[MBDyn-users] improvement ideas for 1.3.15

Rix, Patrick Patrick.Rix at repower.de
Wed Mar 24 08:49:14 CET 2010


..O.K. we'll wait for 1.3.15 probably having the "time step width driven" - option for the output meter.

Two other points for improvement concerning the NetCDF output came into my mind:

I'd like to propose adding a data type switch to the "output results:" - card allowing the user to choose between DOUBLE and FLOAT, e.g.:

     "output results : netcdf , [double | float ] ;"

Right now double (i.e. 8-byte floating point values) is the only supported data type for NetCDF output, which might be influenced by MBDyn's internal double precision. But for time series output I think a 4-byte float data type would be pretty sufficient in terms of number range and precision for most problems. Using float values instead of doubles would halve the amount of required disk space (which can be significant for larger models and/or long simulations) without a significant loss in precision and I think this would impose only minor and relatively simple code changes.

The second suggestion is to rename the time track variable "run.time" in just only "time"  and change its data structure from "(time, vec1)" to only "(time)", so having a variable  "time(time)"  instead of  "run.time(time,vec1)"  , defining the same 1D-array structure. This would also hold for other 1D-data series: e.g.  "run.timestep( time )" is exactly the same as "run.timestep(time , vec1)" ,so the "vec1" information is more or less dispensible.
Having a variable  "time(time)"  has advantages for many (3rd party) NetCDF tools (e.g. plotting tools like ncbrowse, andx, intel array viewer, VisIt, ParaView, etc.) as when finding a variable "time(time)" these tools automatically understand the time dependency of the other time series data in the file (most of them are defined as 2D-array-structures containing time series of 3-comp.vectors, e.g. "node.struct.1.X( time, vec3 )" ).
This slight change would have the advantage of easier making XY plots of time series when using the tools mentioned above.
Right now the time track is not detected correctly resulting in plots having the time step index as X-axis instead of the simulation time in seconds.

What do you think of these ideas ? Is it possible and worhty to add them too ?

Best regards,

-----Ursprüngliche Nachricht-----
Von: masarati at aero.polimi.it [mailto:masarati at aero.polimi.it]
Gesendet: Dienstag, 23. März 2010 22:23
An: Rix, Patrick
Betreff: Re: ..the official release 1.3.14

> Hi Pierangelo,
> ..I just wanted to ask if you can add to the next official release the
> possibility of having a "time-step-width" - controlled output meter, i.e.
> the option to have output at every time step reaching or exceeding the
> next (virtual) output time mark for "const. time stepped" output.
> This would be particularly useful when desiring a relatively coarse output
> rate while simulating with either variable time step strategy or with a
> very small const. time step as this could avoid a lot of undesired output
> volume unnecessarily blocking disk space. And it would make a resampling
> post processing step dispensable which would save some time in the data
> analysis process.
> If it is not a big deal to implement it, it would be great if you can add
> it to the 1.3.14 release.


it's on my todo list.  It's probably not a big deal, but right now I
can't: I'm on a business trip for a meeting that will last until the end
of the week.  1.3.14 has been out for a week so far, so I can't modify it.
 It'll be for the next release.  I'm getting to the "release early,
release often" model...

Cheers, p.

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