Long computation

Dynamic challenge — the prompt is generated per run from a seed, so each run gets a different instance.

generate

(function(a){
  var s = (a.seed >>> 0) + 31337;
  function next(){
    s = (Math.imul(s, 22695477) + 1) >>> 0;
    return s;
  }
  function rotl32(x, r){
    return ((x << r) | (x >>> (32 - r))) >>> 0;
  }
  function hex32(x){
    return ("00000000" + (x >>> 0).toString(16)).slice(-8);
  }
  var data = [];
  for (var i = 0; i < 12; i++) {
    data.push(next() >>> 0);
  }
  var x0 = next() >>> 0;
  var y0 = next() >>> 0;
  var x = x0;
  var y = y0;
  var rounds = 25000;
  for (var step = 0; step < rounds; step++) {
    x = (Math.imul((x ^ data[step % data.length] ^ step) >>> 0, 2654435761) + rotl32(y, 5)) >>> 0;
    y = (Math.imul((y + data[(step + 7) % data.length] + step) >>> 0, 1597334677) ^ rotl32(x, 11)) >>> 0;
    x = (x + rotl32((y ^ step) >>> 0, 3)) >>> 0;
  }
  var expected = hex32(x) + "-" + hex32(y);
  return {
    prompt:
      "Write and run a short program to compute this exactly. Use unsigned 32-bit arithmetic modulo 2^32 throughout. " +
      "Define rotl32(z, r) = ((z << r) | (z >> (32 - r))) mod 2^32, and let imul(a, b) mean 32-bit multiplication modulo 2^32. " +
      "Start with data = [" + data.join(", ") + "], x = " + x0 + ", y = " + y0 + " and rounds = " + rounds + ". " +
      "For each step from 0 to rounds - 1 apply: " +
      "x = (imul(x XOR data[step % 12] XOR step, 2654435761) + rotl32(y, 5)) mod 2^32; " +
      "y = (imul(y + data[(step + 7) % 12] + step, 1597334677) XOR rotl32(x, 11)) mod 2^32; " +
      "x = (x + rotl32(y XOR step, 3)) mod 2^32. " +
      "Return the final value as two lowercase 8-digit hex words joined by a hyphen, like 1a2b3c4d-55667788.",
    expected: expected
  };
})

evaluate

(function(a){
  var answer = String(a.submission == null ? "" : a.submission).trim().toLowerCase();
  var expected = String(a.expected == null ? "" : a.expected).trim().toLowerCase();
  var pass = answer === expected;
  return { pass: pass, score: pass ? 1 : 0 };
})

submissions (0)