Diskless/stateless MOPAC API

[godotalgorithm]

This is an open PR for a new MOPAC API that is diskless and stateless. It exposes a limited set of core features: SCF calculations, geometry relaxation, and vibrational frequencies. Also, it gives access to the fast MOZYME solver for SCF calculations and geometry relaxation. Most inputs and outputs are collected and passed through Fortran types provided by the API, and the entire state of the calculation is described by that information. This API also completely avoids using the disk for input and output, which maybe be useful for high-throughput calculations on large, parallel computers with slow disks.

The intent of this API is to supersede #96, which was used as a starting point for the design of this API. All the features of that API are available in some form through this API.

The main features of the API are all implemented, but testing has just started. This open PR includes a simple unit testing system for the API, but there is only one test implemented so far and the testing criteria need to be expanded and refined to cover all the features and relevant data of the API. I expect bugs will be identified and fixed in the process of expanding the testing coverage of the API, and the PR won't be merged until all features are thoroughly tested by these unit tests.

Status

• Ready for merge

[codecov]

Codecov Report

Attention: Patch coverage is 79.52899% with 339 lines in your changes missing coverage. Please review.

Project coverage is 67.22%. Comparing base (a22996f) to head (d6f24c8).
Report is 51 commits behind head on main.

Files with missing lines	Patch %	Lines
src/MOZYME/iter_for_MOZYME.F90	10.00%	126 Missing ⚠️
src/interface/mopac_api_saveload.F90	50.42%	59 Missing ⚠️
tests/mopac_api_test.F90	94.38%	40 Missing ⚠️
src/interface/mopac_api_operations.F90	65.38%	36 Missing ⚠️
src/models/switch.F90	82.87%	31 Missing ⚠️
src/interface/mopac_api_initialize.F90	87.66%	19 Missing ⚠️
src/utilities/seconds.F90	50.00%	7 Missing ⚠️
src/interface/mopac_api_finalize.F90	95.80%	6 Missing ⚠️
src/optimization/ef.F90	63.63%	4 Missing ⚠️
src/optimization/flepo.F90	25.00%	3 Missing ⚠️
... and 5 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #203      +/-   ##
==========================================
+ Coverage   66.75%   67.22%   +0.47%     
==========================================
  Files         332      336       +4     
  Lines       74082    75424    +1342     
==========================================
+ Hits        49456    50707    +1251     
- Misses      24626    24717      +91     

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[thegodone]

This is a impressive stepm thanks for you effort. I guess when it will be ready we can move to python interaction more easily.

[godotalgorithm]

The API is now passing a minimal set of tests for all of the basic functionality. I still need to test some periodic systems and cases with COSMO enabled, and I need to perform more error handling, especially for malformed inputs. FORCETS does not presently support periodic systems, and this support needs to be added for the API to function correctly for vibrational calculations of periodic systems. Overall, the API is in good enough shape now to add to the development version, although it still needs more testing and work before the next production release.