tree b193850a9fa2b42524d3dabf08e215d308db496b
parent 719ebe0d215035c054c435a5b7d790e643ec0fe1
author Sebastian <baunsgaard@tugraz.at> 1591128454 +0200
committer Matthias Boehm <mboehm7@gmail.com> 1591131160 +0200

[SYSTEMDS-396] Distinct values count/estimation functions

New function for counting the number of distinct values in a
MatrixBlock. It is using the builtin AggregateInstructions to parse
through hop lop. It can be called to execute with different types of
estimators:

- count : The default implementation that counts by adding to an
hashmap.
  Not memory efficient, but returns exact counts.
- KMV : An estimation algorithm K Minimum Values
- HLL : An estimation algorithm Hyper Log Log (Not finished)

Closes #909.