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API Discussions: |
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================ |
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As discussed in our group meeting of 2003-12-17 (AJA, CNH, JMC, AM, |
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PH, EH3), the NetCDF interface should resemble the following FORTRAN |
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subroutines: |
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1) "stubs" of the form: MNC_WV_[G|L]2D_R[S|L] () |
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2) MNC_INIT_VGRID( 'V_GRID_TYPE', nx, ny, nz, zc, zg ) |
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1 1 |
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3) MNC_INIT_HGRID( 'H_GRID_TYPE', nx, ny, xc, yc, xg, yg ) |
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4) MNC_INIT_VAR( 'file', 'Vname', 'Vunits', 'H_GTYPE', 'V_GTYPE', PREC, FillVal ) |
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5) MNC_WRITE_VAR( 'file', 'Vname', var, bi, bj, myThid ) |
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This is a reasonable start but its inflexible since it isn't easily |
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generalized to grids with dimensions other than [2,3,4] or grids with |
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non-horizontal orientations (eg. vertical slices). |
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Generalizing what we would like to write as "variables defined on 1-D |
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to n-D grids", one can imagine a small number of objects containing |
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all the relevant information: |
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a dimension: [ name, size, units ] |
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a grid: [ name, 1+ dim-ref ] |
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a variable: [ name, units, *1* grid-ref, data ] |
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an attribute: [ name, units, data ] |
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a NetCDF file: [ name, 0+ attr, 0+ grid-ref, 0+ var-ref ] |
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which can then be manipulated (created, associated, destroyed, etc.) |
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using a simple interface such as: |
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MNC_INIT( myThid ) |
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MNC_FILE_CREATE( myThid, fname ) |
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MNC_FILE_OPEN( myThid, fname, itype ) |
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MNC_FILE_ADD_ATTR_STR( myThid, fname, atname, sval ) |
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MNC_FILE_ADD_ATTR_DBL( myThid, fname, atname, len, dval ) |
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MNC_FILE_ADD_ATTR_REAL(myThid, fname, atname, len, rval ) |
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MNC_FILE_ADD_ATTR_INT( myThid, fname, atname, len, ival ) |
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MNC_FILE_ADD_ATTR_ANY( myThid, fname, atname, atype, cs,len,dv,rv,iv ) |
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... |
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MNC_FILE_READ_HEADER( myThid, fname ) |
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MNC_DIM_INIT( myThid, fname, dname, dunits, dlen ) |
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MNC_GRID_INIT( myThid, fname, gname, ndim, dnames ) |
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MNC_GRID_SET_LL( myThid, fname, gname, type, lats, lons ) |
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MNC_VAR_INIT_DBL( myThid, fname, gname, vname, units ) |
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MNC_VAR_INIT_REAL( myThid, fname, gname, vname, units ) |
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MNC_VAR_INIT_INT( myThid, fname, gname, vname, units ) |
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MNC_VAR_INIT_ANY( myThid, fname, gname, vname, units, type ) |
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MNC_VAR_ADD_ATTR_STR( myThid, fname, vname, atname, sval ) |
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MNC_VAR_ADD_ATTR_DBL( myThid, fname, vname, atname, nv, dval ) |
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MNC_VAR_ADD_ATTR_REAL( myThid, fname, vname, atname, nv, rval ) |
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MNC_VAR_ADD_ATTR_INT( myThid, fname, vname, atname, nv, ival ) |
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MNC_VAR_ADD_ATTR_ANY( myThid, fname, vname, atname, atype, cs,len,dv,rv,iv ) |
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MNC_VAR_WRITE_DBL( myThid, fname, vname, var ) |
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MNC_VAR_WRITE_REAL( myThid, fname, vname, var ) |
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MNC_VAR_WRITE_INT( myThid, fname, vname, var ) |
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MNC_VAR_WRITE_ANY( myThid, fname, vname, vtype, dv, rv, iv ) |
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... |
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MNC_VAR_READ( myThid, fname, vname, var ) |
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MNC_FILE_CLOSE( myThid, fname ) |
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The above interface is powerful yet easy to use (easier than the |
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entire NetCDF interface) since it helps the user keep track of the |
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associations between files, "grids", variables, and dimensions. |
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To-Do: |
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====== |
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1) NAMING -- We should (as much as possible) try to name variables so |
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that they are in agreement with the CF naming conventions. |
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2) UNITS -- as with the names we need to follow conventions |
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3) AM described her "diags" (or "myDiags" or "mDiags") interface |
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which should use MNC for output. The data storage idea is similar |
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to the MNC tables-of-indicies approach but also includes one huge |
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double-precision "accumulator" to hold all the temporary values |
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(eg. partial sums for averages, current max/mins): |
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vname ( ni ) |
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vlen ( ni ) |
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vind ( ni ) ------+ |
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| |
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vij_diag ( i, j, [...] ) w/ lat/lon indicies |
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vgl_diag ( [...] ) wo/ lat/lon indicies (global) |
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4) CNH pointed out that grid interpolation needs to be handled |
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"on-the-fly" since pre-processing would result in overly large |
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input files. We need an interpolation API... |
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