1 files changed, 30 insertions, 0 deletions
diff --git a/Source/Particles/Pusher/UpdatePosition.H b/Source/Particles/Pusher/UpdatePosition.H
new file mode 100644
index 000000000..0a4f579f4
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+++ b/Source/Particles/Pusher/UpdatePosition.H
@@ -0,0 +1,30 @@
+#ifndef WARPX_PARTICLES_PUSHER_UPDATEPOSITION_H_
+#define WARPX_PARTICLES_PUSHER_UPDATEPOSITION_H_
+
+#include <AMReX_FArrayBox.H>
+#include <WarpXConst.H>
+#include <AMReX_REAL.H>
+
+/* \brief Push the particle's positions over one timestep,
+ *    given the value of its momenta `ux`, `uy`, `uz` */
+AMREX_GPU_HOST_DEVICE AMREX_INLINE
+void UpdatePosition(
+    amrex::Real& x, amrex::Real& y, amrex::Real& z,
+    const amrex::Real ux, const amrex::Real uy, const amrex::Real uz,
+    const amrex::Real dt )
+{
+
+    constexpr amrex::Real inv_c2 = 1./(PhysConst::c*PhysConst::c);
+
+    // Compute inverse Lorentz factor
+    const amrex::Real inv_gamma = 1./std::sqrt(1. + (ux*ux + uy*uy + uz*uz)*inv_c2);
+    // Update positions over one time step
+    x += ux * inv_gamma * dt;
+#if (AMREX_SPACEDIM == 3) || (defined WARPX_RZ) // RZ pushes particles in 3D
+    y += uy * inv_gamma * dt;
+#endif
+    z += uz * inv_gamma * dt;
+
+}
+
+#endif // WARPX_PARTICLES_PUSHER_UPDATEPOSITION_H_