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New IMEX integrator #612

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New IMEX integrator #612

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6eb7c2b
Update driver.cpp
wisYue Sep 7, 2024
12a3122
Update driver.hpp
wisYue Sep 7, 2024
f36fe03
Update driver.cpp
wisYue Oct 29, 2024
e920877
Update ion-neutral_tasks.cpp
wisYue Oct 29, 2024
9d02b91
Merge branch 'IAS-Astrophysics:main' into main
wisYue Oct 29, 2024
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48 changes: 45 additions & 3 deletions src/driver/driver.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -165,8 +165,8 @@ Driver::Driver(ParameterInput *pin, Mesh *pmesh, Real wtlim, Kokkos::Timer* ptim
nimp_stages = 3;
nexp_stages = 2;
cfl_limit = 1.0;
gam0[0] = 0.0;
gam1[0] = 1.0;
gam0[0] = 1.0;
gam1[0] = 0.0;
beta[0] = 1.0;

gam0[1] = 0.5;
Expand All @@ -185,6 +185,48 @@ Driver::Driver(ParameterInput *pin, Mesh *pmesh, Real wtlim, Kokkos::Timer* ptim
a_twid[2][1] = 0.25;
a_twid[2][2] = 0.25;
a_impl = 0.5;
} else if (integrator == "imex2+") {
// IMEX(4,3,2): Krapp et al. (2024, arXiv:2310.04435), Eq.30.
// three-stage explicit, four-stage implicit, second-order ImEx
// the first two implicit stages are added for adapting Athenak's overall architecture
// Note explicit steps may not reduce to RK2 based on the parameters chosen
nimp_stages = 4;
nexp_stages = 3;
cfl_limit = 1.0;
gamma = 1.707106781186547; //1+1/sqrt(2)
gam0[0] = 1.0;
gam1[0] = 0.0;
beta[0] = gamma;

gam0[1] = (2.0*gamma-1.0)/(2.0*gamma*gamma);
gam1[1] = (1.0-(2.0*gamma-1.0)/(2.0*gamma*gamma));
beta[1] = 1.0/(2.0*gamma);

gam0[2] = 1.0;
gam1[2] = 0.0;
beta[2] = 0.0;

a_twid[0][0] = 0.0;
a_twid[0][1] = 0.0;
a_twid[0][2] = 0.0;
a_twid[0][3] = 0.0;

a_twid[1][0] = 0.0;
a_twid[1][1] = 0.0;
a_twid[1][2] = 0.0;
a_twid[1][3] = 0.0;

a_twid[2][0] = 0.0;
a_twid[2][1] = 0.0;
a_twid[2][2] = (1.0-2.0*gamma*gamma)/2.0/gamma;
a_twid[2][3] = 0.0;

a_twid[3][0] = 0.0;
a_twid[3][1] = 0.0;
a_twid[3][2] = 0.0;
a_twid[3][3] = 0.0;

a_impl = gamma;
} else if (integrator == "imex3") {
// IMEX-SSP3(4,3,3): Pareschi & Russo (2005) Table VI.
// three-stage explicit, four-stage implicit, third-order ImEx
Expand Down Expand Up @@ -258,7 +300,7 @@ Driver::Driver(ParameterInput *pin, Mesh *pmesh, Real wtlim, Kokkos::Timer* ptim
} else {
std::cout << "### FATAL ERROR in " << __FILE__ << " at line " << __LINE__
<< std::endl << "integrator=" << integrator << " not implemented. "
<< "Valid choices are [rk1,rk2,rk3,imex2,imex3]." << std::endl;
<< "Valid choices are [rk1,rk2,rk3,imex2,imex2+,imex3]." << std::endl;
exit(EXIT_FAILURE);
}
}
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1 change: 1 addition & 0 deletions src/driver/driver.hpp
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Expand Up @@ -44,6 +44,7 @@ class Driver {
Real delta[4]; // weights for updating the intermediate stage (u1)
Real a_twid[4][4], a_impl; // matrix elements for implicit stages in ImEx
Real cfl_limit; // maximum CFL number for integrator
Real gamma; // gamma value for the IMEX_new integrator
Kokkos::Timer* pwall_clock_; // timer for tracking the wall clock
Real wall_time;

Expand Down
21 changes: 18 additions & 3 deletions src/ion-neutral/ion-neutral_tasks.cpp
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Expand Up @@ -185,9 +185,24 @@ TaskStatus IonNeutral::ImpRKUpdate(Driver *pdriver, int estage) {
// equations for ion-neutral drag.
// Only required for istage = (1,2,3,[4])
if (estage < pdriver->nexp_stages) {
Real gamma_adt = drag_coeff*(pdriver->a_impl)*(pmy_pack->pmesh->dt);
Real xi_adt = ionization_coeff*(pdriver->a_impl)*(pmy_pack->pmesh->dt);
Real alpha_adt = recombination_coeff*(pdriver->a_impl)*(pmy_pack->pmesh->dt);
Real gamma_adt;
Real xi_adt;
Real alpha_adt;

// Condition to set gamma_adt, xi_adt, and alpha_adt to zero
if (istage < 3 && pdriver->integrator == "imex2+") {
gamma_adt = 0.0;
xi_adt = 0.0;
alpha_adt = 0.0;
} else {
gamma_adt = drag_coeff * (pdriver->a_impl) * (pmy_pack->pmesh->dt);
xi_adt = ionization_coeff * (pdriver->a_impl) * (pmy_pack->pmesh->dt);
alpha_adt = recombination_coeff * (pdriver->a_impl) * (pmy_pack->pmesh->dt);
}

//Real gamma_adt = drag_coeff*(pdriver->a_impl)*(pmy_pack->pmesh->dt);
//Real xi_adt = ionization_coeff*(pdriver->a_impl)*(pmy_pack->pmesh->dt);
//Real alpha_adt = recombination_coeff*(pdriver->a_impl)*(pmy_pack->pmesh->dt)
auto ui = pmhd->u0;
auto un = phyd->u0;
par_for("imex_imp",DevExeSpace(),0,nmb1,0,(n3-1),0,(n2-1),0,(n1-1),
Expand Down
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