[GRASS-dev] [GRASS GIS] #429: Add option to disable warnings in modules

GRASS GRASS developer
1

#429: Add option to disable warnings in modules
-------------------------+--------------------------------------------------
Reporter: kyngchaos | Owner: grass-dev@lists.osgeo.org
     Type: enhancement | Status: new
Priority: minor | Milestone: 6.4.0
Component: default | Version: svn-develbranch6
Keywords: | Platform: Unspecified
      Cpu: Unspecified |
-------------------------+--------------------------------------------------
I would like to be able to suppress warning messages in commands, yet keep
messages based on the GRASS_VERBOSE level, especially in raster projection
(r.proj) where is possible to get thousands of "pj_transform() failed:
tolerance condition error" warnings, depending on the projection, that are
expected but clutter the progress output and slow down the process.

I see that G_warning() has a companion G_suppress_warnings(), so this at
least was an intended possibility at one time (but maybe deprecated or
discouraged now?).

--
Ticket URL: <http://trac.osgeo.org/grass/ticket/429&gt;
GRASS GIS <http://grass.osgeo.org>

2

#429: Add option to disable warnings in modules
--------------------------+-------------------------------------------------
  Reporter: kyngchaos | Owner: grass-dev@lists.osgeo.org
      Type: enhancement | Status: new
  Priority: minor | Milestone: 6.4.0
Component: default | Version: svn-develbranch6
Resolution: | Keywords:
  Platform: Unspecified | Cpu: Unspecified
--------------------------+-------------------------------------------------
Comment (by hamish):

Replying to [ticket:429 kyngchaos]:
> I would like to be able to suppress warning messages in
> commands, yet keep messages based on the GRASS_VERBOSE level,
> especially in raster projection (r.proj) where is possible
> to get thousands of "pj_transform() failed: tolerance condition
> error" warnings, depending on the projection, that are expected
> but clutter the progress output and slow down the process.

better: fix the noisy module. e.g.

{{{
  if(!pj_fail_flag)
     G_warning();
  else
     pj_fail_flag = TRUE;
}}}

> I see that G_warning() has a companion G_suppress_warnings(),
> so this at least was an intended possibility at one time (but
> maybe deprecated or discouraged now?).

vaguely discouraged, as it will inadvertently hide important problems, and
you /will/ be bitten by this after some time.

Hamish

--
Ticket URL: <https://trac.osgeo.org/grass/ticket/429#comment:1&gt;
GRASS GIS <http://grass.osgeo.org>

3

#429: Add option to disable warnings in modules
--------------------------+-------------------------------------------------
  Reporter: kyngchaos | Owner: grass-dev@lists.osgeo.org
      Type: enhancement | Status: new
  Priority: minor | Milestone: 6.4.0
Component: default | Version: svn-develbranch6
Resolution: | Keywords:
  Platform: Unspecified | Cpu: Unspecified
--------------------------+-------------------------------------------------
Comment (by kyngchaos):

> better: fix the noisy module.

Well, it's in the GRASS proj library, do_proj.c: pj_do_proj() and
pj_do_transform(), so it'll affect anything that projects coordinates. I
don't see a way to remove it for a single module other than a flag.

{{{
if (ok < 0) {
   G_warning(_("pj_transform() failed: %s"), pj_strerrno(ok));
}
return ok;
}}}

--
Ticket URL: <https://trac.osgeo.org/grass/ticket/429#comment:2&gt;
GRASS GIS <http://grass.osgeo.org>

4

#429: Add option to disable warnings in modules
--------------------------+-------------------------------------------------
  Reporter: kyngchaos | Owner: grass-dev@lists.osgeo.org
      Type: enhancement | Status: new
  Priority: minor | Milestone: 6.4.0
Component: default | Version: svn-develbranch6
Resolution: | Keywords:
  Platform: Unspecified | Cpu: Unspecified
--------------------------+-------------------------------------------------
Comment (by pkelly):

Something about this just doesn't seem quite right to me. What is the
"tolerance condition error" and under what conditions does it appear? Are
you sure it is harmless? It sounds to me like something we should clarify
on the PROJ.4 list, rather than just hiding it.

--
Ticket URL: <http://trac.osgeo.org/grass/ticket/429#comment:3&gt;
GRASS GIS <http://grass.osgeo.org>

5

#429: Add option to disable warnings in modules
--------------------------+-------------------------------------------------
  Reporter: kyngchaos | Owner: grass-dev@lists.osgeo.org
      Type: enhancement | Status: new
  Priority: minor | Milestone: 6.4.0
Component: default | Version: svn-develbranch6
Resolution: | Keywords:
  Platform: Unspecified | Cpu: Unspecified
--------------------------+-------------------------------------------------
Comment (by kyngchaos):

This will happen in any of the perspective/orthographic and related
projections where there are large sections (ie corners) that have no
reverse projection, since GRASS uses a reverse projection to project
rasters.

--
Ticket URL: <http://trac.osgeo.org/grass/ticket/429#comment:4&gt;
GRASS GIS <http://grass.osgeo.org>

6

#429: Add option to disable warnings in modules
--------------------------+-------------------------------------------------
  Reporter: kyngchaos | Owner: grass-dev@lists.osgeo.org
      Type: enhancement | Status: new
  Priority: minor | Milestone: 6.4.0
Component: default | Version: svn-develbranch6
Resolution: | Keywords:
  Platform: Unspecified | Cpu: Unspecified
--------------------------+-------------------------------------------------
Comment (by kyngchaos):

Hmm, the first nowarn toggle missed the correct code... maybe it should go
around the bordwalk() calls (both? 2nd only?)? I still got warnings when
it scans for the extents. But the main row/column loop worked.

So, as a comparison: before this enhancement request, I had a r.proj (LL
to perspective) running for 2 hours and gave up and cancelled it. I
couldn't tell how far it got since the progress was lost in warnings.

With just the main loop with warnings off, r.proj finished projecting the
raster in 10 minutes, and I don't see any missing or corrupt data.

Yes, it is possible that that there could be other issues in other
projections where warnings would be helpful, but if (I know, "if") I see
them I can redo it with warnings. Maybe some known harmless warnings,
like the tolerance condition error warning, could be explicitly ignored in
the nowarn flag, but I suppose we'd have to decide what is harmless, if
possible.

--
Ticket URL: <http://trac.osgeo.org/grass/ticket/429#comment:5&gt;
GRASS GIS <http://grass.osgeo.org>

7

#429: Add option to disable warnings in modules
--------------------------+-------------------------------------------------
  Reporter: kyngchaos | Owner: grass-dev@lists.osgeo.org
      Type: enhancement | Status: new
  Priority: minor | Milestone: 6.4.0
Component: default | Version: svn-develbranch6
Resolution: | Keywords:
  Platform: Unspecified | Cpu: Unspecified
--------------------------+-------------------------------------------------
Comment (by pkelly):

I also like the idea of a flag for r.proj to hide any errors from PROJ.4,
but for implementing it I think it might be better (this would be for
GRASS 7 - too disruptive for 6.x I think) to remove the code in
lib/proj_do_proj.c that prints the error messages as a GRASS warning, and
instead make sure all modules calling pj_do_proj() or pj_do_transform()
check the return value and do what they see fit if it indicates an error
value. They really should be checking the return value at the minute IMHO.

--
Ticket URL: <http://trac.osgeo.org/grass/ticket/429#comment:6&gt;
GRASS GIS <http://grass.osgeo.org>

8

#429: Add option to disable warnings in modules
--------------------------+-------------------------------------------------
  Reporter: kyngchaos | Owner: grass-dev@lists.osgeo.org
      Type: enhancement | Status: new
  Priority: minor | Milestone: 6.4.0
Component: default | Version: svn-develbranch6
Resolution: | Keywords:
  Platform: Unspecified | Cpu: Unspecified
--------------------------+-------------------------------------------------
Comment (by glynn):

Replying to [ticket:429 kyngchaos]:

> I would like to be able to suppress warning messages in commands, yet
keep messages based on the GRASS_VERBOSE level, especially in raster
projection (r.proj) where is possible to get thousands of "pj_transform()
failed: tolerance condition error" warnings, depending on the projection,
that are expected but clutter the progress output and slow down the
process.

The correct solution here is as others have suggested: limit the number of
warnings from a single source rather than disabling them completely.

The main problem with pj_do_proj() and pj_do_transform() is that the same
G_warning() call is used to report any and all error conditions from
pj_transform(). Some may be more serious than others, so printing a fixed
number of warnings could result in harmless warnings being shown but more
serious ones being suppressed.

A more robust solution is to record the last error code, and suppress
multiple consecutive occurrences of the same error. If you get a different
error, you generate a warning for it.

This will still produce a flood if you get alternating errors, but
avoiding that is awkward, requiring e.g. an array containing a flag for
each error code.

> I see that G_warning() has a companion G_suppress_warnings(), so this at
least was an intended possibility at one time (but maybe deprecated or
discouraged now?).

It's a band-aid for library functions which generate too many warnings. I
suggest removing it in 7.0. If there are cases where the library should
normally produce a warning (because it's unrealistic to require
programmers to manually check for rare errors) but cases where it needs to
be disabled, there should either be a "nowarn" flag or a corresponding
function to suppress a specific warning.

The existing usage means that code which uses G_suppress_warnings() around
e.g. G_read_colors() to suppress the "colour support ... missing" warning
(which is harmless; you just get the default rainbow colour table) could
also suppress more significant warnings.

--
Ticket URL: <http://trac.osgeo.org/grass/ticket/429#comment:7&gt;
GRASS GIS <http://grass.osgeo.org>

9

#429: Add option to disable warnings in modules
-------------------------+--------------------------------------------------
Reporter: kyngchaos | Owner: grass-dev@…
     Type: enhancement | Status: new
Priority: minor | Milestone: 6.4.4
Component: Default | Version: svn-develbranch6
Keywords: | Platform: Unspecified
      Cpu: Unspecified |
-------------------------+--------------------------------------------------
Changes (by neteler):

  * milestone: 6.4.0 => 6.4.4

Comment:

See also ticket #383

--
Ticket URL: <http://trac.osgeo.org/grass/ticket/429#comment:8&gt;
GRASS GIS <http://grass.osgeo.org>