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15 years of Pencil code: History and latest developments

15 years of Pencil code: History and latest developments. Public  Scientic usage Variety, developers Teaching examples. Pencil Code Philosophy. Maximum freedom Alternatives possible Research-driven Can’t expect service Minimum ties Acknowledge development work of others

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15 years of Pencil code: History and latest developments

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  1. 15 years of Pencil code: History and latest developments Public  Scientic usage Variety, developers Teaching examples

  2. Pencil Code Philosophy • Maximum freedom • Alternatives possible • Research-driven • Can’t expect service • Minimum ties • Acknowledge development work of others • Only one version • Minimal duplication

  3. Credit

  4. Free licence, but giving credit to research

  5. Using ADSlab; search for “Pencil Code”

  6. Picked up by community

  7. Assemble bibtex file

  8. Variety of usage • Interstellar medium • Galaxy clusters, Early Universe • Planet formation • Inertial particles, raindrop formation • Accretion disks • Shear flows • Solar Physics • Coronal heating, dynamos, spot formation • Convection, global convective dynamos • Miscellanea • Test-field method, Hydro turb, turb combustion

  9. Assemble bibtex file

  10. Assemble bibtex file

  11. Usage of “Pencil” rather common…

  12. Usage of “Pencil” rather common…

  13. Pencil formulation • In CRAY days: worked with full chunks f(nx,ny,nz,nvar) • Now, on SGI, nearly 100% cache misses • Instead work with f(nx,nvar), i.e. one nx-pencil • No cache misses, negligible work space, just 2N • Can keep all components of derivative tensors • Communication before sub-timestep • Then evaluate all derivatives, e.g. call curl(f,iA,B) • Vector potential A=f(:,:,:,iAx:iAz), B=B(nx,3)

  14. Switch modules • magnetic or nomagnetic (e.g. just hydro) • hydro or nohydro (e.g. kinematic dynamo) • density or nodensity (burgulence) • entropy or noentropy (e.g. isothermal) • radiation or noradiation (solar convection, discs) • dustvelocity or nodustvelocity (planetesimals) • Coagulation, reaction equations • Chemistry (reaction-diffusion-advection equations) Other physics modules: MHD, radiation, partial ionization, chemical reactions, selfgravity

  15. High-order schemes • Alternative to spectral or compact schemes • Efficiently parallelized, no transpose necessary • No restriction on boundary conditions • Curvilinear coordinates possible (except for singularities) • 6th (or other) order central differences in space • Non-conservative scheme • Allows use of logarithmic density and entropy • Copes well with strong stratification and temperature contrasts

  16. (i) High-order spatial schemes Main advantage: low phase errors Near boundaries: x x x x x x x x x ghost zones interior points

  17. Wavenumber characteristics

  18. Higher order – less viscosity

  19. (ii) High-order temporal schemes Main advantage: low amplitude errors 2N-RK3 scheme (Williamson 1980) 2nd order 3rd order 1st order

  20. Intrinsic Calculation Ray direction Transfer equation & parallelization Processors Analytic Solution:

  21. Analytic Solution: Communication Ray direction The Transfer Equation & Parallelization Processors

  22. Analytic Solution: Intrinsic Calculation Ray direction The Transfer Equation & Parallelization Processors

  23. Realistic Solar MHD

  24. Use temperature

  25. Useful units, etc

  26. Basic equations

  27. Working with temperature Y=0.24: mass fract xHe=0.08: vol fract

  28. Pressure gradient

  29. Saha equation Opacity: either Kramers or Hminus

  30. With/without ionization

  31. Move to Github

  32. Graphs1

  33. Graphs1

  34. H-index of check-ins

  35. Automatic validation tests

  36. Scaling

  37. For this afteroon

  38. Roadmap The Yin-Yang mesh

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