Code Coverage |
||||||||||
Lines |
Functions and Methods |
Classes and Traits |
||||||||
| Total | |
63.41% |
52 / 82 |
|
33.33% |
3 / 9 |
CRAP | |
0.00% |
0 / 1 |
| SchulzeTallier | |
63.41% |
52 / 82 |
|
33.33% |
3 / 9 |
74.07 | |
0.00% |
0 / 1 |
| getPathStrengths | |
75.00% |
24 / 32 |
|
0.00% |
0 / 1 |
15.64 | |||
| convertStrengthMatrixToRanks | |
95.24% |
20 / 21 |
|
0.00% |
0 / 1 |
8 | |||
| isSchulzeWin | |
100.00% |
1 / 1 |
|
100.00% |
1 / 1 |
3 | |||
| finishTally | |
100.00% |
2 / 2 |
|
100.00% |
1 / 1 |
1 | |||
| getRanks | |
0.00% |
0 / 1 |
|
0.00% |
0 / 1 |
2 | |||
| loadJSONResult | |
0.00% |
0 / 3 |
|
0.00% |
0 / 1 |
2 | |||
| getJSONResult | |
100.00% |
5 / 5 |
|
100.00% |
1 / 1 |
1 | |||
| getHtmlResult | |
0.00% |
0 / 8 |
|
0.00% |
0 / 1 |
2 | |||
| getTextResult | |
0.00% |
0 / 9 |
|
0.00% |
0 / 1 |
2 | |||
| 1 | <?php |
| 2 | |
| 3 | namespace MediaWiki\Extension\SecurePoll\Talliers; |
| 4 | |
| 5 | /** |
| 6 | * This is the basic Schulze method with no tie-breaking. The algorithm in this |
| 7 | * class is believed to be equivalent to the method in the Debian constitution, |
| 8 | * assuming no quorum and no default option. It has been cross-tested against |
| 9 | * debian-vote (but not devotee). |
| 10 | */ |
| 11 | class SchulzeTallier extends PairwiseTallier { |
| 12 | /** @var array|null */ |
| 13 | public $ranks; |
| 14 | /** @var array|null */ |
| 15 | public $strengths; |
| 16 | |
| 17 | /** |
| 18 | * @param array $victories |
| 19 | * @return array |
| 20 | */ |
| 21 | private function getPathStrengths( $victories ) { |
| 22 | # This algorithm follows Markus Schulze, "A New Monotonic, Clone-Independent, Reversal |
| 23 | # Symmetric, and Condorcet-Consistent Single-Winner Election Method" and also |
| 24 | # http://en.wikipedia.org/w/index.php?title=User:MarkusSchulze/Statutory_Rules&oldid=303036893 |
| 25 | # Path strengths in the Schulze method are given by pairs of integers notated (a, b) |
| 26 | # where a is the strength in one direction and b is the strength in the other. We make |
| 27 | # a matrix of path strength pairs "p", giving the path strength of the row index beating |
| 28 | # the column index. |
| 29 | |
| 30 | # First the path strength matrix is populated with the "direct" victory count in each |
| 31 | # direction, i.e. the number of people who preferenced A over B, and B over A. |
| 32 | $strengths = []; |
| 33 | foreach ( $this->optionIds as $oid1 ) { |
| 34 | foreach ( $this->optionIds as $oid2 ) { |
| 35 | if ( $oid1 === $oid2 ) { |
| 36 | continue; |
| 37 | } |
| 38 | $v12 = $victories[$oid1][$oid2]; |
| 39 | $v21 = $victories[$oid2][$oid1]; |
| 40 | if ( $v12 > $v21 ) { |
| 41 | # Direct victory |
| 42 | $strengths[$oid1][$oid2] = [ |
| 43 | $v12, |
| 44 | $v21 |
| 45 | ]; |
| 46 | } else { |
| 47 | # Direct loss |
| 48 | $strengths[$oid1][$oid2] = [ |
| 49 | 0, |
| 50 | 0 |
| 51 | ]; |
| 52 | } |
| 53 | } |
| 54 | } |
| 55 | |
| 56 | # Next (continuing the Floyd-Warshall algorithm) we calculate the strongest indirect |
| 57 | # paths. This part dominates the O(N^3) time order. |
| 58 | foreach ( $this->optionIds as $oid1 ) { |
| 59 | foreach ( $this->optionIds as $oid2 ) { |
| 60 | if ( $oid1 === $oid2 ) { |
| 61 | continue; |
| 62 | } |
| 63 | foreach ( $this->optionIds as $oid3 ) { |
| 64 | if ( $oid1 === $oid3 || $oid2 === $oid3 ) { |
| 65 | continue; |
| 66 | } |
| 67 | $s21 = $strengths[$oid2][$oid1]; |
| 68 | $s13 = $strengths[$oid1][$oid3]; |
| 69 | $s23 = $strengths[$oid2][$oid3]; |
| 70 | if ( $this->isSchulzeWin( $s21, $s13 ) ) { |
| 71 | $temp = $s13; |
| 72 | } else { |
| 73 | $temp = $s21; |
| 74 | } |
| 75 | if ( $this->isSchulzeWin( $temp, $s23 ) ) { |
| 76 | $strengths[$oid2][$oid3] = $temp; |
| 77 | } |
| 78 | } |
| 79 | } |
| 80 | } |
| 81 | |
| 82 | return $strengths; |
| 83 | } |
| 84 | |
| 85 | private function convertStrengthMatrixToRanks( $strengths ) { |
| 86 | $unusedIds = $this->optionIds; |
| 87 | $ranks = []; |
| 88 | $currentRank = 1; |
| 89 | |
| 90 | while ( count( $unusedIds ) ) { |
| 91 | $winners = array_flip( $unusedIds ); |
| 92 | foreach ( $unusedIds as $oid1 ) { |
| 93 | foreach ( $unusedIds as $oid2 ) { |
| 94 | if ( $oid1 == $oid2 ) { |
| 95 | continue; |
| 96 | } |
| 97 | $s12 = $strengths[$oid1][$oid2]; |
| 98 | $s21 = $strengths[$oid2][$oid1]; |
| 99 | if ( $this->isSchulzeWin( $s21, $s12 ) ) { |
| 100 | # oid1 is defeated by someone, not a winner |
| 101 | unset( $winners[$oid1] ); |
| 102 | break; |
| 103 | } |
| 104 | } |
| 105 | } |
| 106 | if ( !count( $winners ) ) { |
| 107 | # No winners, everyone ties for this position |
| 108 | $winners = array_flip( $unusedIds ); |
| 109 | } |
| 110 | |
| 111 | # Now $winners is the list of candidates that tie for this position |
| 112 | foreach ( $winners as $oid => $unused ) { |
| 113 | $ranks[$oid] = $currentRank; |
| 114 | } |
| 115 | $currentRank += count( $winners ); |
| 116 | $unusedIds = array_diff( $unusedIds, array_keys( $winners ) ); |
| 117 | } |
| 118 | |
| 119 | return $ranks; |
| 120 | } |
| 121 | |
| 122 | /** |
| 123 | * Determine whether Schulze's win relation "s1 >win s2" for path strength |
| 124 | * pairs s1 and s2 is satisfied. |
| 125 | * |
| 126 | * When applied to final path strengths instead of intermediate results, |
| 127 | * the paper notates this relation >D (greater than subscript D). |
| 128 | * |
| 129 | * The inequality in the second part is reversed because the first part |
| 130 | * refers to wins, and the second part refers to losses. |
| 131 | * @param array $s1 |
| 132 | * @param array $s2 |
| 133 | * @return bool |
| 134 | */ |
| 135 | private function isSchulzeWin( $s1, $s2 ) { |
| 136 | return $s1[0] > $s2[0] || ( $s1[0] == $s2[0] && $s1[1] < $s2[1] ); |
| 137 | } |
| 138 | |
| 139 | /** |
| 140 | * @inheritDoc |
| 141 | * |
| 142 | */ |
| 143 | public function finishTally() { |
| 144 | $this->strengths = $this->getPathStrengths( $this->victories ); |
| 145 | $this->ranks = $this->convertStrengthMatrixToRanks( $this->strengths ); |
| 146 | } |
| 147 | |
| 148 | public function getRanks() { |
| 149 | return $this->ranks; |
| 150 | } |
| 151 | |
| 152 | /** |
| 153 | * @inheritDoc |
| 154 | * |
| 155 | */ |
| 156 | public function loadJSONResult( $data ) { |
| 157 | $this->ranks = $data['ranks']; |
| 158 | $this->victories = $data['victories']; |
| 159 | $this->strengths = $data['strengths']; |
| 160 | } |
| 161 | |
| 162 | /** |
| 163 | * @inheritDoc |
| 164 | * |
| 165 | */ |
| 166 | public function getJSONResult() { |
| 167 | return [ |
| 168 | 'ranks' => $this->ranks, |
| 169 | 'victories' => $this->victories, |
| 170 | 'strengths' => $this->strengths, |
| 171 | ]; |
| 172 | } |
| 173 | |
| 174 | /** |
| 175 | * @inheritDoc |
| 176 | * |
| 177 | */ |
| 178 | public function getHtmlResult() { |
| 179 | $s = '<h2>' . wfMessage( 'securepoll-ranks' )->parse() . "</h2>\n"; |
| 180 | $s .= $this->convertRanksToHtml( $this->ranks ); |
| 181 | |
| 182 | $s .= '<h2>' . wfMessage( 'securepoll-pairwise-victories' )->parse() . "</h2>\n"; |
| 183 | $rankedIds = array_keys( $this->ranks ); |
| 184 | $s .= $this->convertMatrixToHtml( $this->victories, $rankedIds ); |
| 185 | |
| 186 | $s .= '<h2>' . wfMessage( 'securepoll-strength-matrix' )->parse() . "</h2>\n"; |
| 187 | $s .= $this->convertMatrixToHtml( $this->strengths, $rankedIds ); |
| 188 | |
| 189 | return $s; |
| 190 | } |
| 191 | |
| 192 | /** |
| 193 | * @inheritDoc |
| 194 | * |
| 195 | */ |
| 196 | public function getTextResult() { |
| 197 | $rankedIds = array_keys( $this->ranks ); |
| 198 | |
| 199 | return wfMessage( 'securepoll-ranks' )->text() . "\n" . $this->convertRanksToText( |
| 200 | $this->ranks |
| 201 | ) . "\n\n" . wfMessage( 'securepoll-pairwise-victories' )->text( |
| 202 | ) . "\n" . $this->convertMatrixToText( |
| 203 | $this->victories, |
| 204 | $rankedIds |
| 205 | ) . "\n\n" . wfMessage( 'securepoll-strength-matrix' )->text( |
| 206 | ) . "\n" . $this->convertMatrixToText( $this->strengths, $rankedIds ); |
| 207 | } |
| 208 | } |