Operators from Binf to Box constraints

[arnavk23]

This PR successfully generalizes shifted proximal operators from Binf (L∞-ball) constraints to Box constraints, enabling support for arbitrary box bounds [l, u] while maintaining backward compatibility with symmetric constraints [-Δ, Δ].

Key Changes

Enhanced existing Box variants (ShiftedIndBallL0Box, ShiftedGroupNormL2Box) with dual signature support for both general and symmetric constraints
Added backward compatibility layer that automatically returns Box variants for legacy Binf signatures
Updated test references and type expectations to match the new Box variant signatures

Continues from #144, #148, #147
Fixes #88

[arnavk23]

@dpo Fixed issues in tests, like allocations which are causing error also in Maxence's pr as mentioned here #150 (comment)

[MaxenceGollier]

I am not sure to understand the point of this PR.
Are you trying to remove allocations or to fix #88 ?
Moreover, you can not fix tests by letting the operators allocate.

[Copilot]

Pull request overview

This PR generalizes shifted proximal operators from Binf (L∞-ball) constraints to Box constraints, enabling support for arbitrary box bounds [l, u]. The changes maintain backward compatibility by providing adapter methods that convert legacy Binf signatures (Δ, χ) to the new Box constraint format [-Δ, Δ]. Additionally, the PR includes performance optimizations across several operators to reduce allocations.

Key changes:

• Introduced ShiftedIndBallL0Box and ShiftedGroupNormL2Box as generalized Box constraint operators
• Added backward compatibility methods in the new Box files to handle legacy Binf signatures
• Removed includes for old Binf files from the main module while keeping the files in the repository
• Applied allocation-reducing optimizations to SVD-based operators and other performance-critical paths

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/ShiftedProximalOperators.jl	Replaced Binf file includes with Box file includes; added property accessors for backward compatibility; optimized function evaluation
src/shiftedIndBallL0Box.jl	New file implementing generalized Box constraints for IndBallL0 with backward compatibility methods
src/shiftedGroupNormL2Box.jl	New file implementing generalized Box constraints for GroupNormL2/NormL2 with backward compatibility methods
src/shiftedIndBallL0BInf.jl	Removed the legacy shifted() constructor (moved to Box variant)
src/shiftedGroupNormL2Binf.jl	Removed legacy shifted() constructors (moved to Box variants); optimized prox! to reduce allocations
src/shiftedNormL1B2.jl	Refactored prox! for reduced allocations and improved numerical stability
src/shiftedRank.jl	Optimized prox! with in-place operations to avoid temporaries
src/shiftedNuclearnorm.jl	Optimized prox! with in-place operations to avoid temporaries
src/Nuclearnorm.jl	Optimized prox! with copyto! and in-place operations
src/psvd.jl	Removed complex number divide-and-conquer SVD implementations; fixed type conversion and various bugs; moved psvd() function
test/test_allocs.jl	Updated macro and switched from @allocated to @wrappedallocs for more accurate allocation testing
test/runtests.jl	Updated test expectations to use Box variants; added comprehensive tests for new Box operators; adjusted tolerance for numerical comparisons

Comments suppressed due to low confidence (3)

src/psvd.jl:466

• The complex number SVD implementations for the divide-and-conquer algorithm (psvd_workspace_dd and psvd_dd! for ComplexF32 and ComplexF64) were completely removed from the file. However, the complex number implementations for QRIteration algorithm remain. This creates an asymmetry where complex matrices can only use QRIteration algorithm but not the divide-and-conquer algorithm. If this is intentional, it should be documented. If not, this is a breaking change that removes functionality.

    end
  end
end

src/ShiftedProximalOperators.jl:160

• When accessing ψ.Δ on a Box variant with vector bounds where elements have different symmetric constraints (e.g., l = [-0.5, -0.3], u = [0.5, 0.3]), this code will return u[1] (0.5) even though the second element has a different radius (0.3). This is incorrect and could lead to silent bugs. The code should either error for non-uniform bounds or return the vector of radii.

fun_expr(ψ::ShiftedProximableFunction) = "t ↦ h(xk + sj + t)"
fun_params(ψ::ShiftedProximableFunction) = "xk = $(ψ.xk)\n" * " "^14 * "sj = $(ψ.sj)"

src/ShiftedProximalOperators.jl:170

• Returning a dummy Conjugate(IndBallL1(1.0)) for Box variants when accessing ψ.χ is misleading and could cause subtle bugs. The actual constraints are Box constraints with bounds [l, u], not L∞-ball constraints with conjugate IndBallL1. If the χ field doesn't exist on Box variants, accessing it should either error clearly or return a value that accurately represents the constraints.

  show(io, ψ.h)
end

"""

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