Rework SolutionLoader

[michaelbynum]

Summary/Motivation:

This PR updates the solution loader in pyomo/contrib/solver based on recent design discussions.

Changes proposed in this PR:

• add get_number_of_solutions method
• add get_solution_ids method
• add load_solution_method
• add load_import_suffixes method
• add solution_id as an argument to methods

Legal Acknowledgement

By contributing to this software project, I have read the contribution guide and agree to the following terms and conditions for my contribution:

1. I agree my contributions are submitted under the BSD license.
2. I represent I am authorized to make the contributions and grant the license. If my employer has rights to intellectual property that includes these contributions, I represent that I have received permission to make contributions and grant the required license on behalf of that employer.

[codecov]

Codecov Report

❌ Patch coverage is 77.40113% with 40 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.12%. Comparing base (749e3ac) to head (0338bcc).
⚠️ Report is 10 commits behind head on main.

Files with missing lines	Patch %	Lines
pyomo/contrib/solver/solvers/asl_sol_reader.py	81.63%	9 Missing ⚠️
pyomo/contrib/solver/solvers/gms_sol_reader.py	62.50%	9 Missing ⚠️
pyomo/contrib/solver/common/solution_loader.py	86.66%	6 Missing ⚠️
...ontrib/solver/solvers/gurobi/gurobi_direct_base.py	64.70%	6 Missing ⚠️
pyomo/contrib/solver/solvers/highs.py	64.28%	5 Missing ⚠️
...contrib/solver/solvers/gurobi/gurobi_persistent.py	71.42%	4 Missing ⚠️
pyomo/contrib/solver/solvers/ipopt.py	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3701      +/-   ##
==========================================
- Coverage   89.47%   88.12%   -1.36%     
==========================================
  Files         908      908              
  Lines      106738   106951     +213     
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- Hits        95509    94253    -1256     
- Misses      11229    12698    +1469     

Flag	Coverage Δ
builders	29.08% <29.37%> (-0.01%)	⬇️
default	85.94% <77.40%> (?)
expensive	35.50% <29.37%> (?)
linux	34.57% <29.37%> (-54.61%)	⬇️
linux_other	34.57% <29.37%> (-52.58%)	⬇️
oldsolvers	27.99% <29.37%> (+0.47%)	⬆️
osx	?
win	?
win_other	?

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[jsiirola]

A couple minor questions that don't need to hold up the PR and one significant one that probably does (it look like the ASL solution loader is not loading all import suffixes).

[jsiirola]

Some questions:

• Should the Suffix be cleared before loading?
• Could this just be:

Suggested change

	for k, v in solution_loader.get_duals(solution_id=solution_id).items():
	dual_suffix[k] = v
	dual_suffix.update(solution_loader.get_duals(solution_id=solution_id))

[michaelbynum]

Done.

[jsiirola]

Instead of Optional[Type], I believe the current "preferred Python" annotation is Type | None. In this case, since Any includes None, I think you could just do Any (although Any | None is a little more explicit).

[michaelbynum]

Done.

[jsiirola]

This only loads duals and rc ... the ASL supports arbitrary inpirt suffixes, which I think need to be supported here.

[michaelbynum]

Can you give me an example of what ASLSolFileData would look like if it had other suffixes. I see that it has attributes like var_suffixes. I assume the keys are the names of the suffixes, and the values map the variable indices to the suffix values? Any suggestions on how to test this?

[jsiirola]

Yes: Suffix data comes back from the ASL flagged for "variables", "constraints", "objectives", and the "problem". We blindly parse that into the corresponding attributes (var_suffixes, etc).

• For var, con, and obj, the dict maps suffix name to a dict that maps the 0-based integer index of the relevant variable / constraint / objective in the corresponding list in the NLWriterInfo returned by the writer tot he suffix value.
• For the problem, since there is only one problem, the problem_suffixes dict just maps suffix name to value.

[michaelbynum]

Done - kind of. I just raise an error if any variables are eliminated or any scaling is done.

[michaelbynum]

@AnhTran01 , @boxblox - could you please take a look at the changes to the gams solution loader?