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Rigid injection: Center field scaling around the v push (#5389)
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In the rigid injection, the fields where scale by the fraction of time
spent between `n*dt` and `(n+1)*dt` to the right of the injection plane.
However, to be consistent with the leap-frog velocity update, this needs
to be between `(n-1/2)*dt` and `(n+1/2)*dt` instead.

As a side-effect of this PR, saving and re-setting `u` and
`optical_depth` to their original value is not needed anymore since the
scaling factor for E and B is 0 for particles to the left of the plane.
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@RemiLehe
RemiLehe authored Nov 1, 2024
1 parent 057d403 commit 20a7954
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Showing 6 changed files with 106 additions and 137 deletions.
18 changes: 9 additions & 9 deletions Regression/Checksum/benchmarks_json/test_1d_fel.json
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@@ -1,31 +1,31 @@
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56 changes: 28 additions & 28 deletions Regression/Checksum/benchmarks_json/test_2d_comoving_psatd_hybrid.json
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@@ -1,38 +1,38 @@
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56 changes: 28 additions & 28 deletions Regression/Checksum/benchmarks_json/test_2d_galilean_psatd_hybrid.json
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@@ -1,38 +1,38 @@
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52 changes: 26 additions & 26 deletions Regression/Checksum/benchmarks_json/test_2d_laser_acceleration_boosted.json
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@@ -1,38 +1,38 @@
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17 changes: 15 additions & 2 deletions Source/Particles/Gather/ScaleFields.H
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Original file line number Diff line number Diff line change
Expand Up @@ -47,8 +47,21 @@ struct ScaleFields
// This only approximates what should be happening. The particles
// should by advanced a fraction of a time step instead.
// Scaling the fields is much easier and may be good enough.
const amrex::Real dtscale = 1._rt - (m_z_plane_previous - zp)/(m_vz_ave_boosted + m_v_boost)/m_dt;
if (0._rt < dtscale && dtscale < 1._rt)

// The scaling factor corresponds to the fraction of time that
// the particles spends to the right of the injection plane,
// between (n-1/2)*dt and (n+1/2)*dt, which is the interval
// over which the velocity is updated, in the leap-frog velocity push.
// (Note that here, `zp` is the particle position at time n*dt)
amrex::Real dtscale = 0.5_rt - (m_z_plane_previous - zp)/(m_vz_ave_boosted + m_v_boost)/m_dt;
// If the particle stays to the left of the plane during the
// whole push, simply set the scaling factor to 0, and thus
// the velocity push leaves the velocity unchanged.
if (dtscale < 0._rt) {
dtscale = 0;
}
// Scale the fields.
if (dtscale < 1._rt)
{
Exp *= dtscale;
Eyp *= dtscale;
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44 changes: 0 additions & 44 deletions Source/Particles/RigidInjectedParticleContainer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -176,10 +176,6 @@ RigidInjectedParticleContainer::PushPX (WarpXParIter& pti,

// Save the position, momentum and optical depth, making copies
amrex::Gpu::DeviceVector<ParticleReal> xp_save, yp_save, zp_save;
amrex::Gpu::DeviceVector<ParticleReal> uxp_save, uyp_save, uzp_save;
#ifdef WARPX_QED
amrex::Gpu::DeviceVector<ParticleReal> optical_depth_save;
#endif

const auto GetPosition = GetParticlePosition<PIdx>(pti, offset);
auto SetPosition = SetParticlePosition<PIdx>(pti, offset);
Expand All @@ -188,54 +184,24 @@ RigidInjectedParticleContainer::PushPX (WarpXParIter& pti,
amrex::ParticleReal* const AMREX_RESTRICT uy = uyp.dataPtr() + offset;
amrex::ParticleReal* const AMREX_RESTRICT uz = uzp.dataPtr() + offset;

#ifdef WARPX_QED
const bool loc_has_quantum_sync = has_quantum_sync();
amrex::ParticleReal* AMREX_RESTRICT p_optical_depth = nullptr;
amrex::ParticleReal* AMREX_RESTRICT p_optical_depth_save = nullptr;
#endif

if (!done_injecting_lev)
{
// If the old values are not already saved, create copies here.
xp_save.resize(np_to_push);
yp_save.resize(np_to_push);
zp_save.resize(np_to_push);

uxp_save.resize(np_to_push);
uyp_save.resize(np_to_push);
uzp_save.resize(np_to_push);

amrex::ParticleReal* const AMREX_RESTRICT xp_save_ptr = xp_save.dataPtr();
amrex::ParticleReal* const AMREX_RESTRICT yp_save_ptr = yp_save.dataPtr();
amrex::ParticleReal* const AMREX_RESTRICT zp_save_ptr = zp_save.dataPtr();

amrex::ParticleReal* const AMREX_RESTRICT uxp_save_ptr = uxp_save.dataPtr();
amrex::ParticleReal* const AMREX_RESTRICT uyp_save_ptr = uyp_save.dataPtr();
amrex::ParticleReal* const AMREX_RESTRICT uzp_save_ptr = uzp_save.dataPtr();

#ifdef WARPX_QED
if(loc_has_quantum_sync){
p_optical_depth = pti.GetAttribs(particle_comps["opticalDepthQSR"]).dataPtr()
+ offset;
optical_depth_save.resize(np_to_push);
p_optical_depth_save = optical_depth_save.dataPtr();
}
#endif

amrex::ParallelFor( np_to_push,
[=] AMREX_GPU_DEVICE (long i) {
amrex::ParticleReal xp, yp, zp;
GetPosition(i, xp, yp, zp);
xp_save_ptr[i] = xp;
yp_save_ptr[i] = yp;
zp_save_ptr[i] = zp;
uxp_save_ptr[i] = ux[i];
uyp_save_ptr[i] = uy[i];
uzp_save_ptr[i] = uz[i];
#ifdef WARPX_QED
if(loc_has_quantum_sync){
p_optical_depth_save[i] = p_optical_depth[i];}
#endif
});
}

Expand All @@ -252,9 +218,6 @@ RigidInjectedParticleContainer::PushPX (WarpXParIter& pti,
amrex::ParticleReal* AMREX_RESTRICT x_save = xp_save.dataPtr();
amrex::ParticleReal* AMREX_RESTRICT y_save = yp_save.dataPtr();
amrex::ParticleReal* AMREX_RESTRICT z_save = zp_save.dataPtr();
amrex::ParticleReal* AMREX_RESTRICT ux_save = uxp_save.dataPtr();
amrex::ParticleReal* AMREX_RESTRICT uy_save = uyp_save.dataPtr();
amrex::ParticleReal* AMREX_RESTRICT uz_save = uzp_save.dataPtr();

// Undo the push for particles not injected yet.
// The zp are advanced a fixed amount.
Expand All @@ -267,9 +230,6 @@ RigidInjectedParticleContainer::PushPX (WarpXParIter& pti,
amrex::ParticleReal xp, yp, zp;
GetPosition(i, xp, yp, zp);
if (zp <= z_plane_lev) {
ux[i] = ux_save[i];
uy[i] = uy_save[i];
uz[i] = uz_save[i];
xp = x_save[i];
yp = y_save[i];
if (rigid) {
Expand All @@ -281,10 +241,6 @@ RigidInjectedParticleContainer::PushPX (WarpXParIter& pti,
zp = z_save[i] + dt*uz[i]*gi;
}
SetPosition(i, xp, yp, zp);
#ifdef WARPX_QED
if(loc_has_quantum_sync){
p_optical_depth[i] = p_optical_depth_save[i];}
#endif
}
});
}
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