Draft: Blank functions for MHD support

Changes:

• Moved the signal velocity calculation to a new file that is SPH-scheme independant. There are two versions in there, one for MHD runs, one for non-MHD runs
• Added the mhd directory for the scheme specific things. In there there is only None scheme for now, i.e. no-MHD runs
• Added all the empty functions for the loops over neighbours
• Added all the empty functions for the things done in-between loops (drift, kick, reset...)
• Added a small structure that is carried by the particles to contain the MHD fields.

Todo:

• Deal with the case where the MHD wants three loops but the hydro only needs two...
• Deal with Gasoline signal velocity
• Prevent MHD + Gizmo
• Unit tests
• Cleanly deal with mu_0
• Cleanly deal with stats
• Cleanly deal with div v
• Work out units of B^2 PS.
• Deal with 0 ngbs in FDI and VP.

added SPH enhancement labels

@fastasyszyn @okarapiperis @bvandenbroucke we can list technical issues here.

I'd recommend creating a branch off of this branch to add your own schemes. And then merge regularly this branch into yours.

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• a667b04f - Added missing MHD io file
• 725fb55a - Added the particle-carried MHD structure to the other relevant hydro schemes

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• af5ba8f2 - Added the particle-carried MHD structure to the other relevant hydro schemes

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To add your own scheme, copy the None directory in src/mhd, edit src/Makefile.am, src/mhd.h, src/mhd_io.h, src/mhd_struct.h, and configure.ac.

Then add anything you like to the functions in src/mhd/YourScheme

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• e0142279 - Added an empty direct-induction MHD set of functions.
• da217f0a - Added missing function definitions in the 'None' MHD scheme.

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@okarapiperis I have now added a "direct induction" flavour of MHD.

To compile, do:

./configure --with-mhd=direct-induction

All the files needing to edit are in src/mhd/DirectInduction.

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• 4715f3b7 - First Commit of MHD tests

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• 1f72eb7b - blid vesion of mhd flavors: Base Direct Indution and Vector Potentials

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added 3 commits

• 72565a7b - Missing call to MHD function in the naive PAIR1
• 0c44f847 - Add the new mhd calls to the symmetry test
• aef0d89b - Add empty debugging function printing out the particle fields to the 'none'...

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added 3 commits

• 594b39fd - Rename the configuration option --with-mhd to --with-spmhd
• cb3a1ac1 - Better name for the two SPMHD schemes managed by @fastasyszyn
• 19e40b90 - Prevent users from running a gizmo hydro scheme alongside an SPMHD scheme

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marked the checklist item Prevent MHD + Gizmo as completed

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• bb245239 - Add blank-for-now debugging SPMHD functions

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• 6cd407db - Add the distance vector as an argument to the signal velocity calculation function

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added 15 commits

• b4d1e9fd - first commit of the branch, and rought idea of MU0
• 104106ad - IO & particle definitions
• 2fc64c9c - Bug fix Returned fields form IO functions
• 6df0db48 - Non working version of Direct Induction
• 200420c0 - Missing call to MHD function in the naive PAIR1
• aab35f9a - Add the new mhd calls to the symmetry test
• 2f065e57 - Add empty debugging function printing out the particle fields to the 'none'...
• e15ac7f0 - Add debugging function to the other two MHD schemes
• 676bf69a - Merge branch 'MHD_canvas' into 'MHD_FS'
• 392394e2 - Formatting
• 4609f46d - DX into signal velocity && clang-format-10
• 2a791563 - format
• 912242a8 - Formatted and debugged version
• fa3cbbf7 - DI working version
• f01c5499 - Merge branch 'MHD_FS' into 'MHD_canvas'

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• 73660a80 - Naming problem

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• 34ba467e - Adapt unit tests to the new SPMHD loops

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marked the checklist item Unit tests as completed