Roland, thank you very much for the information. Sorry that I was not able to join the telecon, but Jay informed me about the discussion.
Thanks, Bruno
Il giorno gio 12 nov 2020 alle ore 16:38 Roland Haas rhaas@illinois.edu ha scritto:
Hello Bruno, Jay, (to mark this email as "responded")
Jay brought this up in today's ET call:
http://lists.einsteintoolkit.org/pipermail/users/2020-November/007670.html
and Peter, Zach, I responded:
--8<-- Jay Kalinani: TOV simulation using new Spritz code. When adding a dipolar magnetic field to the star, there is some confusion about the behavior of cctk_time. There's a desire to not store RK intermediate values of cctk_time to cctk_time itself. Zach suggested that a local variable could be defined that simply outputs cctk_iteration*dt if desired. Roland had some comments about scheduling such a routine. --8<--
basically: "this is as designed in case the RHS in has an explicit dependency on time".
Yours, Roland
Hi Erik, those should be internal steps of the Runge-Kutta integrator when going from t to t+dt. Why is the cctk_time changed in those intermediate steps? Shouldn't cctk_time be set only at each iteration in time?
Thanks, Bruno
Il giorno mer 11 nov 2020 alle ore 15:11 Erik Schnetter < schnetter@cct.lsu.edu> ha scritto:
Jay
This intermediate step comes from the time integrator. The Einstein Toolkit usually uses Runge-Kutta type time integrators that perform multiple sub-steps for each time step. These time integrators are provided by the "Methods of Lines" thorn ("MoL"). The respective documentation should have further pointers, and the respective parameter settings should also tell you more. (See also e.g. https://en.wikipedia.org/wiki/Runge–Kutta_methods).
-erik
On Tue, Nov 10, 2020 at 12:20 PM Jay Vijay Kalinani jayvijay.kalinani@phd.unipd.it wrote:
Dear all,
I am trying to perform a magnetised TOV simulation using Einstein
Toolkit and Spritz GRMHD code. In particular, currently I have a
subroutine
that adds a dipolar magnetic field to the TOV star after its initial
data
has been generated via TOVSolver thorn.
Within this subroutine, I have added the following lines that print
the
'cctk_time' value as:
character(len=200) warnline WRITE( warnline, '( "cctk_time: ", g16.7)' ) cctk_time call CCTK_INFO(warnline)
This subroutine is scheduled in HydroBase_Con2Prim after Con2Prim
step.
And I get the following lines in the .out file as:
.........
INFO (TOVSolver): Integrated TOV equation
INFO (TOVSolver): Information about the TOVs used:
INFO (): TOV radius mass bary_mass mass(g) cent.rho rho(cgi)
K K(cgi) Gamma
INFO (): 1 8.12502 1.40016 1.50618 2.78e+33 0.00128 7.92e+14
100 1.45e+05 2
INFO (TOVSolver): Not using old matter initial data
INFO (TOVSolver): Done interpolation.
INFO (Spritz_DipoleAndAtmo): cctk_time: 0.000000
INFO (Spritz_DipoleAndAtmo): Adding a poloidal magnetic field to the
TOV
star on reflevel 0
INFO (Spritz_DipoleAndAtmo): Adding atmo to the TOV star on reflevel
=
'0'
INFO (Spritz_DipoleAndAtmo): cctk_time: 0.000000
Iteration Time | ADMBASE::alp |
HYDROBASE::rho | HYDROBASE::press |
SPRITZ::B_norm
| minimum maximum | minimummaximum | minimum maximum | minimum maximum
0 0.000 | 0.6698612 0.9603815 | 5.827798e-110.0012800 | 0.0000000 0.0001638 | 8.399814e-09 0.0000399
INFO (Spritz_DipoleAndAtmo): cctk_time: 0.3906250E-01
INFO (Spritz_DipoleAndAtmo): cctk_time: 0.3906250E-01
INFO (Spritz_DipoleAndAtmo): cctk_time: 0.7812500E-01
INFO (Spritz_DipoleAndAtmo): cctk_time: 0.7812500E-01
1 0.078 | 0.6698612 0.9603833 | 5.827814e-110.0012799 | 0.0000000 0.0001638 | 8.294987e-09 0.0000395
INFO (Spritz_DipoleAndAtmo): cctk_time: 0.1171875
INFO (Spritz_DipoleAndAtmo): cctk_time: 0.1171875
INFO (Spritz_DipoleAndAtmo): cctk_time: 0.1562500
INFO (Spritz_DipoleAndAtmo): cctk_time: 0.1562500
2 0.156 | 0.6698612 0.9603850 | 5.827829e-110.0012797 | 0.0000000 0.0001638 | 8.294994e-09 0.0000390
..........
The simulation is performed in uniform grid with dx=dy=dz=0.3125,
time::dtfac = 0.25 and HydroBase::timelevels = 2.
As you may see from the output lines, in between iteration 0 which
is at
cctk_time=0.0 and iteration 1 which is at cctk_time=0.078125, there is
an
intermediate time step with 'cctk_time=0.0390625' when the subroutine
is
called.
I was hoping to understand better why this intermediate time step
exists
between two consecutive iterations, and if there is any documentation I could look at.
Any help would be much appreciated.
Thank you very much. Sincerely, Jay Kalinani _______________________________________________ Users mailing list Users@einsteintoolkit.org http://lists.einsteintoolkit.org/mailman/listinfo/users
-- Erik Schnetter schnetter@cct.lsu.edu http://www.perimeterinstitute.ca/personal/eschnetter/ _______________________________________________ Users mailing list Users@einsteintoolkit.org http://lists.einsteintoolkit.org/mailman/listinfo/users
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