histogram.cpp

#include "partitioner.h"

void calcHist(relation& r, size_t start, size_t end, Histogram*& res,
              int64_t bits) {
  Histogram* _res = new Histogram{1 << bits};
  // histogram with as many partitions as threads
  for (size_t t = start; t < end; t++) {
    tuple record = r[t];
    int64_t index = Partitioner::hash1(record.getKey(), bits);
    (*_res)[index]++;
  }

  res = _res;
}

// create histogram with 2^n entries -- zero initialize all}
Histogram::Histogram(int64_t size)
    : entries{new int64_t[size]{}}, psum{new int64_t[size]{}}, size{size} {}

// increase value for a hashvalue
int64_t& Histogram::operator[](int64_t index) { return entries[index]; }

const int64_t* Histogram::generatePsum() {
  psum[0] = 0;

  for (int64_t p = 1; p < size; p++) psum[p] = psum[p - 1] + entries[p - 1];

  return psum;
}

int64_t Histogram::getPartitionPsum(int64_t index) const { return psum[index]; }

int64_t Histogram::getSize() const { return size; }

Histogram::~Histogram() {
  delete[] entries;
  delete[] psum;
}