org.apache.sysds.runtime.compress.colgroup.offset

Class OffsetFactory

java.lang.Object

org.apache.sysds.runtime.compress.colgroup.offset.OffsetFactory

public final class OffsetFactory
extends Object

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	OffsetFactory.OFF_TYPE

Constructor Summary

Constructors

Constructor and Description
OffsetFactory()

Method Summary

Modifier and Type	Method and Description
static AOffset	create(int[] indexes) Main factory pattern creator for Offsets.
static AOffset	create(int[] indexes, int apos, int alen) Create a Offset based on a subset of the indexes given.
static long	estimateInMemorySize(int size, int nRows) Avg diff only works assuming a normal distribution of the offsets.
static AOffset	readIn(DataInput in) Read in AOffset from the DataInput.

Methods inherited from class java.lang.Object

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

Constructor Detail

OffsetFactory

public OffsetFactory()

Method Detail

create

public static AOffset create(int[] indexes)

Main factory pattern creator for Offsets.

Parameters:

indexes - List of indexes, that is assumed to be sorted and have no duplicates

Returns:

AOffset object containing offsets to the next value.

create

public static AOffset create(int[] indexes,
                             int apos,
                             int alen)

Create a Offset based on a subset of the indexes given. This is useful if the input is created from a CSR matrix, since it allows us to not reallocate the indexes[] but use the shared indexes from the entire CSR representation.

Parameters:

indexes - The indexes from which to take the offsets

apos - The position to start looking from in the indexes

alen - The position to end looking at in the indexes.

Returns:

A new Offset.

readIn

public static AOffset readIn(DataInput in)
                      throws IOException

Read in AOffset from the DataInput.

Parameters:

in - DataInput to read from

Returns:

The AOffset data instance

Throws:

IOException - If the DataInput fails reading in the variables

estimateInMemorySize

public static long estimateInMemorySize(int size,
                                        int nRows)

Avg diff only works assuming a normal distribution of the offsets. This means that if we have 1000 rows and 100 offsets, it is assumed that on average the distance between elements is 10. Optionally todo is to add some number of size if the average distance is almost the same as the max value of the OffsetLists. this would add to the estimated size and approximate better the real compression size. It would also then handle edge cases better.

Parameters:

size - The estimated number of offsets

nRows - The number of rows.

Returns:

The estimated size of an offset given the number of offsets and rows.