GACK! Point isn't on grid!

[Vitor Silva]

When running any of the calculators, it's quite common in running into an error in which messages like the following fill the terminal:

DEBUG:root:GACK! at col 4 row 0
DEBUG:root:Point at 15.64 38.01 isnt on grid
DEBUG:root:GACK! at col 4 row 1
DEBUG:root:Point at 15.64 38.05 isnt on grid
DEBUG:root:GACK! at col 4 row 2
DEBUG:root:Point at 15.64 38.09 isnt on grid
DEBUG:root:GACK! at col 4 row 3
DEBUG:root:Point at 15.64 38.13 isnt on grid
DEBUG:root:GACK! at col 4 row 4
DEBUG:root:Point at 15.64 38.17 isnt on grid
DEBUG:root:GACK! at col 4 row 5
DEBUG:root:Point at 15.64 38.21 isnt on grid

This is a very old error that should be fixed since when using very large regions, hundreds of these warnings are displayed.

[Mattia Barbon (mattia.barbon)]

Can be reproduce using

    ./bin/openquake --config_file=smoketests/nshmp-california-fault/config.gem

[Mattia Barbon (mattia.barbon)]

It's a floating point rounding problem; putting a breakpoint on the line were it prints the GACK:

(Pdb) self.region.upper_right_corner.longitude
-118.18
(Pdb) self.region.upper_left_corner.longitude
-118.3
# region width
(Pdb) self.region.upper_right_corner.longitude - self.region.upper_left_corner.longitude
0.11999999999999034
# number of columns in the region
(Pdb) (self.region.upper_right_corner.longitude - self.region.upper_left_corner.longitude)/self.cell_size
5.999999999999517
# coordinate of the 6-th column:
(Pdb) self.region.upper_left_corner.longitude + 6 * 0.02
-118.17999999999999

which is slightly more than region right border -> the point is outside the region.

I think the correct solution is applying round_float() to the temporary Point() constructed for bounds checking.

By the way, there are some other shapes objects where round_float() is not used.

[Mattia Barbon (mattia.barbon)]

Pull request https://github.com/gem/openquake/pull/493

[Mattia Barbon (mattia.barbon)]

Vitor: there are some other configurations that still print the warning; for example, the one linked in #838983:

REGION_VERTEX = 38.30, 15.48, 38.30, 15.63, 38.01, 15.63, 38.01, 15.48
REGION_GRID_SPACING = 0.05

here the region width (38.01 -> 38.30 = 0.29 is not an exact multiple of 0.05).
In this case should OQ just silently use: 38.01, 38.06, ... 38.26 or should there be some kind of warning to the user (maybe not repeated for each point...)?

[John Tarter (toh2)]

These 2 bugs are needed to be completed before this Gagk bug can be closed, due to incomplete features

https://bugs.launchpad.net/openquake/+bug/809410
https://bugs.launchpad.net/openquake/+bug/856323

[John Tarter (toh2)]

Awaiting input from Vitor

[beatpanic (kpanic)]

pull request here: https://github.com/gem/openquake/pull/560

[Paul Henshaw (paul-sl-henshaw)]

Following rename, PR urls are:

https://github.com/gem/oq-engine/pull/560
https://github.com/gem/oq-engine/pull/493