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DTSTAMP:20260522T162631Z
LOCATION:Bldg. 6 - Room 002
DTSTART;TZID=Europe/Stockholm:20260701T113000
DTEND;TZID=Europe/Stockholm:20260701T120000
UID:submissions.pasc-conference.org_PASC26_sess172_pap109@linklings.com
SUMMARY:A High-Performance Elliptic Solver for Plasma Boundary Turbulence 
 Codes
DESCRIPTION:Andreas Stegmeir (Max Planck Institute for Plasma Physics), Cr
 istian Lalescu and Mou Lin (Max Planck Computing and Data Facility), Jordy
  Trilaksono (Max Planck Institute for Plasma Physics), Nicola Varini (EPFL
 ), and Tilman Dannert (Max Planck Computing and Data Facility)\n\nElliptic
  equations play a crucial role in turbulence models for magnetic confineme
 nt fusion. Regardless of the chosen modeling approach - whether gyrokineti
 c, gyrofluid, or drift-fluid - the Poisson equation and Ampere's law lead 
 to elliptic problems that must be solved on 2D planes perpendicular to the
  magnetic field. In this work, we present an efficient solver for such gen
 eralised elliptic problems, especially suited for the conditions in the bo
 undary region. A finite difference discretisation is employed, and the sol
 ver is based on a flexible generalised minimal residual method (fGMRES) wi
 th a geometric multigrid preconditioner. We present implementations with O
 penMP parallelisation and GPU acceleration, with backends in CUDA and HIP.
  On the node level, significant speed-ups are achieved with the GPU implem
 entation, exceeding external library solutions such as rocALUTION. In acco
 rdance with theoretical scaling laws for multigrid methods, we observe lin
 ear scaling of the solver with problem size, O(N). This solver is implemen
 ted in the PARALLAX/PAccX libraries and serves as a central component of t
 he plasma boundary turbulence codes GRILLIX and GENE-X\n\nSession Chair: A
 ndreas Adelmann (Paul Scherrer Institute, ETH Zurich)\n\n
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