Package org.HdrHistogram

Class Histogram

java.lang.Object
org.HdrHistogram.EncodableHistogram
org.HdrHistogram.AbstractHistogramBase
org.HdrHistogram.AbstractHistogram
org.HdrHistogram.Histogram
All Implemented Interfaces:
Serializable, ValueRecorder
Direct Known Subclasses:
AtomicHistogram, ConcurrentHistogram, PackedHistogram, SingleWriterRecorder.InternalHistogram, 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 incurs allocation and copying of internal data structures.

See package description for org.HdrHistogram for details.

See Also:

  • Field Details

    • totalCount

      long totalCount

    • counts

      long[] counts

    • normalizingIndexOffset

      int normalizingIndexOffset

  • Constructor Details

    • Histogram

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

    • Histogram

      Histogram(AbstractHistogram source, boolean allocateCountsArray)

    • Histogram

      Histogram(long lowestDiscernibleValue, long highestTrackableValue, int numberOfSignificantValueDigits, boolean allocateCountsArray)

  • Method Details

    • getCountAtIndex

      long getCountAtIndex(int index)
      Specified by:
      getCountAtIndex in class AbstractHistogram

    • getCountAtNormalizedIndex

      long getCountAtNormalizedIndex(int index)
      Specified by:
      getCountAtNormalizedIndex in class AbstractHistogram

    • incrementCountAtIndex

      void incrementCountAtIndex(int index)
      Specified by:
      incrementCountAtIndex in class AbstractHistogram

    • addToCountAtIndex

      void addToCountAtIndex(int index, long value)
      Specified by:
      addToCountAtIndex in class AbstractHistogram

    • setCountAtIndex

      void setCountAtIndex(int index, long value)
      Specified by:
      setCountAtIndex in class AbstractHistogram

    • setCountAtNormalizedIndex

      void setCountAtNormalizedIndex(int index, long value)
      Specified by:
      setCountAtNormalizedIndex in class AbstractHistogram

    • getNormalizingIndexOffset

      int getNormalizingIndexOffset()
      Specified by:
      getNormalizingIndexOffset in class AbstractHistogram

    • setNormalizingIndexOffset

      void setNormalizingIndexOffset(int normalizingIndexOffset)
      Specified by:
      setNormalizingIndexOffset in class AbstractHistogram

    • setIntegerToDoubleValueConversionRatio

      void setIntegerToDoubleValueConversionRatio(double integerToDoubleValueConversionRatio)
      Specified by:
      setIntegerToDoubleValueConversionRatio in class AbstractHistogramBase

    • shiftNormalizingIndexByOffset

      void shiftNormalizingIndexByOffset(int offsetToAdd, boolean lowestHalfBucketPopulated, double newIntegerToDoubleValueConversionRatio)
      Specified by:
      shiftNormalizingIndexByOffset in class AbstractHistogram

    • clearCounts

      void clearCounts()
      Specified by:
      clearCounts in class AbstractHistogram

    • 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

    • setTotalCount

      void setTotalCount(long totalCount)
      Specified by:
      setTotalCount in class AbstractHistogram

    • incrementTotalCount

      void incrementTotalCount()
      Specified by:
      incrementTotalCount in class AbstractHistogram

    • addToTotalCount

      void addToTotalCount(long value)
      Specified by:
      addToTotalCount in class AbstractHistogram

    • _getEstimatedFootprintInBytes

      int _getEstimatedFootprintInBytes()
      Specified by:
      _getEstimatedFootprintInBytes in class AbstractHistogram

    • resize

      void resize(long newHighestTrackableValue)
      Specified by:
      resize in class AbstractHistogram

    • 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

    • readObject

      private void readObject(ObjectInputStream o) throws IOException, ClassNotFoundException
      Throws:
      IOException
      ClassNotFoundException

    • fromString

      public static Histogram fromString(String base64CompressedHistogramString) throws DataFormatException
      Construct a new Histogram by decoding it from a String containing a base64 encoded compressed histogram representation.
      Parameters:
      base64CompressedHistogramString - A string containing a base64 encoding of a compressed histogram
      Returns:
      A Histogram decoded from the string
      Throws:
      DataFormatException - on error parsing/decompressing the input