/[MITgcm]/MITgcm/pkg/mnc/README.txt
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Revision 1.9 - (hide annotations) (download)
Tue Jan 27 05:47:32 2004 UTC (20 years, 4 months ago) by edhill
Branch: MAIN
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 o first steps towards a "convenience wrapper" for pre-defined grid types
 o small clean-ups

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 1.2
87    
88     To-Do:
89     ======
90    
91 edhill 1.7 1) NAMING -- We should (as much as possible) try to name variables so
92     that they are in agreement with the CF naming conventions.
93    
94     2) UNITS -- as with the names we need to follow conventions
95 edhill 1.6
96 edhill 1.7 3) AM described her "diags" (or "myDiags" or "mDiags") interface
97 edhill 1.6 which should use MNC for output. The data storage idea is similar
98     to the MNC tables-of-indicies approach but also includes one huge
99     double-precision "accumulator" to hold all the temporary values
100     (eg. partial sums for averages, current max/mins):
101    
102     vname ( ni )
103     vlen ( ni )
104 edhill 1.7 vind ( ni ) ------+
105 edhill 1.8 |
106 edhill 1.6
107     vij_diag ( i, j, [...] ) w/ lat/lon indicies
108     vgl_diag ( [...] ) wo/ lat/lon indicies (global)
109 edhill 1.7
110     4) CNH pointed out that grid interpolation needs to be handled
111     "on-the-fly" since pre-processing would result in overly large
112     input files. We need an interpolation API...
113 edhill 1.8
114     5) From the group meeting on 2004/01/21, we need to define
115     "sub-grids" corresponding to:
116    
117     var_name HGRID VGRID TIME
118     ===========================================
119     u U_xy r_c t
120     eta T_xy - t
121     rac T_xy - -
122    
123     And write a convenience wrapper so that users can write variables
124     using just two function calls. JMC and I worked out the
125     following:
126    
127 edhill 1.7

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