Separate `solver_available` and `license_available` by mrmundt · Pull Request #3730 · Pyomo/pyomo

mrmundt · 2025-09-16T20:34:07Z

Fixes None (but is part of #3688)

Summary/Motivation:

As part of the solver redesign, we decided to separate the checks for solver_available (is the solver findable, e.g., through importing, on the path, etc.) and license_is_valid (does the user have a valid license to use the solver).

This PR introduces a fundamental change in which each derived class is now expected to create both solver_available and license_available. The combination of these two results is then propagated to available (which overall returns a bool stating whether a solver is both findable and licensed).

Changes proposed in this PR:

Create pyomo.contrib.solver.common.availability for SolverAvailability and LicenseAvailability enums
Add license_available and solver_available to SolverBase
Update all existing solvers to implement license_available and solver_available (and properly do caching for version and availability)
- @michaelbynum - I'd love your eyes on the changes in gurobi in particular; they work but you might want it implemented differently
Remove config as an argument in IPOPT
Update / add tests

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:

I agree my contributions are submitted under the BSD license.
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.

michaelbynum · 2025-09-16T21:44:14Z

+            )
+        return self._version_cache
+
+    def license_available(


Should we separate acquire_license and license_available?

Probably. What is the right way to acquire a license in gurobi? Could you help with that?

For anyone following along, we are discussing this offline.

…direct tests

michaelbynum

Overall, I think this looks good. I am happy with the design. I have a few questions/suggestions on the details/implementation.

michaelbynum · 2025-09-17T21:55:21Z

+            try:
+                env = self.acquire_license(timeout=timeout)
+                if env is None:
+                    self._license_cache = LicenseAvailability.Timeout


It is hard to distinguish between a timeout and no license... It looks like it is possible to return Timeout when the result should actually be NotAvailable?

I messed with this one a lot and am 1000% not sure what the right thing to do is. So basically, if acquire_license times out, it is guaranteed to return None. I think otherwise, it will error. But I was having a hard time testing to ensure that that did actually happen.

michaelbynum · 2025-09-17T21:57:31Z

+                if env is None:
+                    self._license_cache = LicenseAvailability.Timeout
+                    return self._license_cache
+            except gurobipy.GurobiError as acquire_error:


Is it possible to hit this exception? It looks like acquire_license is guarded with try statements in a way that this code cannot be reached?

Ooo. That's a good point. What about this instead?

if not timeout: try: cls._gurobipy_env = gurobipy.Env() except gurobipy.GurobiError: # Re-raise so license_available can inspect further # or so users can explicitly view the error raise return cls._gurobipy_env

That looks good, but I'm not sure there is a point to the try statement at this point???

The only thing I see that might be useful here is, "What if there is some other type of exception that isn't a GurobiError?" - In that case, we are just returning None. But do we want to do that? Is it better if we just let it explode?

Sorry - I was not clear. I mean the try statement in acquire_license, not the try statement here.

michaelbynum · 2025-09-17T22:06:10Z

+            except gurobipy.GurobiError as large_error:
+                msg = str(large_error).lower()
+                status = getattr(large_error, "errno", None)
+                if "too large" in msg or status in (10010,):
+                    self._license_cache = LicenseAvailability.LimitedLicense
+                elif "queue" in msg or "timeout" in msg:
+                    self._license_cache = LicenseAvailability.Timeout
+                elif (
+                    "no gurobi license" in msg
+                    or "not licensed" in msg
+                    or status in (10009,)
+                ):
+                    self._license_cache = LicenseAvailability.NotAvailable
+                else:
+                    self._license_cache = LicenseAvailability.BadLicense


Once we have gotten here, don't we know that the result should be LimitedLicense? Is anything else possible?

I think a timeout or "some other unknown thing" is possible. But not NotAvailable, you're right. What about this?

try: # We try a 'big' model (more than 2000 vars). # This should give us all the information we need # about the license status. large_model = gurobipy.Model(env=env) large_model.addVars(range(2001)) large_model.optimize() self._license_cache = LicenseAvailability.FullLicense except gurobipy.GurobiError as large_error: msg = str(large_error).lower() status = getattr(large_error, "errno", None) if "too large" in msg or status in (10010,): self._license_cache = LicenseAvailability.LimitedLicense elif "queue" in msg or "timeout" in msg: self._license_cache = LicenseAvailability.Timeout else: self._license_cache = LicenseAvailability.Unknown finally: large_model.dispose()

Looks good, I think.

michaelbynum · 2025-09-17T22:08:34Z

        self._vars_added_since_update = ComponentSet()
        self._last_results_object: Optional[Results] = None

+    def close(self):


What motivated this new method?

See the comment below on release_license - because I made a classmethod version, there was a naming clash, so I needed a bit of a hack to get around it.

michaelbynum · 2025-09-19T13:12:19Z

+            try:
+                cls._gurobipy_env = gurobipy.Env()
+            except gurobipy.GurobiError:
+                # Re-raise so license_available can inspect further
+                # or so users can explicitly view the error
+                raise


This is what I am talking about. This try statement does not seem to do anything except raise any exception that gets raised???

michaelbynum

My remaining comments don't really matter. I'm happy at this point.

mrmundt · 2025-10-03T13:13:32Z

I'm re-working this one, so closing

mrmundt added 3 commits September 16, 2025 13:40

Separate available and license_available

f76547b

Add some availability tests

6d18061

Clean up some docs

8139343

mrmundt requested review from blnicho, jsiirola and michaelbynum September 16, 2025 20:34

mrmundt mentioned this pull request Sep 16, 2025

[PEP] Next Steps for Solver Interface Redesign #3688

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michaelbynum reviewed Sep 16, 2025

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mrmundt added 4 commits September 16, 2025 16:16

Simplify the license check

9ada68a

Rework to solver_available, license_available, and available

ebfc130

Direct license check no longer necessary

69d7afe

Update tests to ensure correct behavior; actually add minimal gurobi_…

e13e10f

…direct tests

mrmundt changed the title ~~Separate available and license_available~~ Separate solver_available and license_available Sep 17, 2025

Missed a docstring update

190bf09

mrmundt requested a review from michaelbynum September 17, 2025 20:33

mrmundt added 3 commits September 17, 2025 14:53

Look, the tests caught a bug

799739d

Add log message if timeout achieved; set LicenseAvailability explicitly

ccab516

Fix docstrings

6fc3fcb

michaelbynum requested changes Sep 17, 2025

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Address michaelbynum's comments

0c57d1a

mrmundt requested a review from michaelbynum September 18, 2025 17:02

michaelbynum reviewed Sep 19, 2025

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michaelbynum approved these changes Sep 19, 2025

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mrmundt closed this Oct 3, 2025

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mrmundt commented Sep 16, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Fixes None (but is part of #3688)

Summary/Motivation:

Changes proposed in this PR:

Legal Acknowledgement

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mrmundt Sep 18, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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mrmundt Sep 18, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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mrmundt commented Oct 3, 2025

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mrmundt commented Sep 16, 2025 •

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mrmundt Sep 18, 2025 •

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