sclass G22FindSimilarMasksTask<A> {

  // Image we are looking up

  settable Image2B queryImage;

  // optional - which primary mask holder is tasked with the search

  settable IG22MasksHolder maskSet;

  // where the found masks go (probability = similarity)

  settable new ProbabilisticList<FoundMask> outList;

  // probabilistic stack & scheduler

  settable new PStack pstack;

  // how many full mask comparisons were made

  int comparisons;

  // We all know what this is for

  settable bool verbose;

  // Has the search been ended?

  settable bool ended;

  class FoundMask {

    settable IG22Mask<A> mask;

    settable double similarity; // zero to one

    settable int candidateNumber;

    settable long stepCount;

    settable double foundAtProbability;

    Image2B image() { ret mask.image(); }

    A label() { ret mask.label(); }

    toString {

      ret renderVars("FoundMask",

        +label(),

        similarity := formatPercent(similarity),

        +candidateNumber);

    }

  }

  *() {}

  *(IG22Mask<A> mask) { queryImage(mask.image()); }

  *(Image2B image) { queryImage(image); }

  *(IImageRegion region, IG22MasksHolder *maskSet) {

    queryImage(maskSet.regionToMaskImage(region));

  }

  IProbabilisticScheduler scheduler() { ret pstack.scheduler(); }

  void tryMask(IG22Mask<A> candidate) {

    if (candidate == null) ret;

    comparisons++;

    var candidateImage = candidate.image();

    long diff = binaryImagePixelDifference_sameSize(queryImage, candidateImage);

    double p = liftProbabilityOffGround(1-doubleRatio(diff, area(candidateImage)));

    if (verbose)

      printVars("Candidate tested", +diff, +p, +candidate);

    foundMask(candidate, p);

  }

  void foundMask(IG22Mask<A> mask, double similarity) {

    long stepCount = scheduler().stepCount();

    if (verbose)

      print("Found mask with similarity " + formatDouble3X(similarity) + " in step " + stepCount);

    outList.at(similarity,

      new FoundMask().

        // actual result

        +mask.+similarity

        // stats to test effectivity of search heuristic

        .candidateNumber(comparisons).+stepCount

        .foundAtProbability(scheduler().currentProbability()));

  }

  void endSearch { ended(true); }

  // one-stop function

  ProbabilisticList<FoundMask> get(IG22MasksHolder maskSet default maskSet) {

    pstack.run(maskSet.findSimilarMasks(this));

    ret outList;

  }

}