[Users] About cctk_time

[Jay Vijay Kalinani]

Thank you so much for the clarification!

Sincerely,
Jay

On Wednesday, 11 November 2020, Erik Schnetter <schnetter at cct.lsu.edu>
wrote:

> 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 at 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 |      minimum
> maximum |      minimum      maximum |      minimum      maximum
> >
> > ------------------------------------------------------------
> -----------------------------------------------------------------------
> >
> >         0     0.000 |    0.6698612    0.9603815 | 5.827798e-11
> 0.0012800 |    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-11
> 0.0012799 |    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-11
> 0.0012797 |    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 at einsteintoolkit.org
> > http://lists.einsteintoolkit.org/mailman/listinfo/users
>
>
>
> --
> Erik Schnetter <schnetter at cct.lsu.edu>
> http://www.perimeterinstitute.ca/personal/eschnetter/
>
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