Debian specific setup
=====================

`SymPow', as distributed by Debian, runs as any regular executable,
that is to say, not in an esoteric manner: intermediate computing
steps that were meant to be executed `by hand' by end-users are now
launched on the fly. It also comes with a larger set of precomputed
data which are now managed system wide rather than locally.

The user-computed plain data mesh files and their binary counter parts,
are placed by default in the cache directory HOME/.sympow . This default/
historical cache folder can be overridden through the environment variable
SYMPOW_CACHEDIR: the basename of the so passed path is assumed to begin
with `sympow', otherwise the effective path is assumed to be
SYMPOW_CACHEDIR/sympow.

If the cache folder SYMPOW_CACHEDIR (or SYMPOW_CACHEDIR/sympow) does not
exists, then it is created on the fly with respect to permissions and
privileges whenever the following conditions are satisfied:
 (i) it terminates with at least three directory separators (the creation
   is group-centric when the number of separators is greater or equal to six,
   user-centric otherwise);
 (ii) its parent directory exists.
Along the same vain, the default/historical cache directory HOME/.sympow will
be created on the fly if it is nonexistent (the creation is user-centric).

The precomputed plain data mesh files are distributed in /usr/share/sympow;
this default directory can be overridden through the environment variable
SYMPOW_PKGDATADIR. Their binary counter parts, the binary data mesh files,
are created on the fly and stored in the cache directory /var/cache/sympow;
this default directory can be overrident through the environment variable
SYMPOW_PKGCACHEDIR. The scripts effectivelly employed to compute data can be
found in /usr/lib/sympow; this default directory can be overridden through
the environment variable SYMPOW_PKGLIBDIR. Please note that the environment
variables introduced here, viz SYMPOW_{PKGDATADIR,PKGLIBDIR,PKGCACHEDIR},
are meant for advance usage or debugging.

The data in SYMPOW_CACHEDIR{,/sympow} are authoritative.

For minutes details, you want to peruse the associated patches as distributed
within the Debian source ball: d/p/upstream-{system_wide,on_fly_new_data}.patch .

 -- Jerome Benoit <calculus@rezozer.net>  Mon, 26 Dec 2016 14:50:03 +0000