Files
astaroth/acc/mhd_solver/stencil_process.sps

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Scheme

// Declare uniforms (i.e. device constants)
uniform Scalar cs2_sound;
uniform Scalar nu_visc;
uniform Scalar cp_sound;
uniform Scalar cv_sound;
uniform Scalar mu0;
uniform Scalar eta;
uniform Scalar gamma;
uniform Scalar zeta;
uniform Scalar dsx;
uniform Scalar dsy;
uniform Scalar dsz;
uniform Scalar lnT0;
uniform Scalar lnrho0;
uniform int nx_min;
uniform int ny_min;
uniform int nz_min;
uniform int nx;
uniform int ny;
uniform int nz;
Vector
value(in VectorField uu)
{
return (Vector){value(uu.x), value(uu.y), value(uu.z)};
}
#if LUPWD
Scalar
upwd_der6(in VectorField uu, in ScalarField lnrho)
{
Scalar uux = fabs(value(uu).x);
Scalar uuy = fabs(value(uu).y);
Scalar uuz = fabs(value(uu).z);
return (Scalar){uux*der6x_upwd(lnrho) + uuy*der6y_upwd(lnrho) + uuz*der6z_upwd(lnrho)};
}
#endif
Matrix
gradients(in VectorField uu)
{
return (Matrix){gradient(uu.x), gradient(uu.y), gradient(uu.z)};
}
Scalar
continuity(in VectorField uu, in ScalarField lnrho) {
return -dot(value(uu), gradient(lnrho))
#if LUPWD
//This is a corrective hyperdiffusion term for upwinding.
+ upwd_der6(uu, lnrho)
#endif
- divergence(uu);
}
#if LSINK
Vector
sink_gravity(int3 globalVertexIdx){
Vector force_gravity;
const Vector grid_pos = (Vector){(globalVertexIdx.x - nx_min) * dsx,
(globalVertexIdx.y - ny_min) * dsy,
(globalVertexIdx.z - nz_min) * dsz};
const Scalar sink_mass = DCONST_REAL(AC_M_sink);
const Vector sink_pos = (Vector){DCONST_REAL(AC_sink_pos_x),
DCONST_REAL(AC_sink_pos_y),
DCONST_REAL(AC_sink_pos_z)};
const Scalar distance = length(grid_pos - sink_pos);
const Scalar soft = DCONST_REAL(AC_soft);
const Scalar gravity_magnitude = (AC_G_const * sink_mass) / pow(((distance * distance) + soft*soft), 1.5);
const Vector direction = (Vector){(sink_pos.x - grid_pos.x) / distance,
(sink_pos.y - grid_pos.y) / distance,
(sink_pos.z - grid_pos.z) / distance};
force_gravity = gravity_magnitude * direction;
return force_gravity;
}
#endif
#if LSINK
Scalar
truelove_density(in Scalar lnrho){
const Scalar rho = exp(value(lnrho));
const Scalar Jeans_length_squared = (M_PI * cs2_sound) / (AC_G_const * rho);
const Scalar TJ_rho = ((M_PI) * ((dsx * dsx) / Jeans_length_squared) * cs2_sound) / (AC_G_const * dsx * dsx);
//TODO: dsx will cancel out, deal with it later for optimization.
Scalar accretion_rho = rho - TJ_rho;
if (accretion_rho < 0){
accretion_rho = Scalar(0);
}
return accretion_rho;
}
Scalar
accretion_profile(int3 globalVertexIdx, in Scalar lnrho){
// QUESTION: do I need to define grid_pos, sink_pos and distance again
// if the sink_gravity kernel will also be called once LSINK swtich is on? Seems redundant.
const Vector grid_pos = (Vector){(globalVertexIdx.x - nx_min) * dsx,
(globalVertexIdx.y - ny_min) * dsy,
(globalVertexIdx.z - nz_min) * dsz};
const Vector sink_pos = (Vector){DCONST_REAL(AC_sink_pos_x),
DCONST_REAL(AC_sink_pos_y),
DCONST_REAL(AC_sink_pos_z)};
const Scalar profile_range = DCONST_REAL(AC_accretion_range);
const Scalar accretion_distance = length(grid_pos - sink_pos);
Scalar accretion_density;
// if ((accretion_distance) <= profile_range){
// // calculate accretion according to chosen criterion for the grid cell.
// accretion_density = truelove_density(lnrho);
// } else {
// accretion_density = Scalar(0.0);
// }
// return accretion_density;
// multiplying the truelove density by a wave function to avoid step-function like accretion profile.
const Scalar weight = exp(-(accretion_distance/profile_range));
const Scalar rate = truelove_density(lnrho);
accretion_density = weight * rate;
return accretion_density;
}
#endif
//TODO: basic structure of this part is as follows
// update_accretion_buffer() <--> accretion_profile() <--> truelove_density()
#if LENTROPY
Vector
momentum(int3 globalVertexIdx, in VectorField uu, in ScalarField lnrho, in ScalarField ss, in VectorField aa) {
const Matrix S = stress_tensor(uu);
const Scalar cs2 = cs2_sound * exp(gamma * value(ss) / cp_sound + (gamma - 1) * (value(lnrho) - lnrho0));
const Vector j = (Scalar(1.) / mu0) * (gradient_of_divergence(aa) - laplace_vec(aa)); // Current density
const Vector B = curl(aa);
//TODO: DOES INTHERMAL VERSTION INCLUDE THE MAGNETIC FIELD?
const Scalar inv_rho = Scalar(1.) / exp(value(lnrho));
// Regex replace CPU constants with get\(AC_([a-zA-Z_0-9]*)\)
// \1
const Vector mom = - mul(gradients(uu), value(uu))
- cs2 * ((Scalar(1.) / cp_sound) * gradient(ss) + gradient(lnrho))
+ inv_rho * cross(j, B)
+ nu_visc * (
laplace_vec(uu)
+ Scalar(1. / 3.) * gradient_of_divergence(uu)
+ Scalar(2.) * mul(S, gradient(lnrho))
)
+ zeta * gradient_of_divergence(uu)
#if LSINK
+ sink_gravity(globalVertexIdx);
#else
;
#endif
return mom;
}
#elif LTEMPERATURE
Vector
momentum(int3 globalVertexIdx, in VectorField uu, in ScalarField lnrho, in ScalarField tt) {
Vector mom;
const Matrix S = stress_tensor(uu);
const Vector pressure_term = (cp_sound - cv_sound) * (gradient(tt) + value(tt) * gradient(lnrho));
mom = -mul(gradients(uu), value(uu)) -
pressure_term +
nu_visc *
(laplace_vec(uu) + Scalar(1. / 3.) * gradient_of_divergence(uu) +
Scalar(2.) * mul(S, gradient(lnrho))) + zeta * gradient_of_divergence(uu)
#if LSINK
+ sink_gravity(globalVertexIdx);
#else
;
#endif
return mom;
}
#else
Vector
momentum(int3 globalVertexIdx, in VectorField uu, in ScalarField lnrho) {
Vector mom;
const Matrix S = stress_tensor(uu);
// Isothermal: we have constant speed of sound
mom = -mul(gradients(uu), value(uu)) -
cs2_sound * gradient(lnrho) +
nu_visc *
(laplace_vec(uu) + Scalar(1. / 3.) * gradient_of_divergence(uu) +
Scalar(2.) * mul(S, gradient(lnrho))) + zeta * gradient_of_divergence(uu)
#if LSINK
+ sink_gravity(globalVertexIdx);
#else
;
#endif
return mom;
}
#endif
Vector
induction(in VectorField uu, in VectorField aa) {
// Note: We do (-nabla^2 A + nabla(nabla dot A)) instead of (nabla x (nabla
// x A)) in order to avoid taking the first derivative twice (did the math,
// yes this actually works. See pg.28 in arXiv:astro-ph/0109497)
// u cross B - ETA * mu0 * (mu0^-1 * [- laplace A + grad div A ])
const Vector B = curl(aa);
const Vector grad_div = gradient_of_divergence(aa);
const Vector lap = laplace_vec(aa);
// Note, mu0 is cancelled out
const Vector ind = cross(value(uu), B) - eta * (grad_div - lap);
return ind;
}
#if LENTROPY
Scalar
lnT( in ScalarField ss, in ScalarField lnrho) {
const Scalar lnT = lnT0 + gamma * value(ss) / cp_sound +
(gamma - Scalar(1.)) * (value(lnrho) - lnrho0);
return lnT;
}
// Nabla dot (K nabla T) / (rho T)
Scalar
heat_conduction( in ScalarField ss, in ScalarField lnrho) {
const Scalar inv_cp_sound = AcReal(1.) / cp_sound;
const Vector grad_ln_chi = - gradient(lnrho);
const Scalar first_term = gamma * inv_cp_sound * laplace(ss) +
(gamma - AcReal(1.)) * laplace(lnrho);
const Vector second_term = gamma * inv_cp_sound * gradient(ss) +
(gamma - AcReal(1.)) * gradient(lnrho);
const Vector third_term = gamma * (inv_cp_sound * gradient(ss) +
gradient(lnrho)) + grad_ln_chi;
const Scalar chi = AC_THERMAL_CONDUCTIVITY / (exp(value(lnrho)) * cp_sound);
return cp_sound * chi * (first_term + dot(second_term, third_term));
}
Scalar
heating(const int i, const int j, const int k) {
return 1;
}
Scalar
entropy(in ScalarField ss, in VectorField uu, in ScalarField lnrho, in VectorField aa) {
const Matrix S = stress_tensor(uu);
const Scalar inv_pT = Scalar(1.) / (exp(value(lnrho)) * exp(lnT(ss, lnrho)));
const Vector j = (Scalar(1.) / mu0) * (gradient_of_divergence(aa) - laplace_vec(aa)); // Current density
const Scalar RHS = H_CONST - C_CONST
+ eta * (mu0) * dot(j, j)
+ Scalar(2.) * exp(value(lnrho)) * nu_visc * contract(S)
+ zeta * exp(value(lnrho)) * divergence(uu) * divergence(uu);
return - dot(value(uu), gradient(ss))
+ inv_pT * RHS
+ heat_conduction(ss, lnrho);
}
#endif
#if LTEMPERATURE
Scalar
heat_transfer(in VectorField uu, in ScalarField lnrho, in ScalarField tt)
{
const Matrix S = stress_tensor(uu);
const Scalar heat_diffusivity_k = 0.0008; //8e-4;
return -dot(value(uu), gradient(tt)) + heat_diffusivity_k * laplace(tt) + heat_diffusivity_k * dot(gradient(lnrho), gradient(tt)) + nu_visc * contract(S) * (Scalar(1.) / cv_sound) - (gamma - 1) * value(tt) * divergence(uu);
}
#endif
#if LFORCING
Vector
simple_vortex_forcing(Vector a, Vector b, Scalar magnitude)
{
return magnitude * cross(normalized(b - a), (Vector){0, 0, 1}); // Vortex
}
Vector
simple_outward_flow_forcing(Vector a, Vector b, Scalar magnitude)
{
return magnitude * (1 / length(b - a)) * normalized(b - a); // Outward flow
}
// The Pencil Code forcing_hel_noshear(), manual Eq. 222, inspired forcing function with adjustable helicity
Vector
helical_forcing(Scalar magnitude, Vector k_force, Vector xx, Vector ff_re, Vector ff_im, Scalar phi)
{
// JP: This looks wrong:
// 1) Should it be dsx * nx instead of dsx * ny?
// 2) Should you also use globalGrid.n instead of the local n?
// MV: You are rigth. Made a quickfix. I did not see the error because multigpu is split
// in z direction not y direction.
// 3) Also final point: can we do this with vectors/quaternions instead?
// Tringonometric functions are much more expensive and inaccurate/
// MV: Good idea. No an immediate priority.
// Fun related article:
// https://randomascii.wordpress.com/2014/10/09/intel-underestimates-error-bounds-by-1-3-quintillion/
xx.x = xx.x*(2.0*M_PI/(dsx*globalGridN.x));
xx.y = xx.y*(2.0*M_PI/(dsy*globalGridN.y));
xx.z = xx.z*(2.0*M_PI/(dsz*globalGridN.z));
Scalar cos_phi = cos(phi);
Scalar sin_phi = sin(phi);
Scalar cos_k_dot_x = cos(dot(k_force, xx));
Scalar sin_k_dot_x = sin(dot(k_force, xx));
// Phase affect only the x-component
//Scalar real_comp = cos_k_dot_x;
//Scalar imag_comp = sin_k_dot_x;
Scalar real_comp_phase = cos_k_dot_x*cos_phi - sin_k_dot_x*sin_phi;
Scalar imag_comp_phase = cos_k_dot_x*sin_phi + sin_k_dot_x*cos_phi;
Vector force = (Vector){ ff_re.x*real_comp_phase - ff_im.x*imag_comp_phase,
ff_re.y*real_comp_phase - ff_im.y*imag_comp_phase,
ff_re.z*real_comp_phase - ff_im.z*imag_comp_phase};
return force;
}
Vector
forcing(int3 globalVertexIdx, Scalar dt)
{
Vector a = Scalar(.5) * (Vector){globalGridN.x * dsx,
globalGridN.y * dsy,
globalGridN.z * dsz}; // source (origin)
Vector xx = (Vector){(globalVertexIdx.x - nx_min) * dsx,
(globalVertexIdx.y - ny_min) * dsy,
(globalVertexIdx.z - nz_min) * dsz}; // sink (current index)
const Scalar cs2 = cs2_sound;
const Scalar cs = sqrt(cs2);
//Placeholders until determined properly
Scalar magnitude = DCONST_REAL(AC_forcing_magnitude);
Scalar phase = DCONST_REAL(AC_forcing_phase);
Vector k_force = (Vector){ DCONST_REAL(AC_k_forcex), DCONST_REAL(AC_k_forcey), DCONST_REAL(AC_k_forcez)};
Vector ff_re = (Vector){DCONST_REAL(AC_ff_hel_rex), DCONST_REAL(AC_ff_hel_rey), DCONST_REAL(AC_ff_hel_rez)};
Vector ff_im = (Vector){DCONST_REAL(AC_ff_hel_imx), DCONST_REAL(AC_ff_hel_imy), DCONST_REAL(AC_ff_hel_imz)};
//Determine that forcing funtion type at this point.
//Vector force = simple_vortex_forcing(a, xx, magnitude);
//Vector force = simple_outward_flow_forcing(a, xx, magnitude);
Vector force = helical_forcing(magnitude, k_force, xx, ff_re,ff_im, phase);
//Scaling N = magnitude*cs*sqrt(k*cs/dt) * dt
const Scalar NN = cs*sqrt(DCONST_REAL(AC_kaver)*cs);
//MV: Like in the Pencil Code. I don't understandf the logic here.
force.x = sqrt(dt)*NN*force.x;
force.y = sqrt(dt)*NN*force.y;
force.z = sqrt(dt)*NN*force.z;
if (is_valid(force)) { return force; }
else { return (Vector){0, 0, 0}; }
}
#endif // LFORCING
// Declare input and output arrays using locations specified in the
// array enum in astaroth.h
in ScalarField lnrho(VTXBUF_LNRHO);
out ScalarField out_lnrho(VTXBUF_LNRHO);
in VectorField uu(VTXBUF_UUX, VTXBUF_UUY, VTXBUF_UUZ);
out VectorField out_uu(VTXBUF_UUX,VTXBUF_UUY,VTXBUF_UUZ);
#if LMAGNETIC
in VectorField aa(VTXBUF_AX,VTXBUF_AY,VTXBUF_AZ);
out VectorField out_aa(VTXBUF_AX,VTXBUF_AY,VTXBUF_AZ);
#endif
#if LENTROPY
in ScalarField ss(VTXBUF_ENTROPY);
out ScalarField out_ss(VTXBUF_ENTROPY);
#endif
#if LTEMPERATURE
in ScalarField tt(VTXBUF_TEMPERATURE);
out ScalarField out_tt(VTXBUF_TEMPERATURE);
#endif
#if LSINK
in Scalar accretion = VTXBUF_ACCRETION;
out Scalar out_accretion = VTXBUF_ACCRETION;
#endif
Kernel void
solve(Scalar dt) {
out_lnrho = rk3(out_lnrho, lnrho, continuity(uu, lnrho), dt);
#if LMAGNETIC
out_aa = rk3(out_aa, aa, induction(uu, aa), dt);
#endif
#if LENTROPY
out_uu = rk3(out_uu, uu, momentum(globalVertexIdx, uu, lnrho, ss, aa), dt);
out_ss = rk3(out_ss, ss, entropy(ss, uu, lnrho, aa), dt);
#elif LTEMPERATURE
out_uu = rk3(out_uu, uu, momentum(globalVertexIdx, uu, lnrho, tt), dt);
out_tt = rk3(out_tt, tt, heat_transfer(uu, lnrho, tt), dt);
#else
out_uu = rk3(out_uu, uu, momentum(globalVertexIdx, uu, lnrho), dt);
#endif
#if LFORCING
if (step_number == 2) {
out_uu = out_uu + forcing(globalVertexIdx, dt);
}
#endif
#if LSINK
// out_lnrho = log(exp(out_lnrho) - accretion_profile(globalVertexIdx, lnrho));
// out_accretion = value(accretion) + (accretion_profile(globalVertexIdx,lnrho) * dsx * dsy * dsz);
out_accretion = rk3(out_accretion, accretion, accretion_profile(globalVertexIdx, lnrho), dt);// unit now is rho!
out_lnrho = log(exp(out_lnrho) - out_accretion);
out_accretion = out_accretion * dsx * dsy * dsz;// unit is now mass!
#endif
}