Sts cleanup

[danieljprice]

Description:
Super-timestepping functionality [implemented for non-ideal MHD] is obsolete (c.f. Biriukov thesis work). We also now have the ability to implement implicit resistivity as done in sphNG via the resistivity_implicit module, so there is no longer a need for super-timestepping to alleviate the non-ideal MHD tilmestep constraint.

Components modified:

• Setup (src/setup)
• Main code (src/main)
• Moddump utilities (src/utils/moddump)
• Analysis utilities (src/utils/analysis)
• Documentation (docs/)

Type of change:

• Bug fix
• Physics improvements
• Better initial conditions
• Performance improvements
• Documentation update
• Other (please describe)
  cleanup of obsolete functionality

Testing:

Code compiles and tests run in absence of sts functionality

Did you run the bots? yes

Did you update relevant documentation in the docs directory? n/a

Did you add comments such that the purpose of the code is understandable? yes

Is there a unit test that could be added for this feature/bug? no

If so, please describe what a unit test might check:
n/a

Related issues: #55

[gemini-code-assist]

Summary of Changes

Hello @danieljprice, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request focuses on a significant cleanup of the codebase by completely removing the Super-Timestepping (STS) functionality. This feature, previously employed for non-ideal MHD simulations, is now obsolete due to advancements in implicit resistivity implementation. The changes span across various core and utility modules, eliminating STS-specific code, compiler directives, and associated logic, thereby simplifying the simulation's time-stepping mechanisms and overall architecture.

Highlights

• Removal of Super-Timestepping (STS) Functionality: The core Super-Timestepping (STS) functionality, previously used for non-ideal MHD, has been entirely removed as it is now considered obsolete. This includes the deletion of dedicated STS modules and associated logic.
• Obsolete Feature Justification: The removal is justified by recent thesis work (Biriukov) and the new capability to implement implicit resistivity via the resistivity_implicit module, which negates the need for STS to alleviate non-ideal MHD timestep constraints.
• Codebase Cleanup: Numerous files across the build, src/main, src/setup, and src/tests directories have been updated to remove references, compiler flags, variables, and logic related to STS, streamlining the codebase.
• Type Conversion Refinements: Several analysis utility files (analysis_BRhoOrientation.F90, analysis_NSmerger.f90, analysis_bzrms.f90, analysis_common_envelope.f90, analysis_mapping_mass.f90, analysis_polytropes.f90, analysis_protostar_environ.F90, analysis_sphere.f90) have been updated to use real() for type conversions instead of float(), improving consistency and precision.

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[gemini-code-assist]

Code Review

This pull request provides a significant cleanup by removing the obsolete super-timestepping (STS) functionality. The changes are extensive, touching many files from the build system to core physics routines, and appear to be consistent and well-executed. This simplification of the codebase is a valuable improvement.

I've also noticed that in several analysis files, the obsolete float() intrinsic has been replaced with real(). This is a great modernization. I've added a couple of comments with suggestions to make this pattern even more robust by explicitly specifying the kind in the real() conversion, which improves type safety and maintainability.

Overall, this is a solid cleanup effort.

[gemini-code-assist]

It's good that you're replacing the obsolete float() intrinsic with real(). For better type safety and clarity, it's recommended to specify the kind of the real number. Since xsend is declared as real(kind=8), you could use real(id, kind=8) or, more robustly, real(id, kind=kind(xsend)). This ensures that the conversion is always to the correct precision, even if the kind of xsend changes in the future.

 xsend(2) = real(id, kind=kind(xsend))

[gemini-code-assist]

It's good practice to replace the obsolete float() intrinsic with real(). I've noticed this has been done in several analysis files. To further improve type safety and code clarity, I recommend specifying the kind for the conversion. For example, real(nbins, kind=kind(drho)). This ensures the integer is converted to the correct precision, matching the variable it's used with, and makes the code more robust against changes in floating-point precision settings. This applies to all similar conversions in this block and other files (e.g., analysis_NSmerger.f90, analysis_sphere.f90, etc.).

 drho  = (log10(rhomax) - log10(rhomin))/real(nbins, kind=kind(drho))
 dB    = (log10(Bmax)   - log10(Bmin))/real(nbins, kind=kind(dB))
 dv    = (log10(vmax)   - log10(vmin))/real(nbins, kind=kind(dv))
 dcost = (costmax - costmin)/real(nbins, kind=kind(dcost))
 dvt   = (vtmax   - vtmin  )/real(nbins, kind=kind(dvt))

[gemini-code-assist]

Good job replacing float() with real(). To make this more robust, you can specify the kind for the type conversion, e.g., real(bincountmaj(i), kind=kind(avvinbinmaj)). This ensures type consistency and avoids potential precision issues. This applies to all similar conversions in this block.

       avvinbinmaj(i) = vinbinmaj(i)  /real(bincountmaj(i), kind=kind(avvinbinmaj))
       alphabinmaj(i) = alphabinmaj(i)/real(bincountmaj(i), kind=kind(alphabinmaj))
       partdensmaj(i) = real(bincountmaj(i), kind=kind(partdensmaj))*particlemass/vol(i)
    endif
    if (bincountmin(i) > 0) then
       avvinbinmin(i) = vinbinmin(i)  /real(bincountmin(i), kind=kind(avvinbinmin))
       alphabinmin(i) = alphabinmin(i)/real(bincountmin(i), kind=kind(alphabinmin))
       partdensmin(i) = real(bincountmin(i), kind=kind(partdensmin))*particlemass/vol(i)
       print*, partdensmin(i) ,real(bincountmin(i), kind=kind(partdensmin)),particlemass,vol(i)
    endif
    if (bincountavg(i) > 0) then
       avvinbinavg(i) = vinbinavg(i)  /real(bincountavg(i), kind=kind(avvinbinavg))
       alphabinavg(i) = alphabinavg(i)/real(bincountavg(i), kind=kind(alphabinavg))
       partdensavg(i) = real(bincountavg(i), kind=kind(partdensavg))*particlemass/(vol(i)*pi/dtheta)