# Pencil Code User Meeting 2018 - Boulder

11-15 June 2018
JILA
Europe/Stockholm timezone
The Pencil Code User Meeting is an annual event where both experts and newcomers get together, learn about the code, and work towards improving it. There will also be a few science talks highlighting recent developments in which the Pencil Code played a role.

Most of the sessions can be followed via skype, zoom, or some other means. In order to participate in those, please register were a full participant and indicate this in the comments field in the registration.

Link to previous events: http://pencil-code.nordita.org/meetings.php

# Conclusions of the meeting

Summary of the 14th Pencil Code User Meeting (Boulder 2018)

The meeting ran for a full week of 11-15 June 2018.
Out of the 19 registered participants, 8 were physically present while
the rest was connected via skype or zoom to specific sessions; see
http://INDICO/conferenceDisplay.py?confId=6539
Several of the participants reported on their working experience with
other codes, notably Pluto, Dedalus, Cosmos, CosmoHammer, and Athena.

* Axel presented the updated document "Scientific Usage of the Pencil
Code" which now contains 475 research papers using the Pencil
Code and an additional 68 papers referring to the Pencil Code; see
http://norlx51.nordita.org/~brandenb/tmp/citations/notes.pdf Several
science results we presented as part of this meeting, notably on
accretion in global simulations and in strongly magnetized discs, on
solar and stellar dynamo, the early universe, and super-Chandrasekhar
white dwarfs.
* Matthias reported that the Terms of Reference of the Steering Committee
were accepted by the majority of the owners.
* Wolfgang demonstrated the working of Travis-ci.com. It is now configured
such that every single check-in is being tested at level 2 (~30 tests).
* Axel reported that the special issue for Geophys. Astrophys. Fluid Dyn.
is likely to contain at least 10 papers, of which 2 are currently being
refereed and 8 others ones have been promised. The final deadline for
accepted papers to be included in the special issue is, as previously
announced, 15 January 2019. The two papers are available on the arXiv:
https://arxiv.org/abs/1806.01570
https://arxiv.org/abs/1806.06776
* The Tuesday afternoon session at the National Solar Observatory on
"Major dynamo transitions in the Sun's evolution" was featured by the
Goettingen group and was attended by over 30 people from several
other groups in Boulder (notably the High Altitude Observatory and
the Space Science Institute).
* Axel demonstrated that the remeshing routines worked in the case of
gravitational wave, but he adjusted parts of the manual that referred
to an old cvs repository. (The code had been on github/google-code
for a number of years already.)
* Matthias reported that the Yin-Yang module works, but there may still
be some bugs. Mariangela presented results for the magnetic field, which
look clean, but there seem to be artifacts near the mesh boundaries
that are most evident in the velocity field.
* Matthias and Axel gave an update on the use of 1-sided boundary
conditions and an update on problem of sound waves bouncing back and
forth in a freely moving wagon. Using an idl test, it turned out that
the correct solution can only be obtained at high resolution when the
diffusivity is large enough to resolve shocks.
* Matthias, Johannes Pekkilä, and Maarit gave an update on GPU-acceleration.
A speedup by a factor of 7 was reported. Supercomputers with graphics
cards on each node can now be used.
* Simon reported on the new python suite (Pencilnew), which is now
basically complete. The old one still exists, which may still cause
confusion.
* Guest lectures were given by Nick Featherstone on the Rayleigh code
(a public spherical harmonics code), and by Ben Brown on the Dedalus
code (a public multi-purpose code capable of solving initial value,
boundary value, and eigenvalue problems spectrally and semi-implicitly of
equations that are stated in symbolic form using a python interface).
Ben sympathized with the idea to develop new benchmarks to test
high-order aspects of 3-D codes (turbulence, dynamos, etc).
* Vince discussed the status of the cylindrical selfgravity and Poisson
module. There is currently no z-extent.
* Joern discussed the status of the heatflux & Boris correction in solar
MHD simulations.
* Sayan reported on early universe simulations and Alberto discussed
the status of the gravitational wave module.
* Petri presented various magnetic LES modules. None of them seem to
be safe when confronted with dynamo problems.
* Joern and Matthias gave an update on slope limited diffusion.
There is still a problem with viscous heating. Attempts to fix this
(r74486 of 18 May 2017) resulted in new problems. This change was revoked
on 16 June 2018, but the heating problem is still not addressed.
* Joern urged future User Meeting organizers to fix the time well
in advance. The 2019 meeting could potentially be at Aalto University
(west of Helsinki). Possible time slots would include July 15-19, 22-26,
July 29 - Aug 2, and August 5-9. Another option is still California.

Starts
Ends
Europe/Stockholm
JILA
Foothills Room
University of Colorado, JILA, 10th floor
 https://github.com/pencil-code Link to previous meetings Slides