[GRASS-dev] Weird bug in r.sun: command hangs forever for some day of the year

[Pierre Roudier]

Hi,

Just bumped into the weirdest bug in r.sun on GRASS 7.4 as installed from
the Ubuntu repository.

I am using r.sun in Mode 2 to compute the daily average global radiation.
The GRASS location is using EPSG:3031: this is data over the entire
Antarctica.

For some specific days, that seem to be in winter, when most of the
continent doesn't recieve any solar radiation, the command would hang
forever at 9%:

For example I had to kill this command:

[Raster MASK present]
GRASS 7.4.0 (modis_lst_2015):/media/pierre/1TB_ext4/code > time r.sun
elev=dem_1k aspect=aspect_1k slope=slope_1k day=159 glob_rad=glob_rad_159
--o --verbose
Number of threads <1>
Mode 2: integrated daily irradiation for a given day of the year
Using Linke constant: 3.000000
Using albedo constant: 0.200000
Using slope map <slope_1k>
Using aspect map <aspect_1k>
^C 9%

But for the day before and the day after the command was successful in less
than a minute:

GRASS 7.4.0 (modis_lst_2015):/media/pierre/1TB_ext4/code > time r.sun
elev=dem_1k aspect=aspect_1k slope=slope_1k day=160 glob_rad=glob_rad_160
--o --verbose
Number of threads <1>
Mode 2: integrated daily irradiation for a given day of the year
Using Linke constant: 3.000000
Using albedo constant: 0.200000
Using slope map <slope_1k>
Using aspect map <aspect_1k>
 100%

real    0m30.019s
user    0m29.602s
sys    0m0.372s

It also happened on day 151... I'm a bit stuck, so any pointers would be
appreciated.

Cheers,

Pierre
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