feat: Add Method of Equal Shares #599

fsargent · 2024-07-14T05:41:00Z

Context:

This pull request adds new test cases for the MethodOfEqualShares class within the packages/backend/src/Tabulators/MethodOfEqualShares.ts file. This includes importing the fraction.js package and several testing scenarios such as Basic Example, Influence Budget Redistribution, Random Tiebreaker, Random Tiebreaker with Defined Order, and Valid/Invalid/Under/Bullet Vote Counts.

Key Changes:

New test file:
- Created a new test file at packages/backend/src/Tabulators/MethodOfEqualShares.test.ts.
- Added comprehensive test cases to validate the functionality of the MethodOfEqualShares.
Implementation of MethodOfEqualShares
- Added packages/backend/src/Tabulators/MethodOfEqualShares.ts to implement the MethodOfEqualShares function.
- The function calculates election results based on various voting methods and scenarios.
- It handles tiebreakers, influence budget redistribution, and validates different vote types.

Testing Instructions:

Run the test suite in the packages/backend/ directory to ensure all new and existing tests pass.

Motivation:

To ensure the reliability and accuracy of the MethodOfEqualShares function.
To handle edge cases and validate the workflow of the election model.

**Context:** This pull request adds new test cases for the `MethodOfEqualShares` class within the `packages/backend/src/Tabulators/MethodOfEqualShares.ts` file. This includes importing the `fraction.js` package and several testing scenarios such as Basic Example, Influence Budget Redistribution, Random Tiebreaker, Random Tiebreaker with Defined Order, and Valid/Invalid/Under/Bullet Vote Counts. **Key Changes:** 1. **New test file:** - Created a new test file at `packages/backend/src/Tabulators/MethodOfEqualShares.test.ts`. - Added comprehensive test cases to validate the functionality of the `MethodOfEqualShares`. 2. **Implementation of MethodOfEqualShares** - Added `packages/backend/src/Tabulators/MethodOfEqualShares.ts` to implement the MethodOfEqualShares function. - The function calculates election results based on various voting methods and scenarios. - It handles tiebreakers, influence budget redistribution, and validates different vote types. **Testing Instructions:** - Run the test suite in the `packages/backend/` directory to ensure all new and existing tests pass. **Motivation:** - To ensure the reliability and accuracy of the `MethodOfEqualShares` function. - To handle edge cases and validate the workflow of the election model.

fsargent · 2024-07-18T17:59:00Z


 FAIL  src/Tabulators/MethodOfEqualShares.test.ts
  Method of Equal Shares Tests
    ✓ Basic Example (3 ms)
    ✓ Basic Example 2
    ✕ Basic Example 3 (3 ms)
    ✓ Influence Budget Redistribution
    ✓ Random Tiebreaker (1 ms)
    ✓ Random Tiebreaker with Defined Order (1 ms)
    ✓ Valid/Invalid/Under/Bullet Vote Counts (1 ms)

  ● Method of Equal Shares Tests › Basic Example 3

    expect(received).toBe(expected) // Object.is equality

    Expected: "Grace"
    Received: "Frank"

      81 |     expect(results.elected[0].name).toBe("Allison");
      82 |     expect(results.elected[1].name).toBe("Bill");
    > 83 |     expect(results.elected[2].name).toBe("Grace");
         |                                     ^
      84 |     expect(results.elected[3].name).toBe("Jack");
      85 |     expect(results.elected[4].name).toBe("Mona");
      86 |     expect(results.elected[5].name).toBe("Oscar");

      at Object.<anonymous> (src/Tabulators/MethodOfEqualShares.test.ts:83:37)

Test Suites: 1 failed, 1 total
Tests:       1 failed, 6 passed, 7 total
Snapshots:   0 total
Time:        2.183 s, estimated 3 s

Not sure why this is failing...

 {
      candidates: [
        { index: 0, name: 'Allison', tieBreakOrder: 0 },
        { index: 1, name: 'Bill', tieBreakOrder: 1 },
        { index: 2, name: 'Carmen', tieBreakOrder: 2 },
        { index: 3, name: 'Doug', tieBreakOrder: 3 },
        { index: 4, name: 'Eve', tieBreakOrder: 4 },
        { index: 5, name: 'Frank', tieBreakOrder: 5 },
        { index: 6, name: 'Grace', tieBreakOrder: 6 },
        { index: 7, name: 'Hank', tieBreakOrder: 7 },
        { index: 8, name: 'Ivy', tieBreakOrder: 8 },
        { index: 9, name: 'Jack', tieBreakOrder: 9 },
        { index: 10, name: 'Karen', tieBreakOrder: 10 },
        { index: 11, name: 'Leo', tieBreakOrder: 11 },
        { index: 12, name: 'Mona', tieBreakOrder: 12 },
        { index: 13, name: 'Nina', tieBreakOrder: 13 },
        { index: 14, name: 'Oscar', tieBreakOrder: 14 },
        { index: 15, name: 'Paul', tieBreakOrder: 15 },
        { index: 16, name: 'Quinn', tieBreakOrder: 16 },
        { index: 17, name: 'Rita', tieBreakOrder: 17 },
        { index: 18, name: 'Sam', tieBreakOrder: 18 }
      ],
      totalScores: [
        { index: 0, score: 6 },
        { index: 1, score: 6 },
        { index: 2, score: 4 },
        { index: 3, score: 5 },
        { index: 4, score: 5 },
        { index: 5, score: 6 },
        { index: 6, score: 7 },
        { index: 7, score: 5 },
        { index: 8, score: 5 },
        { index: 9, score: 6 },
        { index: 10, score: 2 },
        { index: 11, score: 5 },
        { index: 12, score: 6 },
        { index: 13, score: 4 },
        { index: 14, score: 6 },
        { index: 15, score: 3 },
        { index: 16, score: NaN },
        { index: 17, score: NaN },
        { index: 18, score: NaN }
      ],
      nValidVotes: 10,
      nInvalidVotes: 0,
      nUnderVotes: 0,
      nBulletVotes: 0
    }

mikefranze · 2024-07-19T21:37:28Z


 FAIL  src/Tabulators/MethodOfEqualShares.test.ts
  Method of Equal Shares Tests
    ✓ Basic Example (3 ms)
    ✓ Basic Example 2
    ✕ Basic Example 3 (3 ms)
    ✓ Influence Budget Redistribution
    ✓ Random Tiebreaker (1 ms)
    ✓ Random Tiebreaker with Defined Order (1 ms)
    ✓ Valid/Invalid/Under/Bullet Vote Counts (1 ms)

  ● Method of Equal Shares Tests › Basic Example 3

    expect(received).toBe(expected) // Object.is equality

    Expected: "Grace"
    Received: "Frank"

      81 |     expect(results.elected[0].name).toBe("Allison");
      82 |     expect(results.elected[1].name).toBe("Bill");
    > 83 |     expect(results.elected[2].name).toBe("Grace");
         |                                     ^
      84 |     expect(results.elected[3].name).toBe("Jack");
      85 |     expect(results.elected[4].name).toBe("Mona");
      86 |     expect(results.elected[5].name).toBe("Oscar");

      at Object.<anonymous> (src/Tabulators/MethodOfEqualShares.test.ts:83:37)

Test Suites: 1 failed, 1 total
Tests:       1 failed, 6 passed, 7 total
Snapshots:   0 total
Time:        2.183 s, estimated 3 s

Not sure why this is failing...

 {
      candidates: [
        { index: 0, name: 'Allison', tieBreakOrder: 0 },
        { index: 1, name: 'Bill', tieBreakOrder: 1 },
        { index: 2, name: 'Carmen', tieBreakOrder: 2 },
        { index: 3, name: 'Doug', tieBreakOrder: 3 },
        { index: 4, name: 'Eve', tieBreakOrder: 4 },
        { index: 5, name: 'Frank', tieBreakOrder: 5 },
        { index: 6, name: 'Grace', tieBreakOrder: 6 },
        { index: 7, name: 'Hank', tieBreakOrder: 7 },
        { index: 8, name: 'Ivy', tieBreakOrder: 8 },
        { index: 9, name: 'Jack', tieBreakOrder: 9 },
        { index: 10, name: 'Karen', tieBreakOrder: 10 },
        { index: 11, name: 'Leo', tieBreakOrder: 11 },
        { index: 12, name: 'Mona', tieBreakOrder: 12 },
        { index: 13, name: 'Nina', tieBreakOrder: 13 },
        { index: 14, name: 'Oscar', tieBreakOrder: 14 },
        { index: 15, name: 'Paul', tieBreakOrder: 15 },
        { index: 16, name: 'Quinn', tieBreakOrder: 16 },
        { index: 17, name: 'Rita', tieBreakOrder: 17 },
        { index: 18, name: 'Sam', tieBreakOrder: 18 }
      ],
      totalScores: [
        { index: 0, score: 6 },
        { index: 1, score: 6 },
        { index: 2, score: 4 },
        { index: 3, score: 5 },
        { index: 4, score: 5 },
        { index: 5, score: 6 },
        { index: 6, score: 7 },
        { index: 7, score: 5 },
        { index: 8, score: 5 },
        { index: 9, score: 6 },
        { index: 10, score: 2 },
        { index: 11, score: 5 },
        { index: 12, score: 6 },
        { index: 13, score: 4 },
        { index: 14, score: 6 },
        { index: 15, score: 3 },
        { index: 16, score: NaN },
        { index: 17, score: NaN },
        { index: 18, score: NaN }
      ],
      nValidVotes: 10,
      nInvalidVotes: 0,
      nUnderVotes: 0,
      nBulletVotes: 0
    }

@fsargent does this tool output any intermediate data that we can use to debug?

mikefranze · 2024-07-19T21:45:53Z

Could also check the box to use fractions instead of floats and check if we're hitting any tiebreaker scenarios.

mikefranze · 2024-07-20T07:48:53Z

Looks like a ties issue. In the tool you can click on the results at the bottom and get logs that includes a list of tied winner sets.

Your winners were: 0, 1, 5, 6, 9, 12

Tied winner sets:
0,1,5,6,12,14
0,1,6,9,12,14
0,1,5,6,8,12
0,1,5,6,9,12 <===
0,1,5,6,9,14
0,5,6,8,12,14
0,5,6,9,12,14
0,5,6,8,9,12
1,5,6,9,12,14

mikefranze · 2024-07-24T22:24:40Z

packages/backend/src/Tabulators/MethodOfEqualShares.ts

+function shuffle<T>(array: T[]): T[] {
+  const shuffled = array.slice();
+  for (let i = shuffled.length - 1; i > 0; i--) {
+    const j = Math.floor(Math.random() * (i + 1));


We shouldn't need a random generator here. The "randomTiebreakOrder" input to the main function is intended to determine how "random" ties are broken. This allows tests to be determinate and the server can generate a random order based on candidate UUIDs. Sorry that this wasn't documented.

@mikefranze Yeah, makes sense. I'm having issues because the existing tool (https://pref.tools/abcvoting/) doesn't actually describe what order the candidates are elected, so it's hard for me to write tests without me just 'guessing' who should win, or trusting my possibly faulty code.

fsargent added 2 commits July 13, 2024 21:41

Initial commit of MES

713fcf9

fsargent force-pushed the feat_add_MethodOfEqualShares branch 2 times, most recently from 6ce75b7 to 7f5a499 Compare July 18, 2024 17:26

Update ITabulators

512e788

fsargent force-pushed the feat_add_MethodOfEqualShares branch from 7f5a499 to 512e788 Compare July 18, 2024 17:28

Adding more tests.

484ba7c

fsargent force-pushed the feat_add_MethodOfEqualShares branch from 6ecc82e to 484ba7c Compare July 24, 2024 20:37

mikefranze reviewed Jul 24, 2024

View reviewed changes

Merge branch 'main' into feat_add_MethodOfEqualShares

cc70ba8

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feat: Add Method of Equal Shares #599

feat: Add Method of Equal Shares #599

fsargent commented Jul 14, 2024

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