New system (#18)

* Set default rating to 1400.
* Add delta comparison utility.

Author: meooow25

README.md

@@ -11,7 +11,7 @@ Carrot runs in the browser and fetches all the data it needs from the [Codeforce
 It then calculates the rating changes following the algorithm published by Mike Mirzayanov [here](https://codeforces.com/blog/entry/20762), slightly modified so that it matches the current CF algorithm. This updated algorithm is adapted from [TLE](https://github.com/cheran-senthil/TLE/blob/master/tle/util/ranklist/rating_calculator.py).
 
 #### Is this better than [CF-Predictor](https://codeforces.com/blog/entry/50411)?
-Not necessarily. The CF-Predictor extension communicates with a server, while Carrot fetches data and performs all calculations in the browser. So the network usage is significantly lower for CF-Predictor. However, Carrot is 100% accurate and it works in real time.
+Not necessarily. The CF-Predictor extension communicates with a server, while Carrot fetches data and performs all calculations in the browser. So the network usage is significantly lower for CF-Predictor. However, Carrot is ~~100% accurate~~(see [#18](https://github.com/meooow25/carrot/pull/18)) and it works in real time.
 
 #### How is Carrot fast enough to calculate rating changes of every contestant in real time?
 FFT. The answer is always FFT.

carrot/src/background/predict-response.js

@@ -35,9 +35,9 @@ export default class PredictResponse {
           break;
         case PredictResponse.TYPE_FINAL:
           // For an unrated user, user info has missing rating but if the user participates, the
-          // oldRating on the ratingChange object is set as 1500. So, for FINAL, at the moment
-          // rating = effectiveRating always, but keeping the code which works for unrated too, as
-          // things should be.
+          // oldRating on the ratingChange object is set as the default starting value. So, for
+          // FINAL, at the moment rating = effectiveRating always, but keeping the code which works
+          // for unrated too, as things should be.
           rank = Rank.forRating(result.rating);
           newRank = Rank.forRating(result.effectiveRating + result.delta);
           break;

carrot/src/background/predict.js

@@ -10,7 +10,7 @@ import FFTConv from '../util/conv.js';
  */
 
 const PRINT_PERFORMANCE = false;
-const DEFAULT_RATING = 1500;
+const DEFAULT_RATING = 1400;
 
 export class Contestant {
   constructor(party, points, penalty, rating) {

carrot/tests/compare.ts

@@ -0,0 +1,66 @@
+import * as colors from 'https://deno.land/std/fmt/colors.ts';
+import * as api from '../src/background/cf-api.js';
+import predict, { Contestant } from '../src/background/predict.js';
+
+/**
+ * Compares actual vs calculated rating changes for a given finished rated contest.
+ * Matches upto Educational round 87 (1354). New rating system was imposed after that.
+ * 
+ * $ deno run --allow-net compare.ts <contest-id>
+ */
+
+async function main() {
+  const contestId = Deno.args[0];
+  if (!contestId || isNaN(parseInt(contestId))) {
+    console.error('Missing or bad contest ID');
+    return;
+  }
+
+  console.info('Contest ' + contestId);
+  console.info('Fetching rating changes...');
+  const ratingChanges = await api.contest.ratingChanges(contestId);
+  if (ratingChanges.length) {
+    console.log('  Fetched ' + ratingChanges.length + ' rating changes');
+  } else {
+    console.error('Empty rating change list');
+    return;
+  }
+
+  const rating = Object.fromEntries(
+    ratingChanges.map((r: any) => [r.handle, { old: r.oldRating, new: r.newRating }]));
+
+  console.info('Fetching standings...');
+  let { contest_, problems_, rows } = await api.contest.standings(contestId);
+  console.info('  Fetched ' + rows.length + ' rows');
+  rows = rows.filter((row: any) => row.party.members[0].handle in rating);
+  console.info('  ' + rows.length + ' rows retained from rating change list');
+
+  console.info('Calculating deltas...');
+  const contestants = rows.map((row: any) => {
+    const handle = row.party.members[0].handle;
+    return new Contestant(handle, row.points, row.penalty, rating[handle].old);
+  });
+  const predictResults = predict(contestants);
+
+  const diffs = [];
+  for (const res of predictResults) {
+    const actualDelta = rating[res.handle].new - rating[res.handle].old;
+    if (res.delta != actualDelta) {
+      diffs.push([res.handle, rating[res.handle].old, actualDelta, res.delta]);
+    }
+  }
+  if (diffs.length) {
+    console.error(colors.red(`Delta mismatch for ${diffs.length} contestants:`));
+    console.error(colors.red('[handle, old rating, actual delta, calculated delta]'));
+    for (const row of diffs.slice(0, 5)) {
+      console.error(colors.red('[' + row.join(', ') + ']'));
+    }
+    if (diffs.length > 5) {
+      console.log(colors.red(`...and ${diffs.length - 5} more`));
+    }
+  } else {
+    console.info(colors.green('OK all match'));
+  }
+}
+
+main();

carrot/tests/test-predict.ts

@@ -19,13 +19,13 @@ function predictedDeltas(data: TestDataRow[]): object {
 
 Deno.test('predict_ok', (): void => {
   const data: TestDataRow[] = [
-    ['bigbrain', 4000, 10, 3000, -237],
-    ['smartguy', 2500, 50, 2400, -175],
-    ['ordinaryguy', 1500, 80, 1800, -35],
-    ['brick', -100, 300, 500, -50],
-    ['alt', 5000, 0, undefined, 514],
-    ['luckyguy', 2500, 40, 1800, 121],
-    ['unluckyguy', 800, 40, 2000, -145],
+    ['bigbrain', 4000, 10, 3000, -241],
+    ['smartguy', 2500, 50, 2400, -181],
+    ['ordinaryguy', 1500, 80, 1800, -48],
+    ['brick', -100, 300, 500, -54],
+    ['alt', 5000, 0, undefined, 553],
+    ['luckyguy', 2500, 40, 1800, 118],
+    ['unluckyguy', 800, 40, 2000, -160],
   ];
 
   assertEquals(predictedDeltas(data), expectedDeltas(data));