[Users] About cctk_time

[Jay Vijay Kalinani]

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
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