2025-09-01

- 1 General things to do
  - 1.1 Tests
  - 1.2 Optimizations
  - 1.3 Wasora keywords
  - 1.4 Wasora-like stuff
  - 1.5 API
  - 1.6 Nice to have
  - 1.7 Command-line arguments
  - 1.8 Error handling
  - 1.9 Postprocessing output
- 2 Meshes
- 3 PDEs
  - 3.1 Laplace/Poisson/Helmholtz
  - 3.2 Heat
  - 3.3 Mechanical
  - 3.4 Modal
  - 3.5 Neutron
- 4 V & V
- 5 PDEs

  [1 General things to do]: #general-things-to-do
  [1.1 Tests]: #tests
  [1.2 Optimizations]: #optimizations
  [1.3 Wasora keywords]: #wasora-keywords
  [1.4 Wasora-like stuff]: #wasora-like-stuff
  [1.5 API]: #api
  [1.6 Nice to have]: #nice-to-have
  [1.7 Command-line arguments]: #command-line-arguments
  [1.8 Error handling]: #error-handling
  [1.9 Postprocessing output]: #postprocessing-output
  [2 Meshes]: #meshes
  [3 PDEs]: #pdes
  [3.1 Laplace/Poisson/Helmholtz]: #laplacepoissonhelmholtz
  [3.2 Heat]: #heat
  [3.3 Mechanical]: #mechanical
  [3.4 Modal]: #modal
  [3.5 Neutron]: #neutron
  [4 V & V]: #v-v
  [5 PDEs]: #pdes-1

General things to do

- windows build (against my will)
- PROGRESS ascii_art percentage norm
  - build, KSP, SNES
- implicit call to SOLVE_PROBLEM?
- for/while loops?
- use DMPlex?
  - to read non-gmsh meshes?
  - to partition meshes on the fly?
  - allocate matrices?
  - dump states?
  - choose to use it or not
- FIT to mesh-based functions
- FIT taking into account uncertainties
- extended integration (as in reduced, full, extended)
- make GSL optional
  - rewrite BLAS using ad-hoc routines
    - profile GSL BLAS vs. manual implementation vs. OpenBLAS
    - eigen in C++ (optional)
  - define fee_matrix as gsl_matrix but allow to change the
    implementation
  - wrap all GSL calls inside #ifdef
  - use a large chunk of contiguous memory in the heap to store shape
    functions, gradients, etc
- optimize MPI usage
  - variables mpi_rank, mpi_size, memory_total y memory_local(rank)
- V&V
  - fully document tests
  - section for MMS

Tests

- use the same documentation strategy from doc/examples in tests
- write a README and an explanation of each test
- cell-based mesh writes and integrations
- FIT ranges
- more MPI tests

Optimizations

- if the elements are straight all the jacobians are the same and there
  is no need to sweep over gauss points
- make two lists of elements, one for bulk and one for BCs and loop over
  those
- re-think fem.c to store per-gauss point data in a cache-friendly way
- remove branches (and replace with what?)
- use ad-hoc matrices instead of gsl_matrix?
  - have a contiguous array of memory that stores all the per-element
    matrices in a row-major order
  - access them using macros dhdx(row,col)
  - mind SSE!
  - https://github.com/niswegmann/small-matrix-inverse
- have compile-time macros that will optimize for
  - speed
  - memory
  - something else
- create FeenoX flavors with compile-time
  - problem type (so we can avoid function pointers)
  - problem dimension (so we can hardcode sizes)
  - full or axi-symmetry
  - scalar size (float or double)
  - all elements are of the same type
- use MatSetValuesBlocked()

Wasora keywords

- SEMAPHORE + SHARED_MEMORY
- READ / WRITE
- M4 (MUSTACHE? MACRO?)
- SHELL
- HISTORY
- PRINT_FUNCTION PHYSICAL_ENTITY -> for dumping and reading back BCs
- CALL user routines (check hash of feenox.h)

Wasora-like stuff

- vector & matrix assignments & DAEs
- debug mode, line-by-line
  - run feenox with an option like -d or --debug and then present a
    gdb-like interface with print, and step by step advances
- trap and handle signit & sigterm

API

- Python?
- Julia?
- come up with an example in C

Nice to have

- ask how to set OMP_NUM_THREADS=1
- logarithmic ranges for PRINT_FUNCTION
- default separator after TEXT should be space, after numerical should
  be tab
- PRINT_FUNCTION with %f in between arguments (like PRINT_VECTOR)
- BLAS
  - BLAS a * b = s   # scalar dot
  - BLAS a x b = c   # vector cross
  - BLAS A * b = c   # matrix-vector
  - BLAS a + b = c   # vector
  - BLAS A + B = C   # matrix
  - BLAS a - b = c
  - BLAS A - B = C

Command-line arguments

- list symbols with -l

Error handling

- GSL error handling
- feenox_nan_error()
- feenox_gsl_handler()

Postprocessing output

- formats
  - xdmf? (needs DMView() and VecView())
  - frd? (to be able to use ccx’s post processor… is it worth it?)
  - binary msh and vtu
  - msh v4.1
  - cgns?
  - med?
- full tensors

Meshes

- expose the vectors with the node coordinates

PDEs

- check when the matrices do not need to be rebuilt – use constant flag
- remove the need of needing an explicit SOLVE_PROBLEM
  - detect which variables/functions are PDE outputs and call
    solve_problem() the first time they are needed
- benchmark MPI (read .msh with partitioning info first)
- glue (mortar)
- investigate -mpi_linear_solver_server
- direct elimination for multi-freedom BCs
- third-medium contact?

Laplace/Poisson/Helmholtz

- poisson f = 1, eta = 0
- helmholtz f = 1, eta = 1
- investigate dsyrk() instead of dgemmv()
  https://stackoverflow.com/questions/47013581/blas-matrix-by-matrix-transpose-multiply

Heat

- improve parallel runs
- convection with a separate matrix? think!
- explain that radiation is better off as an expression
- same for total heat sources/bcs
- orthotropic conductivity

Mechanical

- be able to use λ & μ, K & μ, etc.
- strain energy for non-linear
- reactions for non-linear
- many volumes
  - same models
  - different models
- compare with other solvers
  - mofem
  - fenicsx
  - ccx
  - code aster
- check det (F) ≠ 0
- examples
- plasticity
- stresses: count negative jacobians and worst jacobians
- strain energy density
- quasi-static: use PETSc’s TS
  - if a simple SNES does not converge, convert to TS
  - if det F ≤ 0, convert to TS
  - PROBLEM AUTO_LOAD_STEPS

Modal

- partially-unconstrained DOFs in arbitrary directions

Neutron

- current in BCs
- FVM?
- allow per-material fission spectrum (it has to be uniform and
  normalized)

V & V

- MMS

PDEs

- CFD?
- LBM?
- Electromagnetism?
- FVM