Add dense and sparse wrappers for ParOpt from ParOpt directly

[gjkennedy]

Purpose

This PR adds the ParOpt sparse and dense constraint wrappers for pyOptSparse from ParOpt directly.

Expected time until merged

Type of change

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (non-backwards-compatible fix or feature)
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Documentation update
• Maintenance update
• Other (please describe)

Testing

Checklist

• I have run flake8 and black to make sure the Python code adheres to PEP-8 and is consistently formatted
• I have formatted the Fortran code with fprettify or C/C++ code with clang-format as applicable
• I have run unit and regression tests which pass locally with my changes
• I have added new tests that prove my fix is effective or that my feature works
• I have added necessary documentation

[A-CGray]

@marcomangano @ewu63 the actual pyoptsparse wrapper that this will end up using is here

[A-CGray]

The tests are failing because our docker images are pinned to an older version of ParOpt. But if we update the ParOpt version in the docker images before merging this PR then the image builds will fail and so the tests here will still fail. So I guess we need to test this PR locally, merge it even with failing azure tests, and then update the docker images. Opinions @ewu63 @eirikurj ?

[A-CGray]

@gjkennedy I've run the pyoptsparse tests locally, the dense version of your wrapper seems to work fine, but when using the sparse version the constraints seem to be ignored if you use the trust region algorithm which is the default, interior-point and mma work fine. Try running test_hs015.py

[marcomangano]

Specific test errors aside, I have mixed feelings about moving the actual pyOptSparse wrapper to the parOpt repo.

On the one hand, outsourcing it could make things a bit easier for us in terms of maintenance, especially if the SMDO group plans to update the python API on a regular basis.
On the other hand, if we make breaking changes to our codebase, we would not be able to address it directly and have to wait for a new version release of ParOpt for our tests to pass. Since we run tests on our side, I am leaning towards moving the updated wrapper back here.

This would also avoid the kind of "circular import" happening now, where pyoptsparse imports paropt but the imported wrapper is also importing pyoptsparse components - but this is a minor note.
Curious to hear @ewu63 and @eirikurj take on this.

[ewu63]

1. I have no idea how this circular dependency would be resolved, and in any case I don't think pyoptsparse-specific code should live in ParOpt. Instead, a generic Python interface should be provided. I think the correct approach would be the following, consistent with our other wrappers
   1. Keep the wrapper in this repo
   2. Test with specific tagged version, and request that changes to API be versioned appropriately
2. Once the wrapper is confirmed to be working, we can merge this PR and then update docker. The procedure you described is fine @A-CGray

[gjkennedy]

Hey guys, this is a PR. Feel free to accept or reject it. Do not feel free to copy code from the wrapper I wrote into your repo! Thanks!

[A-CGray]

@gjkennedy we can go with this approach, but there are currently some issues with the wrapper in the ParOpt. I opened smdogroup/paropt#51 to fix them. With those fixes I can get the paropt tests in this repo to pass. Once that PR is merged and you make a new release of ParOpt, we can figure out how to get things working in our docker images.

@ewu63 , the MPI environment variable tests below are now failing because this PR removed this code, I had a look at adding it back but I can't understand the logic behind the code, could you take a look?

pyoptsparse/tests/test_require_mpi_env_var.py

Lines 45 to 73 in f66e9fb

	class TestRequireMPIEnvVarOnParOpt(unittest.TestCase):
	# Check how the environment variable affects using ParOpt
	def setUp(self):
	# Just check to see if ParOpt is installed before doing any testing
	try:
	from paropt import ParOpt as _ParOpt # noqa: F401
	except ImportError:
	raise unittest.SkipTest("Optimizer not available: paropt")
	def test_require_mpi_check_paropt(self):
	os.environ["PYOPTSPARSE_REQUIRE_MPI"] = "1"
	import pyoptsparse.pyParOpt.ParOpt
	importlib.reload(pyoptsparse.pyParOpt.ParOpt)
	self.assertIsNotNone(pyoptsparse.pyParOpt.ParOpt._ParOpt)
	def test_no_mpi_requirement_given_check_paropt(self):
	os.environ.pop("PYOPTSPARSE_REQUIRE_MPI", None)
	import pyoptsparse.pyParOpt.ParOpt
	importlib.reload(pyoptsparse.pyParOpt.ParOpt)
	self.assertIsNotNone(pyoptsparse.pyParOpt.ParOpt._ParOpt)
	def test_do_not_use_mpi_check_paropt(self):
	os.environ["PYOPTSPARSE_REQUIRE_MPI"] = "0"
	import pyoptsparse.pyParOpt.ParOpt
	importlib.reload(pyoptsparse.pyParOpt.ParOpt)
	self.assertTrue(isinstance(pyoptsparse.pyParOpt.ParOpt._ParOpt, str))