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DTSTART;TZID=Europe/Stockholm:20240604T094100
DTEND;TZID=Europe/Stockholm:20240604T094200
UID:submissions.pasc-conference.org_PASC24_sess158_pos138@linklings.com
SUMMARY:P22 - FFT-Accelerated Polynomial Transforms for Fully Spectral Sim
 ulations
DESCRIPTION:Poster\n\nDmitrii Tolmachev, Philippe Marti, and Giacomo Casti
 glioni (ETH Zurich); Daniel Ganellari (ETH Zurich / CSCS); and Andrew Jack
 son (ETH Zurich)\n\nOne of the most time-consuming parts of our CFD framew
 ork QuICC is the computation of the physical to spectral space transformat
 ions. In spherical geometry, this transformation can be decomposed into th
 ree main parts: Fourier Transform and Spherical Harmonics Transform for an
 gular parts and Jones-Worland Transform for the radial part. In this poste
 r, we present a modern polynomial order connection approach for these calc
 ulations. It reformulates the complex polynomial transforms as FFTs throug
 h a sequence of order manipulations using well-established polynomial recu
 rrence relations and Discrete Cosine Transforms (DCT), which in turn are c
 alculated with the help of the VkFFT library. The recurrence relations are
  calculated as a sequence of bidiagonal matrix multiplications and backsol
 ves implemented as a separate library called PfSolve. We also present the 
 benchmark evaluation of the implemented algorithm against the common quadr
 ature approach and evaluate the memory and accuracy gains. This benchmark 
 is performed with the help of the testing suite of QuICC and will consider
  modern HPC solutions from both AMD and Nvidia due to the cross-platform s
 upport of the runtime code generation platform used for both PfSolve and V
 kFFT.\n\nSession Chair: Iva Kavcic (Met Office)
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