# Package org.apache.sysds.runtime.compress.colgroup

- Class Summary
  Class | Description
  --- | ---
  AColGroup | Abstract Class that is the lowest class type for the Compression framework.
  AColGroupCompressed | Base class for column groups encoded Encoded in a compressed manner.
  AColGroupOffset | Base class for column groups encoded with various types of bitmap encoding.
  AColGroupValue | Base class for column groups encoded with value dictionary.
  AMorphingMMColGroup | Abstract class for column group types that do not perform matrix Multiplication, and decompression for performance reasons but instead transforms into another type of column group type to perform that operation.
  APreAgg | Abstract class for all the column groups that use preAggregation for Left matrix multiplications.
  ASDCZero |
  ColGroupConst |
  ColGroupDDC | Class to encapsulate information about a column group that is encoded with dense dictionary encoding (DDC).
  ColGroupDDCFOR | Class to encapsulate information about a column group that is encoded with dense dictionary encoding (DDC).
  ColGroupDeltaDDC | Class to encapsulate information about a column group that is first delta encoded then encoded with dense dictionary encoding (DeltaDDC).
  ColGroupEmpty |
  ColGroupFactory | Factory class for constructing ColGroups.
  ColGroupIO | This has the IO responsibility of ColGroups, such that it enables to read and write ColGroups to and from a DataInput and DataOutput
  ColGroupOLE | Class to encapsulate information about a column group that is encoded with simple lists of offsets for each set of distinct values.
  ColGroupRLE | A group of columns compressed with a single run-length encoded bitmap.
  ColGroupSDC | Column group that sparsely encodes the dictionary values.
  ColGroupSDCFOR | ColGroup for Patched Frame Of Reference.
  ColGroupSDCSingle | Column group that sparsely encodes the dictionary values.
  ColGroupSDCSingleZeros | Column group that sparsely encodes the dictionary values.
  ColGroupSDCZeros | Column group that sparsely encodes the dictionary values.
  ColGroupSizes |
  ColGroupUncompressed | Column group type for columns that are stored as dense arrays of doubles.
  ColGroupUtils |
  FORUtil |

- Enum Summary
  Enum | Description
  --- | ---
  AColGroup.CompressionType | Public super types of compression ColGroups supported