Interface to GiNaC for Simplification

[michaelbynum]

Summary/Motivation:

This PR provides an interface to GiNaC for expression simplification (although sympy can be used as well).

In [1]: import pyomo.environ as pe

In [2]: from pyomo.core.expr import differentiate

In [3]: from pyomo.contrib.simplification import Simplifier

In [4]: from pyomo.contrib.fbbt.fbbt import compute_bounds_on_expr

In [5]: m = pe.ConcreteModel()
   ...: m.x = pe.Var(bounds=(0, None))
   ...: e = m.x * pe.log(m.x)

In [6]: der1 = differentiate(e, m.x, mode=differentiate.Modes.reverse_symbolic)
   ...: der2 = differentiate(der1, m.x, mode=differentiate.Modes.reverse_symbolic)

In [7]: simp = Simplifier()

In [8]: der2_simp = simp.simplify(der2)

In [9]: print(der2)
1/x - x/x**2 + 1/x

In [10]: print(der2_simp)
x**-1.0

In [11]: compute_bounds_on_expr(der2_simp)
Out[11]: (0.0, None)

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.

[michaelbynum]

Okay, I think tests will pass now. The GiNaC interface is only tested under "singletest" because it takes a while to install GiNaC.

[codecov[bot]]

Codecov Report

Attention: 50 lines in your changes are missing coverage. Please review.

Comparison is base (85b63ab) 88.26% compared to head (125b7c7) 88.22%. Report is 87 commits behind head on main.

Files	Patch %	Lines
pyomo/contrib/simplification/build.py	18.33%	49 Missing :warning:
pyomo/contrib/simplification/simplify.py	97.36%	1 Missing :warning:

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[dallan-keylogic]

FWIW, I got directed to this PR by John Siirola, and had an error:

Traceback (most recent call last):
  File "C:\Users\[REDACTED]\.conda\envs\idaes\lib\pdb.py", line 1723, in main
    pdb._runscript(mainpyfile)
  File "C:\Users\[REDACTED]\.conda\envs\idaes\lib\pdb.py", line 1583, in _runscript
    self.run(statement)
  File "C:\Users\[REDACTED]\.conda\envs\idaes\lib\bdb.py", line 598, in run
    exec(cmd, globals, locals)
  File "<string>", line 1, in <module>
  File "c:\users\[REDACTED]\repos\cesar_1\enrtl\enthalpy_validation_local_3.py", line 96, in <module>
    diff = simp.simplify(
  File "c:\users\[REDACTED]\repos\pyomo\pyomo\contrib\simplification\simplify.py", line 65, in simplify
    return simplify_with_sympy(expr)
  File "c:\users\[REDACTED]\repos\pyomo\pyomo\contrib\simplification\simplify.py", line 32, in simplify_with_sympy
    se = se.simplify()
AttributeError: 'int' object has no attribute 'simplify'
Uncaught exception. Entering post mortem debugging
Running 'cont' or 'step' will restart the program
> c:\users\[REDACTED]\repos\pyomo\pyomo\contrib\simplification\simplify.py(32)simplify_with_sympy()
-> se = se.simplify()
(Pdb) print(se)
0

I see now that I didn't end up installing GiNaC, so that's why it's using Sympy, but thought I should let you know about the issue in the present implementation.

Edit: Is there any tutorial about how to install GiNaC and make it available to Pyomo? I see there's parts of the PR to add GiNaC install to the CI, but I'm not sure how to translate that to my (Windows) machine.

[michaelbynum]

@dallan-keylogic - Thanks! Should be fixed now. Please let me know if my fix did not actually fix the problem.

Let me get back to you on installation.

[michaelbynum]

@dallan-keylogic, I don't have any better installation instructions than what is here: https://www.ginac.de/Download.html. Once you have GiNaC installed, you need to make sure the libraries and header files for both CLN and GiNaC are "findable". Ultimately those get used here: https://github.com/michaelbynum/pyomo/blob/1b1f944dbd00ca0e0b27d2fd2b70ee681b8e44ae/pyomo/contrib/simplification/build.py#L60.

[dallan-keylogic]

Unfortunately that fix didn't work:

Traceback (most recent call last):
  File "C:\Users\[REDACTED]\.conda\envs\idaes\lib\pdb.py", line 1723, in main
    pdb._runscript(mainpyfile)
  File "C:\Users\[REDACTED]\.conda\envs\idaes\lib\pdb.py", line 1583, in _runscript
    self.run(statement)
  File "C:\Users\[REDACTED]\.conda\envs\idaes\lib\bdb.py", line 598, in run
    exec(cmd, globals, locals)
  File "<string>", line 1, in <module>
  File "c:\users\[REDACTED]\repos\cesar_1\enrtl\enthalpy_validation_local_3.py", line 96, in <module>
    diff = simp.simplify(
  File "c:\users\[REDACTED]\repos\pyomo\pyomo\contrib\simplification\simplify.py", line 69, in simplify
    return simplify_with_sympy(expr)
  File "c:\users\[REDACTED]\repos\pyomo\pyomo\contrib\simplification\simplify.py", line 34, in simplify_with_sympy
    se = se.simplify()
AttributeError: 'int' object has no attribute 'simplify'
Uncaught exception. Entering post mortem debugging
Running 'cont' or 'step' will restart the program
> c:\users\[REDACTED]\repos\pyomo\pyomo\contrib\simplification\simplify.py(34)simplify_with_sympy()
-> se = se.simplify()
(Pdb) is_constant(se)
True
(Pdb) is_constant(expr_
*** SyntaxError: '(' was never closed
(Pdb) is_constant(expr)
False
(Pdb) expr
<pyomo.core.base.expression.ExpressionData object at 0x0000022960608880>
(Pdb) expr.pprint()
{Member of Liq_dalpha_dT} : Non-randomness parameters
    Size=28, Index=params.true_species_set*params.true_species_set
    Key            : Expression
    ('H2O', 'H2O') :        0.0
(Pdb) expr.is_constant()
False
(Pdb) type(expr)
<class 'pyomo.core.base.expression.ExpressionData'>

It looks like is_constant always returns false for ExpressionData.

Let me try installing GiNaC and get back to you on that.

[dallan-keylogic]

The link for Windows builds of GiNaC is broken, so that probably ends this experiment for me.

[michaelbynum]

@jsiirola, should sympyify_expression convert mutable parameters to sympy symbols like it does for variables? I think this is what is causing @dallan-keylogic's error (not 100% sure).

[michaelbynum]

Another question for @jsiirola - right now, the simplification logic using sympy will remove mutable parameters from the expression. I'm not sure how I feel about that. I don't really know what the expected behavior should be. Thoughts?

[dallan-keylogic]

Unfortunately, in my current model I have some "mutable" parameters that are equal to zero and that I never want to change, but they're forced to be mutable because they have units. I think that AD is fixed so I could just turn them into 0 multiplied by units, though.

[michaelbynum]

There seem to be issues with get_tar_archive on windows

[michaelbynum]

Thanks for all the help on this one, @jsiirola.

[michaelbynum]

@dallan-keylogic, I believe we did fix the mutable parameter issue as part of the PR (with the sympy interface).