org.apache.sysds.runtime.matrix.data

## Class LibMatrixCountDistinct

- java.lang.Object
- - org.apache.sysds.runtime.matrix.data.LibMatrixCountDistinct

-     public class LibMatrixCountDistinct
      extends Object

  This class contains various methods for counting the number of distinct values inside a MatrixBlock

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static int` | `minimumSize` The minimum number NonZero of cells in the input before using approximate techniques for counting number of distinct values.

  - ### Method Summary

    All Methods Static Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `static int` | `estimateDistinctValues(MatrixBlock in, CountDistinctOperator op)` Public method to count the number of distinct values inside a matrix.

    - ### Methods inherited from class java.lang.Object

      `equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Field Detail

    - #### minimumSize

          public static int minimumSize

      The minimum number NonZero of cells in the input before using approximate techniques for counting number of distinct values.

  - ### Method Detail

    - #### estimateDistinctValues

          public static int estimateDistinctValues(MatrixBlock in,
                                                   CountDistinctOperator op)

      Public method to count the number of distinct values inside a matrix. Depending on which CountDistinctOperator selected it either gets the absolute number or a estimated value. TODO: Support counting num distinct in rows, or columns axis. TODO: Add support for distributed spark operations TODO: If the MatrixBlock type is CompressedMatrix, simply read the vaules from the ColGroups.
      Parameters:
        `in` - the input matrix to count number distinct values in
        `op` - the selected operator to use
      Returns:
        the distinct count

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