kaprekartestmultithread.js

const { Worker, isMainThread, parentPort, workerData } = require('worker_threads');
const os = require('os');

if (isMainThread) {
  // Main thread
  const NUM_WORKERS = os.cpus().length;
  const START = 100;
  const END = 100_000_000;
  const CHUNK_SIZE = Math.ceil((END - START) / NUM_WORKERS);

  const globalSeen = {};
  const globalReachedNums = new Set();
  let completedWorkers = 0;

  console.log(`Starting ${NUM_WORKERS} workers...`);
  console.log(`Range: ${START} to ${END}`);
  console.time('Total time');

  for (let i = 0; i < NUM_WORKERS; i++) {
    const rangeStart = START + i * CHUNK_SIZE;
    const rangeEnd = Math.min(rangeStart + CHUNK_SIZE, END);

    const worker = new Worker(__filename, {
      workerData: { rangeStart, rangeEnd, workerId: i + 1 }
    });

    worker.on('message', ({ seen, reachedNums, workerId }) => {
      console.log(`Worker ${workerId} completed`);

      // Merge results
      for (const [key, value] of Object.entries(seen)) {
        if (key in globalSeen) {
          globalSeen[key].push(...value);
        } else {
          globalSeen[key] = value;
        }
      }
      reachedNums.forEach(num => globalReachedNums.add(num));
    });

    worker.on('error', err => console.error(`Worker ${i + 1} error:`, err));

    worker.on('exit', () => {
      completedWorkers++;
      if (completedWorkers === NUM_WORKERS) {
        console.timeEnd('Total time');
        console.log('\nSeen:', globalSeen);
        console.log('\nReached Nums:', globalReachedNums);
      }
    });
  }

} else {
  // Worker thread
  const { rangeStart, rangeEnd, workerId } = workerData;

  const maxNum = num => +[...`${num}`].sort((a, b) => b - a).join('');
  const minNum = num => +[...`${num}`].sort((a, b) => a - b).join('');

  const reachedNums = new Set();
  const seen = {};
  const MAX_STEP = 1_000_000;

  const findKaprekar = (i, _min, _max, prev, step) => {
    let diff = _max - _min;
    while (diff) {
      if (step > MAX_STEP) {
        if (diff in seen) {
          console.log(`[Worker ${workerId}] found`, i, diff, prev, step);
        } else {
          seen[diff] = [-i];
        }
        break;
      }
      if (diff in seen) {
        break;
      }
      if (prev === diff) {
        seen[diff] = [i];
        reachedNums.add(prev);
        break;
      }
      prev = diff;
      diff = maxNum(diff) - minNum(diff);
      step++;
    }
  };

  console.log(`Worker ${workerId} processing range ${rangeStart} to ${rangeEnd}`);

  for (let i = rangeStart; i < rangeEnd; i++) {
    findKaprekar(i, minNum(i), maxNum(i), null, 1);
  }

  parentPort.postMessage({
    seen,
    reachedNums: [...reachedNums],
    workerId
  });
}