mirror of
https://github.com/rui314/mold.git
synced 2024-09-11 21:17:28 +03:00
21 lines
442 B
C++
21 lines
442 B
C++
// This file implements HyperLogLog algorithm, which estimates
|
|
// the number of unique items in a given multiset.
|
|
//
|
|
// For more info, read
|
|
// https://engineering.fb.com/2018/12/13/data-infrastructure/hyperloglog
|
|
|
|
#include "mold.h"
|
|
|
|
#include <cmath>
|
|
|
|
namespace mold {
|
|
|
|
i64 HyperLogLog::get_cardinality() const {
|
|
double z = 0;
|
|
for (i64 val : buckets)
|
|
z += pow(2, -val);
|
|
return ALPHA * NBUCKETS * NBUCKETS / z;
|
|
}
|
|
|
|
} // namespace mold
|