Experimental Support for Grouping Algebraic Patterns in Constraints and Objectives

[pulsipher]

This adds experimental support of detecting common constraint /objective patterns, grouping them together, and adding each group as a single ExaModels.Constraint or objective term. Given model::InfiniteModel, the user syntax is simply:

em = ExaModel(model, group_repeated_algebraic_patterns = true)

or

optimize!(model, group_repeated_algebraic_patterns = true) # assumes backend is an `ExaTranscriptionBackend`

Support is limited to:

• Constraints without measures
• Constraints patterns with the same infinite parameters
• Finite sums inside of objective measures that operate on nonlinear functions (i.e., need to use @force_nonlinear)

These restrictions could be overcome in the future, but that would be in separate PR.

The support for objectives is exemplified by the following case:

@objective(m, Min, integral(sum(@force_nonlinear((y[i] - 2)^2) for i in 1:4), t)

Note how sum is inside the integral measure and how @force_nonlinear is used for the expression inside the sum.

Early testers can try this out via:

import Pkg
Pkg.add(url="https://github.com/infiniteopt/InfiniteExaModels.jl", rev = "template_constraints")

Possible improvements include:

• Detecting repeated patterns across all constraints
• Taking advantage of repeated patterns in derivative equations and collocation restrictions
• Handing finite indexing with unregistered variables (e.g., derivatives)
• Handling indexed infinite parameters (beyond scope, requires variables with sparse indexing)
• Removing recursion (beyond scope, ExaModels is not well-suited for deeply nested exprs)
• Removing unnecessary asserts (keep for now just to be save)
• Handling constraints with measures (beyond scope, measures deserve their own PR)
• Investigating how this might apply to objective functions
• Improving the info printing, especially during this experimental phase

[codecov-commenter]

Codecov Report

❌ Patch coverage is 98.46939% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.10%. Comparing base (782b4c3) to head (bb63aa4).

Files with missing lines	Patch %	Lines
src/transform.jl	97.40%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #44      +/-   ##
==========================================
+ Coverage   85.99%   91.10%   +5.10%     
==========================================
  Files           6        7       +1     
  Lines         757     1057     +300     
==========================================
+ Hits          651      963     +312     
+ Misses        106       94      -12     

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