy r_c t
121     eta T_xy - t
122     rac T_xy - -
123    
124     And write a convenience wrapper so that users can write variables
125     using just two function calls. JMC and I worked out the
126     following:
127    
128 edhill 1.7

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