What do HEC and FEC refer to in the Calibre transcript?

Version 1

    The "Calibre Verification User's Manual" shows that when a layer is generated in the Calibre executive module, the operation generating it is decompiled and statistics about the generated layer are printed. For example, in hierarchical Calibre applications, the transcript may look something like this:


    nplus = sdm NOT ppm


    nplus (HIER TYP=1 CFG=1 HGC=4578 FGC=316325 HEC=137654 FEC=37475542 VHC=F VPC=F)

    CPU TIME = 4 REAL TIME = 4 LVHEAP = 27/31/31 OPS COMPLETE = 34 OF 589 ELAPSED TIME = 20


    HGC is the number of objects on the layer counted hierarchically, that is, once per cell.


    FGC is an estimated number of flat objects on the layer, computed by multiplying, for each cell, the number of objects in the cell on the by the total number of flat placements of the cell in the hierarchy, and then adding this together for all the cells. It is an estimate in the sense that no inter-cell merging of geometry occurs when making this calculation. The "objects" are polygons for original and derived polygon layers, edges for derived edge layers, and edge clusters for derived error layers.


    For original and derived polygon layers, HEC is the actual total number of edges on the polygons counted by HGC. For derived edge layers, HEC is identical to HGC. For derived error layers, HEC is the total number of individual edges on the edge clusters counted by HGC.


    FEC is computed from HEC in the same way that FGC is computed from HGC.


    For polygon layers, HEC can be a better measure of the actual geometric size or density of a layer than HGC, since a polygon with N edges is only counted once in HGC, regardless of the size of N.



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