view dbaccumulator.h @ 693:b1723ae7675e

begin work on sampling API

This is motivated by the need to be able to sample with arbitrary feature data
(e.g. from a feature file) against a database, for the JNMR "collections" paper
revisions or possible ISMIR paper revisions.  That bit doesn't work yet, but
the C-ified version of the current functionality (sample db x db and
sample key x db) works to the level of anecdotal tests.

The general approach is to mirror the _query_spec() API, where a whole heap
of knobs and twiddles are available to the user.  Unlike in the _query_spec()
API, not quite all of the knobs make sense (and even fewer are actually
implemented), but the basic idea is the same.

I pity the poor chump who will have to document all this.

template <class T> class DBAccumulator : public Accumulator {
public:
  DBAccumulator(unsigned int pointNN);
  ~DBAccumulator();
  void add_point(adb_result_t *r);
  adb_query_results_t *get_points();
private:
  unsigned int pointNN;
  std::priority_queue< adb_result_t, std::vector<adb_result_t>, T > *queue;
};

template <class T> DBAccumulator<T>::DBAccumulator(unsigned int pointNN)
  : pointNN(pointNN), queue(0) {
  queue = new std::priority_queue< adb_result_t, std::vector<adb_result_t>, T>;
}

template <class T> DBAccumulator<T>::~DBAccumulator() {
  if(queue) {
    delete queue;
  }
}

template <class T> void DBAccumulator<T>::add_point(adb_result_t *r) {
  if(!isnan(r->dist)) {
    queue->push(*r);
    if(queue->size() > pointNN) {
      queue->pop();
    }
  }
}

template <class T> adb_query_results_t *DBAccumulator<T>::get_points() {
  unsigned int size = queue->size();
  adb_query_results_t *r = (adb_query_results_t *) malloc(sizeof(adb_query_results_t));
  adb_result_t *rs = (adb_result_t *) calloc(size, sizeof(adb_result_t));
  r->nresults = size;
  r->results = rs;

  for(unsigned int k = 0; k < size; k++) {
    rs[k] = queue->top();
    queue->pop();
  }
  return r;
}