uk.ac.starlink.table.join

Class BitsetMask

java.lang.Object

uk.ac.starlink.table.join.BitsetMask

All Implemented Interfaces:

HealpixMask

public class BitsetMask
extends Object
implements HealpixMask

HealpixMask implementation based on a BitSet representing all the pixels at a given HEALPix order.

This implementation is not very sophisticated (it doesn't attempt a multi-order representation), but it's fairly efficient as long as the order (resolution) required is modest. A value like 6 is probably reasonable; 49k pixels, 6kbyte storage.

Since:

8 Jun 2022

Author:

Mark Taylor

Nested Class Summary

Nested classes/interfaces inherited from interface uk.ac.starlink.table.join.HealpixMask

HealpixMask.PixelTester

Field Summary

Fields

Modifier and Type	Field and Description
static int	DEFAULT_ORDER Suitable HEALPix order for general use.

Constructor Summary

Constructors

Constructor and Description
BitsetMask() Constructs a new empty mask with the default order.
BitsetMask(int order) Constructs a new empty mask with a given order.

Method Summary

Modifier and Type	Method and Description
void	addPixel(int order, long ipix) Adds the area corresponding to a HEALPix pixel to this mask.
HealpixMask.PixelTester	createPixelTester() Returns an object that can test inclusion in the sky area defined by the current state of this mask.
int	getOrder() Returns the HEALPix order of the pixels stored by this mask.
int[]	getPixels() Returns an array of the pixels contained by this mask.
double	getSkyFraction() Returns the fraction of the sky currently covered by this mask.
void	intersection(HealpixMask other) Narrows this area to represent the intersection of this mask and another compatible mask.
boolean	isEmpty() Returns true if this mask's area is empty.
void	union(HealpixMask other) Extends this area to represent the union of this mask and another compatible mask.

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_ORDER

public static final int DEFAULT_ORDER

Suitable HEALPix order for general use.

See Also:

Constant Field Values

Constructor Detail

BitsetMask

public BitsetMask()

Constructs a new empty mask with the default order.

BitsetMask

public BitsetMask(int order)

Constructs a new empty mask with a given order.

Parameters:

order - HEALPix order

Method Detail

isEmpty

public boolean isEmpty()

Description copied from interface: HealpixMask

Returns true if this mask's area is empty.

Specified by:

isEmpty in interface HealpixMask

Returns:

true iff the HealpixMask.createPixelTester() test is guaranteed to return false

intersection

public void intersection(HealpixMask other)

Description copied from interface: HealpixMask

Narrows this area to represent the intersection of this mask and another compatible mask.

Specified by:

intersection in interface HealpixMask

Parameters:

other - different mask of a type assumed compatible with this one

union

public void union(HealpixMask other)

Description copied from interface: HealpixMask

Extends this area to represent the union of this mask and another compatible mask.

Specified by:

union in interface HealpixMask

Parameters:

other - different mask of a type assumed compatible with this one

getSkyFraction

public double getSkyFraction()

Description copied from interface: HealpixMask

Returns the fraction of the sky currently covered by this mask.

Specified by:

getSkyFraction in interface HealpixMask

Returns:

sky fraction between 0 and 1

addPixel

public void addPixel(int order,
                     long ipix)

Description copied from interface: HealpixMask

Adds the area corresponding to a HEALPix pixel to this mask.

Specified by:

addPixel in interface HealpixMask

Parameters:

order - HEALPix order

ipix - HEALPix pixel index at order order

createPixelTester

public HealpixMask.PixelTester createPixelTester()

Description copied from interface: HealpixMask

Returns an object that can test inclusion in the sky area defined by the current state of this mask.

Specified by:

createPixelTester in interface HealpixMask

Returns:

thread-safe test for sky area inclusion

getOrder

public int getOrder()

Returns the HEALPix order of the pixels stored by this mask.

Returns:

healpix order

getPixels

public int[] getPixels()

Returns an array of the pixels contained by this mask. This is mainly intended for diagnostic purposes, it may not be very efficient.

Returns:

pixel list at this mask's order