Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

[PEP] Redesign of Pyomo Solvers #1030

Open
michaelbynum opened this issue May 23, 2019 · 18 comments · Fixed by #3137
Open

[PEP] Redesign of Pyomo Solvers #1030

michaelbynum opened this issue May 23, 2019 · 18 comments · Fixed by #3137
Assignees

Comments

@michaelbynum
Copy link
Contributor

michaelbynum commented May 23, 2019

I would like to start redesigning the solver interfaces in Pyomo.

Motivation

  1. The current solver interfaces are more complex than necessary.
  2. The current solver interfaces have many inconsistencies.
  3. The current solver interfaces do not allow the solution of a model/block with constraints that use variables which live elsewhere.

Preliminary Design Decisions (to be updated with time)

  • When solving a model/block, the model is defined by the set of active components and any components used by those active components. This means that variables are handed to the solver if and only if they are used in an active constraint or objective.

Implementation

  • I intend to develop new solver interfaces alongside the existing ones. I do not intend to remove existing solver interfaces. Once the new solver interfaces are sufficiently mature, we can rename/archive the old interfaces.
  • I intend to start with a couple simple solver interfaces and get feedback before proceeding further.

Thoughts? Concerns?

Related Issues

@michaelbynum michaelbynum self-assigned this May 23, 2019
@ghackebeil
Copy link
Member

I think you should reduce the scope of this PEP. The third bullet point is an orthogonal and controversial issue. There is no need to have it possibly get in the way the other (much needed) changes.

@jwatsonnm
Copy link
Contributor

Regarding the third bullet Gabe references, can you clarify? Is said variable at least below the current block in the model component hierarchy? If it's not in the hierarchy, then I agree with Gabe that this is highly controversial.

@carldlaird
Copy link
Member

I updated the motivation in the pep to have numbers.

It would be good to document the cases where "Bullet 3" is required. I also admit that the first time I heard that we needed to support solves where variables live outside the hierarchy, I thought this was very strange because it breaks encapsulation of sub-models. Having said that, I would like to see a use case where this is required to be convinced one way or another.

@michaelbynum
Copy link
Contributor Author

@ghackebeil @jwatsonnm I will open a separate PEP for (3).

@michaelbynum
Copy link
Contributor Author

@ghackebeil @jwatsonnm @carldlaird Let's move the discussion of (3) to #1032.

@DLWoodruff
Copy link
Contributor

Now that the controversy has moved to #1032, I predict that everyone will think the new PEP with only items one and two is non-controversial great idea and that you should proceed with your plan to create a couple of examples.

@jsiirola
Copy link
Member

I am adding a performance label to this PEP. I believe that a redesign of the base solver API is a prerequisite before we can (effectively) tackle things like reworking the writers / readers / persistent APIs.

@jsiirola
Copy link
Member

jsiirola commented May 8, 2020

Archived on the master Performance Proposals Issue (#1430). Not closing as this is also marked as a PEP.

@alexchandel
Copy link

It would be very useful to users to define one or more base protocols or base classes that all solvers inherit from. Many solvers like the BARON shell interface inherit from opt.base.solvers.OptSolver. However, several solver managers including GAMS and AsynchronousActionManager and MindtPySolver do not. This causes problems like #2757, where users expect options= to work and it doesn't.

It would be best to factor out some standard behavior, like supporting the options= keyword to set .options.

Also, for example, all solvers seem to implement a solve method, and many have a license_is_valid method. Defining such methods in an abstract base class or protocol would help users keep track of what solvers can even do.

@mrmundt
Copy link
Contributor

mrmundt commented Aug 30, 2023

@alexchandel - Agreed. All of those considerations are on our list.

@alexchandel
Copy link

I would add to this—because the "results" of a Pyomo solver are part of the solver's API—to standardize at least SOME of the SolverResults structure across all solvers.

In particular, indicate in universal fashion whether the result was a solution, or infeasible/failure. See #2942 for an example where this behavior is inconsistent between solvers, preventing universal client code from being written.

@alexchandel
Copy link

I would add an additional motivation for base classes is the recent emergence of powerful Python type checkers like Pylance/Pyright and mypy. Unfortunately some of Pyomo is extremely dynamic, and currently difficult for type checkers to work out (e.g. #2078, #2821, #2938). However, it would be nice for the construction SolverFactory(backend.str()) to be known to return a subclass of a known base class with a .solve() method, and similarly for SolverManagerFactory(backend.str()).

@alexchandel
Copy link

Additionally, the Pyomo solver interface needs a common exception for when a Solver is not available. Observe the extremely different behavior when calling solve() on two solvers, neither of which is available:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/Users/alex/test/test.py", line 3370, in start
    main()
…
  File "/Users/alex/test/.venv/lib/python3.11/site-packages/pyomo/solvers/plugins/solvers/GAMS.py", line 766, in solve
    self.available()
  File "/Users/alex/test/.venv/lib/python3.11/site-packages/pyomo/solvers/plugins/solvers/GAMS.py", line 654, in available
    raise NameError(
NameError: No 'gams' command found on system PATH - GAMS shell solver functionality is not available.
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/Users/alex/test/test.py", line 3370, in start
    main()
…
  File "/Users/alex/test/.venv/lib/python3.11/site-packages/pyomo/opt/base/solvers.py", line 533, in solve
    self.available(exception_flag=True)
  File "/Users/alex/test/.venv/lib/python3.11/site-packages/pyomo/opt/solver/shellcmd.py", line 141, in available
    raise ApplicationError(msg % self.name)
pyomo.common.errors.ApplicationError: No executable found for solver 'baron'

@blnicho
Copy link
Member

blnicho commented Nov 14, 2023

Linking to issue #728. It would be nice if this utility for extracting info from the Ipopt log could be incorporated into the redesigned Ipopt interface.

@mrmundt
Copy link
Contributor

mrmundt commented Jan 3, 2024

Linking to issue #7

@mrmundt
Copy link
Contributor

mrmundt commented Feb 21, 2024

To do for Part 2:

jsiirola added a commit to jsiirola/pyomo that referenced this issue Feb 21, 2024
@emma58
Copy link
Contributor

emma58 commented Feb 21, 2024

I think the second bullet should be two different things:

  1. shift name and type to two different values such as interface and algorithm, and
  2. Generalize (and perhaps rename?) solver_options to handle case where multiple subsolvers are involved, all of which could have their own options.

@FBumann
Copy link

FBumann commented Dec 15, 2024

Im really looking forward to this!!!

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment