Optimize select() statements by removing redundant conditions

[MaxGhenis]

Summary

Optimizes all np.select() statements in the codebase by removing conditions that return the same value as the default. This is the numpy-efficient pattern where the default handles the most common case(s).

Key insight: When using np.select(), each condition requires an array comparison. By setting default= to the most common value and removing explicit conditions for that value, we reduce evaluations from N to N-k.

Example optimization (taxsim_mstat.py)

Before:

return select(
    [
        filing_status == fstatus.SINGLE,
        filing_status == fstatus.HEAD_OF_HOUSEHOLD,
        filing_status == fstatus.JOINT,
        filing_status == fstatus.SEPARATE,
        filing_status == fstatus.SURVIVING_SPOUSE,
    ],
    [1, 1, 2, 6, 8],
)

After:

return select(
    [
        filing_status == fstatus.JOINT,
        filing_status == fstatus.SEPARATE,
        filing_status == fstatus.SURVIVING_SPOUSE,
    ],
    [2, 6, 8],
    default=1,  # SINGLE, HEAD_OF_HOUSEHOLD
)

Changes

• 56 files modified across federal and state tax/benefit calculations
• Net +27 lines (added clarifying comments documenting what defaults cover)
• Common pattern: SINGLE filing status as default for state income tax calculations
• Special cases: taxsim_mstat (SINGLE + HOH → 1), age_group (WORKING_AGE as default)

Performance benefit

Each removed condition eliminates one boolean array comparison per element. For microsimulations with millions of tax units, this reduces memory allocations and CPU cycles.

Test plan

• All 56 modified files pass Python syntax validation
• Package imports successfully
• CI tests pass

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.97%. Comparing base (7e781d3) to head (399c93a).
⚠️ Report is 25 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##              main    #7242      +/-   ##
===========================================
- Coverage   100.00%   98.97%   -1.03%     
===========================================
  Files           12       16       +4     
  Lines          205      294      +89     
  Branches         0        3       +3     
===========================================
+ Hits           205      291      +86     
- Misses           0        3       +3     

Flag	Coverage Δ
unittests	98.97% <ø> (-1.03%)	⬇️

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[MaxGhenis]

Optimization suggestion: Remove redundant conditions

When using np.select, the most efficient pattern is to have the default handle the most common case, allowing us to remove the explicit conditions for values that match the default. This reduces the number of condition evaluations.

taxsim_mstat.py

SINGLE and HEAD_OF_HOUSEHOLD both return 1. Since these are likely the most common, use 1 as default and remove their conditions:

return select(
    [
        filing_status == fstatus.JOINT,
        filing_status == fstatus.SEPARATE,
        filing_status == fstatus.SURVIVING_SPOUSE,
    ],
    [
        2,
        6,
        8,
    ],
    default=1,  # SINGLE, HEAD_OF_HOUSEHOLD
)

age_group.py

WORKING_AGE is the default and most common. Remove that condition:

return select(
    [
        person("is_child", period),
        person("is_senior", period),
    ],
    [AgeGroup.CHILD, AgeGroup.SENIOR],
    default=AgeGroup.WORKING_AGE,
)

mt_capital_gains_tax_indiv.py

SINGLE rates are the default. Remove those conditions from both selects:

lower_rate = select(
    [
        filing_status == status.SEPARATE,
        filing_status == status.SURVIVING_SPOUSE,
        filing_status == status.HEAD_OF_HOUSEHOLD,
    ],
    [
        p.rates.separate.amounts[0],
        p.rates.surviving_spouse.amounts[0],
        p.rates.head_of_household.amounts[0],
    ],
    default=p.rates.single.amounts[0],
)

(Same pattern for higher_rate)

mt_capital_gains_tax_applicable_threshold_indiv.py

Same optimization - remove the SINGLE condition since it's the default.

ia_standard_deduction_indiv.py and ia_amt_indiv.py

Remove the SINGLE condition since default=fsvals.SINGLE.

This pattern reduces condition evaluations from N to N-k where k is the number of conditions that match the default value.

[MaxGhenis]

/rebase