The Binary jobname.grp File
The binary jobname.grp file
When a group is read from an ascii file, or created interactively in a D3PLOT session, the information is stored in a binary " jobname .grp" file. There are two reasons for this:
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D3PLOT permits an unlimited number of groups, so storing this information
in memory could become expensive. Storing each group in an ascii file would
be possible, but the processes of agglomerating data to write this file, and
then deconstructing it prior to re-reading and use are both time-consuming
and this would make the editing and use of groups unacceptably slow. The binary
".grp" file contains group information organised in a model-specific
way that is compact and very fast to read and write, making it a much better
solution for storage and editing.
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You are not required to write ascii groups files when a D3PLOT session terminates,
so keeping the binry ".grp" file means that group information is
remembered if the model is subsequently reopened in a later D3PLOT session.
What happens to stored groups in the jobname.grp file when an ascii groups file is read?
When an ascii groups file (group nnn .asc) is read, either manually or automatically when a model is opened, its contents are read and stored. If it contains a group id that is currently defined in a binary jobname.grp file then the contents of the ascii file will overwrite (ie supersede) the contents of the binary file, becoming the current definition of group #id. Any new group ids not in the binary file are added to it, but existing groups in the binary file not present in the ascii one are not deleted.
The "-no_group" command-line option does not influence the reading of binary jobname.grp files.
The " -no_group " command-line option (and the " read_asc_file " preference) do not affect the reading of any existing binary jobname .grp file when a model is opened. So these options can be used to prevent ascii group file definitions superseding groups remembered from earlier D3PLOT sessions using this model.