Sketch (datasketches-java 1.2.0-incubating API)

java.lang.Object
- org.apache.datasketches.theta.Sketch

Direct Known Subclasses:

CompactSketch, UpdateSketch
```
public abstract class Sketch
extends Object
```
The top-level class for all sketches. This class is never constructed directly. Use the UpdateSketch.builder() methods to create UpdateSketches.

Author:

Lee Rhodes

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method and Description
`abstract CompactSketch`	`compact()` Converts this sketch to an ordered CompactSketch on the Java heap.
`abstract CompactSketch`	`compact(boolean dstOrdered, org.apache.datasketches.memory.WritableMemory dstMem)` Convert this sketch to a CompactSketch in the chosen form.
`int`	`getCountLessThanTheta(double theta)` Gets the number of hash values less than the given theta.
`abstract int`	`getCurrentBytes(boolean compact)` Returns the number of storage bytes required for this Sketch in its current state.
`double`	`getEstimate()` Gets the unique count estimate.
`abstract Family`	`getFamily()` Returns the Family that this sketch belongs to
`double`	`getLowerBound(int numStdDev)` Gets the approximate lower error bound given the specified number of Standard Deviations.
`static int`	`getMaxCompactSketchBytes(int numberOfEntries)` Returns the maximum number of storage bytes required for a CompactSketch with the given number of actual entries.
`static int`	`getMaxUpdateSketchBytes(int nomEntries)` Returns the maximum number of storage bytes required for an UpdateSketch with the given number of nominal entries (power of 2).
`int`	`getRetainedEntries()` Returns the number of valid entries that have been retained by the sketch.
`abstract int`	`getRetainedEntries(boolean valid)` Returns the number of entries that have been retained by the sketch.
`static int`	`getSerializationVersion(org.apache.datasketches.memory.Memory mem)` Returns the serialization version from the given Memory
`double`	`getTheta()` Gets the value of theta as a double with a value between zero and one
`abstract long`	`getThetaLong()` Gets the value of theta as a long
`double`	`getUpperBound(int numStdDev)` Gets the approximate upper error bound given the specified number of Standard Deviations.
`abstract boolean`	`hasMemory()` Returns true if this sketch's data structure is backed by Memory or WritableMemory.
`static Sketch`	`heapify(org.apache.datasketches.memory.Memory srcMem)` Heapify takes the sketch image in Memory and instantiates an on-heap Sketch using the Default Update Seed.
`static Sketch`	`heapify(org.apache.datasketches.memory.Memory srcMem, long seed)` Heapify takes the sketch image in Memory and instantiates an on-heap Sketch using the given seed.
`abstract boolean`	`isCompact()` Returns true if this sketch is in compact form.
`abstract boolean`	`isDirect()` Returns true if the this sketch's internal data structure is backed by direct (off-heap) Memory.
`abstract boolean`	`isEmpty()` See Empty
`boolean`	`isEstimationMode()` Returns true if the sketch is Estimation Mode (as opposed to Exact Mode).
`abstract boolean`	`isOrdered()` Returns true if internal cache is ordered
`boolean`	`isSameResource(org.apache.datasketches.memory.Memory that)` Returns true if the backing resource of this is identical with the backing resource of that.
`abstract HashIterator`	`iterator()` Returns a HashIterator that can be used to iterate over the retained hash values of the Theta sketch.
`abstract byte[]`	`toByteArray()` Serialize this sketch to a byte array form.
`String`	`toString()` Returns a human readable summary of the sketch.
`String`	`toString(boolean sketchSummary, boolean dataDetail, int width, boolean hexMode)` Gets a human readable listing of contents and summary of the given sketch.
`static String`	`toString(byte[] byteArr)` Returns a human readable string of the preamble of a byte array image of a Theta Sketch.
`static String`	`toString(org.apache.datasketches.memory.Memory mem)` Returns a human readable string of the preamble of a Memory image of a Theta Sketch.
`static Sketch`	`wrap(org.apache.datasketches.memory.Memory srcMem)` Wrap takes the sketch image in Memory and refers to it directly.
`static Sketch`	`wrap(org.apache.datasketches.memory.Memory srcMem, long seed)` Wrap takes the sketch image in Memory and refers to it directly.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Method Detail
  - heapify
```
public static Sketch heapify(org.apache.datasketches.memory.Memory srcMem)
```
    Heapify takes the sketch image in Memory and instantiates an on-heap Sketch using the Default Update Seed. The resulting sketch will not retain any link to the source Memory.
    
    Parameters:
    
    srcMem - an image of a Sketch where the image seed hash matches the default seed hash. See Memory
    
    Returns:
    
    a Heap-based Sketch from the given Memory
  - heapify
```
public static Sketch heapify(org.apache.datasketches.memory.Memory srcMem,
                             long seed)
```
    Heapify takes the sketch image in Memory and instantiates an on-heap Sketch using the given seed. The resulting sketch will not retain any link to the source Memory.
    
    Parameters:
    
    srcMem - an image of a Sketch where the image seed hash matches the given seed hash. See Memory
    
    seed - See Update Hash Seed. Compact sketches store a 16-bit hash of the seed, but not the seed itself.
    
    Returns:
    
    a Heap-based Sketch from the given Memory
  - wrap
```
public static Sketch wrap(org.apache.datasketches.memory.Memory srcMem)
```
    Wrap takes the sketch image in Memory and refers to it directly. There is no data copying onto the java heap. Only "Direct" Serialization Version 3 (i.e, OpenSource) sketches that have been explicitly stored as direct objects can be wrapped. This method assumes the Util.DEFAULT_UPDATE_SEED. Default Update Seed.
    
    Parameters:
    
    srcMem - an image of a Sketch where the image seed hash matches the default seed hash. See Memory
    
    Returns:
    
    a Sketch backed by the given Memory
  - wrap
```
public static Sketch wrap(org.apache.datasketches.memory.Memory srcMem,
                          long seed)
```
    Wrap takes the sketch image in Memory and refers to it directly. There is no data copying onto the java heap. Only "Direct" Serialization Version 3 (i.e, OpenSource) sketches that have been explicitly stored as direct objects can be wrapped. An attempt to "wrap" earlier version sketches will result in a "heapified", normal Java Heap version of the sketch where all data will be copied to the heap.
    
    Parameters:
    
    srcMem - an image of a Sketch where the image seed hash matches the given seed hash. See Memory
    
    seed - See Update Hash Seed. Compact sketches store a 16-bit hash of the seed, but not the seed itself.
    
    Returns:
    
    a UpdateSketch backed by the given Memory
  - compact
```
public abstract CompactSketch compact()
```
    Converts this sketch to an ordered CompactSketch on the Java heap.
    If this sketch is already in compact form this operation returns this.
    
    Returns:
    
    this sketch as an ordered CompactSketch on the Java heap.
  - compact
```
public abstract CompactSketch compact(boolean dstOrdered,
                                      org.apache.datasketches.memory.WritableMemory dstMem)
```
    Convert this sketch to a CompactSketch in the chosen form.
    If this sketch is already in compact form this operation returns this.
    Otherwise, this compacting process converts the hash table form of an UpdateSketch to a simple list of the valid hash values from the hash table. Any hash values equal to or greater than theta will be discarded. The number of valid values remaining in the Compact Sketch depends on a number of factors, but may be larger or smaller than Nominal Entries (or k). It will never exceed 2k. If it is critical to always limit the size to no more than k, then rebuild() should be called on the UpdateSketch prior to this.
    
    Parameters:
    
    dstOrdered - See Destination Ordered
    
    dstMem - See Destination Memory.
    
    Returns:
    
    this sketch as a CompactSketch in the chosen form
  - getCountLessThanTheta
```
public int getCountLessThanTheta(double theta)
```
    Gets the number of hash values less than the given theta.
    
    Parameters:
    
    theta - the given theta as a double between zero and one.
    
    Returns:
    
    the number of hash values less than the given theta.
  - getCurrentBytes
```
public abstract int getCurrentBytes(boolean compact)
```
    Returns the number of storage bytes required for this Sketch in its current state.
    
    Parameters:
    
    compact - if true, returns the bytes required for compact form. If this sketch is already in compact form this parameter is ignored.
    
    Returns:
    
    the number of storage bytes required for this sketch
  - getEstimate
```
public double getEstimate()
```
    Gets the unique count estimate.
    
    Returns:
    
    the sketch's best estimate of the cardinality of the input stream.
  - getFamily
```
public abstract Family getFamily()
```
    Returns the Family that this sketch belongs to
    
    Returns:
    
    the Family that this sketch belongs to
  - iterator
```
public abstract HashIterator iterator()
```
    Returns a HashIterator that can be used to iterate over the retained hash values of the Theta sketch.
    
    Returns:
    
    a HashIterator that can be used to iterate over the retained hash values of the Theta sketch.
  - getLowerBound
```
public double getLowerBound(int numStdDev)
```
    Gets the approximate lower error bound given the specified number of Standard Deviations. This will return getEstimate() if isEmpty() is true.
    
    Parameters:
    
    numStdDev - See Number of Standard Deviations
    
    Returns:
    
    the lower bound.
  - getMaxCompactSketchBytes
```
public static int getMaxCompactSketchBytes(int numberOfEntries)
```
    Returns the maximum number of storage bytes required for a CompactSketch with the given number of actual entries. Note that this assumes the worse case of the sketch in estimation mode, which requires storing theta and count.
    
    Parameters:
    
    numberOfEntries - the actual number of entries stored with the CompactSketch.
    
    Returns:
    
    the maximum number of storage bytes required for a CompactSketch with the given number of entries.
  - getMaxUpdateSketchBytes
```
public static int getMaxUpdateSketchBytes(int nomEntries)
```
    Returns the maximum number of storage bytes required for an UpdateSketch with the given number of nominal entries (power of 2).
    
    Parameters:
    
    nomEntries - Nominal Entres This will become the ceiling power of 2 if it is not.
    
    Returns:
    
    the maximum number of storage bytes required for a UpdateSketch with the given nomEntries
  - getRetainedEntries
```
public int getRetainedEntries()
```
    Returns the number of valid entries that have been retained by the sketch.
    
    Returns:
    
    the number of valid retained entries
  - getRetainedEntries
```
public abstract int getRetainedEntries(boolean valid)
```
    Returns the number of entries that have been retained by the sketch.
    
    Parameters:
    
    valid - if true, returns the number of valid entries, which are less than theta and used for estimation. Otherwise, return the number of all entries, valid or not, that are currently in the internal sketch cache.
    
    Returns:
    
    the number of retained entries
  - getSerializationVersion
```
public static int getSerializationVersion(org.apache.datasketches.memory.Memory mem)
```
    Returns the serialization version from the given Memory
    
    Parameters:
    
    mem - the sketch Memory
    
    Returns:
    
    the serialization version from the Memory
  - getTheta
```
public double getTheta()
```
    Gets the value of theta as a double with a value between zero and one
    
    Returns:
    
    the value of theta as a double
  - getThetaLong
```
public abstract long getThetaLong()
```
    Gets the value of theta as a long
    
    Returns:
    
    the value of theta as a long
  - getUpperBound
```
public double getUpperBound(int numStdDev)
```
    Gets the approximate upper error bound given the specified number of Standard Deviations. This will return getEstimate() if isEmpty() is true.
    
    Parameters:
    
    numStdDev - See Number of Standard Deviations
    
    Returns:
    
    the upper bound.
  - hasMemory
```
public abstract boolean hasMemory()
```
    Returns true if this sketch's data structure is backed by Memory or WritableMemory.
    
    Returns:
    
    true if this sketch's data structure is backed by Memory or WritableMemory.
  - isCompact
```
public abstract boolean isCompact()
```
    Returns true if this sketch is in compact form.
    
    Returns:
    
    true if this sketch is in compact form.
  - isDirect
```
public abstract boolean isDirect()
```
    Returns true if the this sketch's internal data structure is backed by direct (off-heap) Memory.
    
    Returns:
    
    true if the this sketch's internal data structure is backed by direct (off-heap) Memory.
  - isEmpty
```
public abstract boolean isEmpty()
```
    See Empty
    
    Returns:
    
    true if empty.
  - isEstimationMode
```
public boolean isEstimationMode()
```
    Returns true if the sketch is Estimation Mode (as opposed to Exact Mode). This is true if theta < 1.0 AND isEmpty() is false.
    
    Returns:
    
    true if the sketch is in estimation mode.
  - isOrdered
```
public abstract boolean isOrdered()
```
    Returns true if internal cache is ordered
    
    Returns:
    
    true if internal cache is ordered
  - isSameResource
```
public boolean isSameResource(org.apache.datasketches.memory.Memory that)
```
    Returns true if the backing resource of this is identical with the backing resource of that. The capacities must be the same. If this is a region, the region offset must also be the same.
    
    Parameters:
    
    that - A different non-null object
    
    Returns:
    
    true if the backing resource of this is the same as the backing resource of that.
  - toByteArray
```
public abstract byte[] toByteArray()
```
    Serialize this sketch to a byte array form.
    
    Returns:
    
    byte array of this sketch
  - toString
```
public String toString()
```
    Returns a human readable summary of the sketch. This method is equivalent to the parameterized call:
    Sketch.toString(sketch, true, false, 8, true);
    
    Overrides:
    
    toString in class Object
    
    Returns:
    
    summary
  - toString
```
public String toString(boolean sketchSummary,
                       boolean dataDetail,
                       int width,
                       boolean hexMode)
```
    Gets a human readable listing of contents and summary of the given sketch. This can be a very long string. If this sketch is in a "dirty" state there may be values in the dataDetail view that are ≥ theta.
    
    Parameters:
    
    sketchSummary - If true the sketch summary will be output at the end.
    
    dataDetail - If true, includes all valid hash values in the sketch.
    
    width - The number of columns of hash values. Default is 8.
    
    hexMode - If true, hashes will be output in hex.
    
    Returns:
    
    The result string, which can be very long.
  - toString
```
public static String toString(byte[] byteArr)
```
    Returns a human readable string of the preamble of a byte array image of a Theta Sketch.
    
    Parameters:
    
    byteArr - the given byte array
    
    Returns:
    
    a human readable string of the preamble of a byte array image of a Theta Sketch.
  - toString
```
public static String toString(org.apache.datasketches.memory.Memory mem)
```
    Returns a human readable string of the preamble of a Memory image of a Theta Sketch.
    
    Parameters:
    
    mem - the given Memory object
    
    Returns:
    
    a human readable string of the preamble of a Memory image of a Theta Sketch.

Class Sketch

Method Summary

Methods inherited from class java.lang.Object

Method Detail

heapify

heapify

wrap

wrap

compact

compact

getCountLessThanTheta

getCurrentBytes

getEstimate

getFamily

iterator

getLowerBound

getMaxCompactSketchBytes

getMaxUpdateSketchBytes

getRetainedEntries

getRetainedEntries

getSerializationVersion

getTheta

getThetaLong

getUpperBound

hasMemory

isCompact

isDirect

isEmpty

isEstimationMode

isOrdered

isSameResource

toByteArray

toString

toString

toString

toString