[GRASS-dev] r.series with file option - too many files open

[Veronica Andreo]

Hi all,

2018-01-15 20:11 GMT+01:00 Markus Neteler <neteler at osgeo.org>:

> On Mon, Jan 15, 2018 at 5:27 PM, Paulo van Breugel
> <p.vanbreugel at gmail.com> wrote:
> > On 1/15/18 4:39 PM, Markus Metz wrote:
> ...
> >> the manual is wrong:
> >> Use the file option to analyze large amount of raster maps without
> hitting
> >> open files limit and the size limit of command line arguments.
> >>
> >> must be
> >> Use the -z flag to analyze large amount of raster maps without hitting
> open
> >> files limit and the file option to avoid hitting the size limit of
> command
> >> line arguments.
> >
> > Ah, yes, I totally forgot about that flag. Thanks (also Anna and
> Veronica).
> > Perhaps somebody with write permission can correct his in the manual
> page?
>
> Done in r72081: please verify. I think it could still be better.
> https://trac.osgeo.org/grass/changeset/72081
>

AFAIU, the file option does not necessarily make the process slower (it
just replaces a list of comma separated maps in a command by a file), it is
the -z flag that does that, because it will open and close files once and
again, instead of keeping them open (Am I right, @markusM?)

Moreover, I checked r.hants and r.series.lwr, which are based on r.series
and have the same file option and -z flag. They all have different wording.
Maybe we could agree here on the 3 of them. From my understanding, they are
not entirely correct. Here the text snippets:

r.hants:
"Use the *file* option to analyze large amount of raster maps without
hitting open files limit and the size limit of command line arguments. The
computation is slower than with the *input* option method. For every single
row in the output map(s) all input maps are opened and closed. The amount
of RAM will rise linearly with the number of specified input maps. The
input and file options are mutually exclusive. The option *input* is a
comma separated list of raster map names and the option *file* is a text
file with a new line separated list of raster map names. Note that the
order of maps in one option or the other is very important."

r.series.lwr:
"Use the *-z* flag to analyze large amounts of raster maps without hitting
the open files limit and the size limit of command line arguments. This
will however increase the processing time. For every single row in the
output map(s) all input maps are opened and closed. The amount of RAM used
will rise linearly with the number of specified input maps.The input and
file options are mutually exclusive. Input is a text file with a new line
separated list of raster map names"

I can change them accordingly once we understand correctly the effect of
both file option and -z flag. Which other modules share this -z flag?

best,
Vero
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