org.HdrHistogram
Class Histogram

java.lang.Object
  org.HdrHistogram.EncodableHistogram
      org.HdrHistogram.AbstractHistogram
          org.HdrHistogram.Histogram

All Implemented Interfaces:

Serializable

Direct Known Subclasses:

AtomicHistogram, ConcurrentHistogram, SynchronizedHistogram

public class Histogram
extends AbstractHistogram

A High Dynamic Range (HDR) Histogram

Histogram supports the recording and analyzing sampled data value counts across a configurable integer value range with configurable value precision within the range. Value precision is expressed as the number of significant digits in the value recording, and provides control over value quantization behavior across the value range and the subsequent value resolution at any given level.

For example, a Histogram could be configured to track the counts of observed integer values between 0 and 3,600,000,000 while maintaining a value precision of 3 significant digits across that range. Value quantization within the range will thus be no larger than 1/1,000th (or 0.1%) of any value. This example Histogram could be used to track and analyze the counts of observed response times ranging between 1 microsecond and 1 hour in magnitude, while maintaining a value resolution of 1 microsecond up to 1 millisecond, a resolution of 1 millisecond (or better) up to one second, and a resolution of 1 second (or better) up to 1,000 seconds. At its maximum tracked value (1 hour), it would still maintain a resolution of 3.6 seconds (or better).

Histogram tracks value counts in long fields. Smaller field types are available in the IntCountsHistogram and ShortCountsHistogram implementations of AbstractHistogram.

Auto-resizing: When constructed with no specified value range range (or when auto-resize is turned on with AbstractHistogram.setAutoResize(boolean)) a Histogram will auto-resize its dynamic range to include recorded values as they are encountered. Note that recording calls that cause auto-resizing may take longer to execute, as resizing incurrs allocation and copying of internal data structures.

See package description for org.HdrHistogram for details.

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from class org.HdrHistogram.AbstractHistogram

AbstractHistogram.AllValues, AbstractHistogram.LinearBucketValues, AbstractHistogram.LogarithmicBucketValues, AbstractHistogram.Percentiles, AbstractHistogram.RecordedValues

Constructor Summary

Histogram(AbstractHistogram source)
Construct a histogram with the same range settings as a given source histogram, duplicating the source's start/end timestamps (but NOT its contents)

Histogram(int numberOfSignificantValueDigits)
Construct an auto-resizing histogram with a lowest discernible value of 1 and an auto-adjusting highestTrackableValue.

Histogram(long highestTrackableValue, int numberOfSignificantValueDigits)
Construct a Histogram given the Highest value to be tracked and a number of significant decimal digits.

Histogram(long lowestDiscernibleValue, long highestTrackableValue, int numberOfSignificantValueDigits)
Construct a Histogram given the Lowest and Highest values to be tracked and a number of significant decimal digits.

Method Summary

Histogram	copy() Create a copy of this histogram, complete with data and everything.
Histogram	copyCorrectedForCoordinatedOmission(long expectedIntervalBetweenValueSamples) Get a copy of this histogram, corrected for coordinated omission.
static Histogram	decodeFromByteBuffer(ByteBuffer buffer, long minBarForHighestTrackableValue) Construct a new histogram by decoding it from a ByteBuffer.
static Histogram	decodeFromCompressedByteBuffer(ByteBuffer buffer, long minBarForHighestTrackableValue) Construct a new histogram by decoding it from a compressed form in a ByteBuffer.
long	getTotalCount() Get the total count of all recorded values in the histogram

Methods inherited from class org.HdrHistogram.AbstractHistogram

add, addWhileCorrectingForCoordinatedOmission, allValues, copyInto, copyIntoCorrectedForCoordinatedOmission, encodeIntoByteBuffer, encodeIntoCompressedByteBuffer, encodeIntoCompressedByteBuffer, equals, getCountAtValue, getCountBetweenValues, getEndTimeStamp, getEstimatedFootprintInBytes, getHighestTrackableValue, getLowestDiscernibleValue, getMaxValue, getMaxValueAsDouble, getMean, getMinNonZeroValue, getMinValue, getNeededByteBufferCapacity, getNumberOfSignificantValueDigits, getPercentileAtOrBelowValue, getStartTimeStamp, getStdDeviation, getValueAtPercentile, highestEquivalentValue, isAutoResize, linearBucketValues, logarithmicBucketValues, lowestEquivalentValue, medianEquivalentValue, nextNonEquivalentValue, outputPercentileDistribution, outputPercentileDistribution, outputPercentileDistribution, percentiles, recordedValues, recordValue, recordValue, recordValueWithCount, recordValueWithExpectedInterval, reset, setAutoResize, setEndTimeStamp, setStartTimeStamp, shiftValuesLeft, shiftValuesRight, sizeOfEquivalentValueRange, subtract, valuesAreEquivalent

Methods inherited from class java.lang.Object

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

Constructor Detail

Histogram

public Histogram(int numberOfSignificantValueDigits)

Construct an auto-resizing histogram with a lowest discernible value of 1 and an auto-adjusting highestTrackableValue. Can auto-reize up to track values up to (Long.MAX_VALUE / 2).

Parameters:

numberOfSignificantValueDigits - Specifies the precision to use. This is the number of significant decimal digits to which the histogram will maintain value resolution and separation. Must be a non-negative integer between 0 and 5.

Histogram

public Histogram(long highestTrackableValue,
                 int numberOfSignificantValueDigits)

Construct a Histogram given the Highest value to be tracked and a number of significant decimal digits. The histogram will be constructed to implicitly track (distinguish from 0) values as low as 1.

Parameters:

highestTrackableValue - The highest value to be tracked by the histogram. Must be a positive integer that is >= 2.

numberOfSignificantValueDigits - Specifies the precision to use. This is the number of significant decimal digits to which the histogram will maintain value resolution and separation. Must be a non-negative integer between 0 and 5.

Histogram

public Histogram(long lowestDiscernibleValue,
                 long highestTrackableValue,
                 int numberOfSignificantValueDigits)

Construct a Histogram given the Lowest and Highest values to be tracked and a number of significant decimal digits. Providing a lowestDiscernibleValue is useful is situations where the units used for the histogram's values are much smaller that the minimal accuracy required. E.g. when tracking time values stated in nanosecond units, where the minimal accuracy required is a microsecond, the proper value for lowestDiscernibleValue would be 1000.

Parameters:

lowestDiscernibleValue - The lowest value that can be discerned (distinguished from 0) by the histogram. Must be a positive integer that is >= 1. May be internally rounded down to nearest power of 2.

highestTrackableValue - The highest value to be tracked by the histogram. Must be a positive integer that is >= (2 * lowestDiscernibleValue).

numberOfSignificantValueDigits - Specifies the precision to use. This is the number of significant decimal digits to which the histogram will maintain value resolution and separation. Must be a non-negative integer between 0 and 5.

Histogram

public Histogram(AbstractHistogram source)

Construct a histogram with the same range settings as a given source histogram, duplicating the source's start/end timestamps (but NOT its contents)

Parameters:

source - The source histogram to duplicate

Method Detail

copy

public Histogram copy()

Description copied from class: AbstractHistogram

Create a copy of this histogram, complete with data and everything.

Specified by:

copy in class AbstractHistogram

Returns:

A distinct copy of this histogram.

copyCorrectedForCoordinatedOmission

public Histogram copyCorrectedForCoordinatedOmission(long expectedIntervalBetweenValueSamples)

Description copied from class: AbstractHistogram

Get a copy of this histogram, corrected for coordinated omission.

To compensate for the loss of sampled values when a recorded value is larger than the expected interval between value samples, the new histogram will include an auto-generated additional series of decreasingly-smaller (down to the expectedIntervalBetweenValueSamples) value records for each count found in the current histogram that is larger than the expectedIntervalBetweenValueSamples. Note: This is a post-correction method, as opposed to the at-recording correction method provided by recordValueWithExpectedInterval. The two methods are mutually exclusive, and only one of the two should be be used on a given data set to correct for the same coordinated omission issue. by

See notes in the description of the Histogram calls for an illustration of why this corrective behavior is important.

Specified by:

copyCorrectedForCoordinatedOmission in class AbstractHistogram

Parameters:

expectedIntervalBetweenValueSamples - If expectedIntervalBetweenValueSamples is larger than 0, add auto-generated value records as appropriate if value is larger than expectedIntervalBetweenValueSamples

Returns:

a copy of this histogram, corrected for coordinated omission.

getTotalCount

public long getTotalCount()

Description copied from class: AbstractHistogram

Get the total count of all recorded values in the histogram

Specified by:

getTotalCount in class AbstractHistogram

Returns:

the total count of all recorded values in the histogram

decodeFromByteBuffer

public static Histogram decodeFromByteBuffer(ByteBuffer buffer,
                                             long minBarForHighestTrackableValue)

Construct a new histogram by decoding it from a ByteBuffer.

Parameters:

buffer - The buffer to decode from

minBarForHighestTrackableValue - Force highestTrackableValue to be set at least this high

Returns:

The newly constructed histogram

decodeFromCompressedByteBuffer

public static Histogram decodeFromCompressedByteBuffer(ByteBuffer buffer,
                                                       long minBarForHighestTrackableValue)
                                                throws DataFormatException

Construct a new histogram by decoding it from a compressed form in a ByteBuffer.

Parameters:

buffer - The buffer to decode from

minBarForHighestTrackableValue - Force highestTrackableValue to be set at least this high

Returns:

The newly constructed histogram

Throws:

DataFormatException - on error parsing/decompressing the buffer