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 < > [email protected]> 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 > > <[email protected]> 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 > > > [email protected] > > > http://lists.einsteintoolkit.org/mailman/listinfo/users > > > > > > > > -- > > Erik Schnetter <[email protected]> > > http://www.perimeterinstitute.ca/personal/eschnetter/ > > _______________________________________________ > > Users mailing list > > [email protected] > > http://lists.einsteintoolkit.org/mailman/listinfo/users > > > > -- My email is as private as my paper mail. 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