[Paraview] Problem with custom time-aware reader
Stephane PLOIX
stephane.ploix at edf.fr
Fri Sep 11 03:39:37 EDT 2009
Hi Karl,
We had a similar pb to yours : our times are not 1D, but 2D in the sense
that each physical time can be associated to one or several iterations.
What I did was to provide a TimeMode parameter :
If the TimeMode is set the PhysicalTime (the default), then the reader
exposes the available physical times in the request Information pass, and
always provides the last iteration available when requested a given time.
When the time mode is set to Iteration, the user also has to provide the
physical time he want to look at, and then the reader exposes the
available iterations for this given physical time in the information pass,
and outputs the good iteration when asked for.
Just to share ideas...
Stephane
kmorel at sandia.gov
Envoyé par : paraview-bounces at paraview.org
11/09/2009 00:45
A
kkoenig11 at web.de
cc
paraview at paraview.org
Objet
Re: [Paraview] Problem with custom time-aware reader
Actually, we designed the file series reader with the understanding that
time ranges might overlap, but with a different use case in mind. Our
users often have to run simulations far past the mean time to failure of
the platforms they are running on. To handle the problem of the
inevitable crash of the system, the simulation periodically writes out
checkpoint files. When the system fails, the simulation is “backed back”
to the last checkpoint and restarted. As the simulation reruns from this
point, it will recompute some time steps and rewrite out the data for
those times. The file series reader understands that these time steps are
duplicated and picks the one most likely to be correct.
So the problem is that your case excludes this case. If the file series
reader declared an error whenever it encountered multiple versions of the
same time, it would not be reading in the restarted simulation data
correctly. The problem is, your case does not really represent an actual
time series in the physical sense. I can see the utility of looking at
the intermediate solutions, but these intermediate solutions are not a
real progression of events in a physical sense. It is by removing the
intermediate results that you get a progression of actual physical events.
In fact, I can see utility in viewing the data in either way.
So instead, I suggest some workarounds. First, your reader might be able
to sense which iterative intermediate result it is reading and then add
some delta to the time to make the file series reader recognize them as
different times. This is probably the most hack-ish, as, again, these
intermediate results do not really represent a time series (even if you
want them animated as such). Second, you could have a flag in your reader
to ignore time. If your reader does not set the time keys, the file
series reader will treat the files as an ordinary sequence. Third, you
(or I) could add a flag to the file series reader that would force it to
ignore the time in the reader. This flag would be hidden for most
readers, but could be exposed for your reader.
-Ken
On 9/9/09 8:46 AM, "Karl König" <kkoenig11 at web.de> wrote:
Hi Ken,
Sorry to persist, but I found a case that is not properly dealt with by
the class FileSeriesReader in cooperation with the reader you kindly
modified helping me out:
There are cases, though rare, where multiple files can contain identical
time step values. Think about a transient nonlinear solution process
where the linear solver exports its intermediate solutions to disk - all
files within one nonlinear step will contain the same time step value.
There are probably other cases as well.
By fixing bug 8892, you added (among others) these instructions to
Servers/Filters/vtkFileSeriesReader.cxx:
> int vtkFileSeriesReaderTimeRanges::GetAggregateTimeInfo([...])
> {
> [...]
> double timeRange[2];
> timeRange[0] = this->RangeMap.begin()->second
> ->Get(vtkStreamingDemandDrivenPipeline::TIME_RANGE())[0];
> timeRange[1] = (--this->RangeMap.end())->second
> ->Get(vtkStreamingDemandDrivenPipeline::TIME_RANGE())[1];
>
> // Special case: if the time range is a single value, supress it. This
is
> // most likely from a data set that is a single file with no time
anyway.
> // Even if it is not, how much value added is there for a single time
value?
> if (timeRange[0] >= timeRange[1])
> {
> outInfo->Remove(vtkStreamingDemandDrivenPipeline::TIME_RANGE());
> outInfo->Remove(vtkStreamingDemandDrivenPipeline::TIME_STEPS());
> return 1;
> }
which lead to the situation that only the last file of a file series is
loaded by readers depending on class FileSeriesReader if the files
contain non-unique time step values. You can test it with the attached
reader plugin and the file series sampleinputfiles/sametimes*.foo.
You'll notice on STDOUT that only sametimes9.foo, the last file, is
loaded.
I'd like to propose a patch that warns the user for such a file series
and falls back to fake time step values. I'm not sure about implications
for animation functions, though, I'm afraid. But having applied the
patch, one can step through sametimes*.foo as well.
(Actually, willing to support the same-time-step-values-in-all-files
case is the reason why I went through the trouble to have my own book
keeping in my reader.)
Karl
----- Original Message -----
From: "Moreland, Kenneth" <kmorel at sandia.gov>
To: Karl König <kkoenig11 at web.de>
CC: "paraview at paraview.org" <paraview at paraview.org>
Sent: Sonntag, 6. September 2009 18:20:26
Subject: [Paraview] Problem with custom time-aware reader
> OOPS! STOP! BACK UP! I looked at your code too quickly, misunderstood
> what you were doing, and gave totally the wrong advise. Please ignore
> everything I said before.
>
> If you are using the file series reader, then your reader should be
> completely ignorant of any file series. It should read in only the file
> it is given, and if that file changes then it should ignore whatever
> file it was previously given. Therefore, the problem with your reader
> is that it is trying to collect time information over all the files.
> That is the job of the file series reader and as a result it is fouling
> up the operation of the file series reader.
>
> So, what your reader should do is read in the time value in the file it
> is given, set the TIME_STEPS key to ONLY that time value and set the
> TIME_RANGE to be only that range. Attached is a modified version of
> your reader example that has all that time series management stripped
> out. The resulting code is much smaller and actually works.
>
> Specifically what was happening was that by the time RequestInformation
> was called on the last time step, your reader had collected information
> about all the time steps and returned all the time steps in all the
> files. The file series reader thought you meant that the last file
> contained all those time steps (some file formats do contain multiple
> time steps in a single file). Because your reader said that the last
> file contained all the time steps, the file series reader was using that
> last file for all the time steps.
>
> -Ken
>
>
> On 9/3/09 11:24 PM, "Karl König" <kkoenig11 at web.de> wrote:
>
> Hi Ken,
>
> Thanks again for your input.
>
> > You have the basic idea. The seg fault is probably happening
because
> > the destructor of you class is trying to free the pointer you set
> to it,
> > which is probably actually pointing to some spot on the stack.
> >
> > You are probably not seeing this mapping/lookup in the VTK IO
classes
> > because you are looking at classes that do not directly support
time
> > (such as the legacy readers and XML readers). Those readers read
> > exactly one file with one time step in it. ParaView has a magic
meta
> > reader called a FileSeriesReader that takes a real reader and a
> > collection of files and multiplexes the files to the reader based
> on the
> > time.
> >
> > In retrospect, this is probably an easier way to go (assuming your
> final
> > reader is a file series like this). Documentation on using the
> > FileSeriesReader is on the Wiki at
> >
> >
http://www.paraview.org/Wiki/Restarted_Simulation_Readers#Customized_Restart_Reader
>
> I've been aware of that page. In fact, FooReader.xml and
> FooReaderGUI.xml of the tarball I posted already did make use of the
> FileSeriesReader. Together with calling
> outInfo->Set(vtkStreamingDemandDrivenPipeline::TIME_STEPS(), ...)
> outInfo->Set(vtkStreamingDemandDrivenPipeline::TIME_RANGE(), ...)
> in RequestInformation it is responsible for inspecting all files of
the
> series between selecting them in the file open dialog and appearing
of
> the Apply button.
>
> Anyway, I'll try to use again the mapping time step value -> file
name
> and iron out the segfault on deletion of the reader object.
>
> I'll post the solution in case I can work it out and someone is
> interested.
>
> Karl
>
>
>
>
>
> **** Kenneth Moreland
> *** Sandia National Laboratories
> ***********
> *** *** *** email: kmorel at sandia.gov
> ** *** ** phone: (505) 844-8919
> *** web: http://www.cs.unm.edu/~kmorel
>
**** Kenneth Moreland
*** Sandia National Laboratories
***********
*** *** *** email: kmorel at sandia.gov
** *** ** phone: (505) 844-8919
*** web: http://www.cs.unm.edu/~kmorel
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