Package org.HdrHistogram

Class PackedConcurrentDoubleHistogram

java.lang.Object
org.HdrHistogram.EncodableHistogram
org.HdrHistogram.DoubleHistogram
org.HdrHistogram.ConcurrentDoubleHistogram
org.HdrHistogram.PackedConcurrentDoubleHistogram
All Implemented Interfaces:
Serializable, DoubleValueRecorder
public class PackedConcurrentDoubleHistogram extends ConcurrentDoubleHistogram

A floating point values High Dynamic Range (HDR) Histogram that uses a packed internal representation and supports safe concurrent recording operations.

A PackedConcurrentDoubleHistogram is a variant of DoubleHistogram that guarantees lossless recording of values into the histogram even when the histogram is updated by multiple threads, and supports auto-resize and auto-ranging operations that may occur concurrently as a result of recording operations.

PackedConcurrentDoubleHistogram tracks value counts in a packed internal representation optimized for typical histogram recoded values are sparse in the value range and tend to be incremented in small unit counts. This packed representation tends to require significantly smaller amounts of storage when compared to unpacked representations, but can incur additional recording cost due to resizing and repacking operations that may occur as previously unrecorded values are encountered.

It is important to note that concurrent recording, auto-sizing, and value shifting are the only thread-safe behaviors provided by PackedConcurrentDoubleHistogram, and that it is not otherwise synchronized. Specifically, PackedConcurrentDoubleHistogram provides no implicit synchronization that would prevent the contents of the histogram from changing during queries, iterations, copies, or addition operations on the histogram. Callers wishing to make potentially concurrent, multi-threaded updates that would safely work in the presence of queries, copies, or additions of histogram objects should either take care to externally synchronize and/or order their access, use the DoubleRecorder or SingleWriterDoubleRecorder which are intended for this purpose.

PackedConcurrentDoubleHistogram supports the recording and analyzing sampled data value counts across a configurable dynamic range of floating point (double) values, with configurable value precision within the range. Dynamic range is expressed as a ratio between the highest and lowest non-zero values trackable within the histogram at any given time. Value precision is expressed as the number of significant [decimal] 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.

Auto-ranging: Unlike integer value based histograms, the specific value range tracked by a PackedConcurrentDoubleHistogram is not specified upfront. Only the dynamic range of values that the histogram can cover is (optionally) specified. E.g. When a PackedConcurrentDoubleHistogram is created to track a dynamic range of 3600000000000 (enough to track values from a nanosecond to an hour), values could be recorded into into it in any consistent unit of time as long as the ratio between the highest and lowest non-zero values stays within the specified dynamic range, so recording in units of nanoseconds (1.0 thru 3600000000000.0), milliseconds (0.000001 thru 3600000.0) seconds (0.000000001 thru 3600.0), hours (1/3.6E12 thru 1.0) will all work just as well.

Auto-resizing: When constructed with no specified dynamic range (or when auto-resize is turned on with DoubleHistogram.setAutoResize(boolean)) a PackedConcurrentDoubleHistogram 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.

Attempts to record non-zero values that range outside of the specified dynamic range (or exceed the limits of of dynamic range when auto-resizing) may results in ArrayIndexOutOfBoundsException exceptions, either due to overflow or underflow conditions. These exceptions will only be thrown if recording the value would have resulted in discarding or losing the required value precision of values already recorded in the histogram.

See package description for org.HdrHistogram for details.

See Also:

  • Constructor Details

    • PackedConcurrentDoubleHistogram

      public PackedConcurrentDoubleHistogram(int numberOfSignificantValueDigits)
      Construct a new auto-resizing DoubleHistogram using a precision stated as a number of significant decimal digits.
      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.

    • PackedConcurrentDoubleHistogram

      public PackedConcurrentDoubleHistogram(long highestToLowestValueRatio, int numberOfSignificantValueDigits)
      Construct a new DoubleHistogram with the specified dynamic range (provided in highestToLowestValueRatio) and using a precision stated as a number of significant decimal digits.
      Parameters:
      highestToLowestValueRatio - specifies the dynamic range to use
      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.

    • PackedConcurrentDoubleHistogram

      public PackedConcurrentDoubleHistogram(DoubleHistogram source)
      Construct a PackedConcurrentDoubleHistogram with the same range settings as a given source, duplicating the source's start/end timestamps (but NOT it's contents)
      Parameters:
      source - The source histogram to duplicate

  • Method Details

    • decodeFromByteBuffer

      public static PackedConcurrentDoubleHistogram decodeFromByteBuffer(ByteBuffer buffer, long minBarForHighestToLowestValueRatio)
      Construct a new ConcurrentDoubleHistogram by decoding it from a ByteBuffer.
      Parameters:
      buffer - The buffer to decode from
      minBarForHighestToLowestValueRatio - Force highestTrackableValue to be set at least this high
      Returns:
      The newly constructed ConcurrentDoubleHistogram

    • decodeFromCompressedByteBuffer

      public static PackedConcurrentDoubleHistogram decodeFromCompressedByteBuffer(ByteBuffer buffer, long minBarForHighestToLowestValueRatio) throws DataFormatException
      Construct a new ConcurrentDoubleHistogram by decoding it from a compressed form in a ByteBuffer.
      Parameters:
      buffer - The buffer to decode from
      minBarForHighestToLowestValueRatio - Force highestTrackableValue to be set at least this high
      Returns:
      The newly constructed ConcurrentDoubleHistogram
      Throws:
      DataFormatException - on error parsing/decompressing the buffer