PackedDoubleHistogram.java
/**
* Written by Gil Tene of Azul Systems, and released to the public domain,
* as explained at http://creativecommons.org/publicdomain/zero/1.0/
*
* @author Gil Tene
*/
package org.HdrHistogram;
import java.nio.ByteBuffer;
import java.util.zip.DataFormatException;
/**
* <h3>A floating point values High Dynamic Range (HDR) Histogram that uses a packed internal representation</h3>
* <p>
* It is important to note that {@link PackedDoubleHistogram} is not thread-safe, and does not support safe concurrent
* recording by multiple threads. If concurrent operation is required, consider using
* {@link PackedConcurrentDoubleHistogram}, or (recommended) {@link DoubleRecorder} or
* {@link SingleWriterDoubleRecorder} which are intended for this purpose.
* <p>
* {@link PackedDoubleHistogram} 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.
* <p>
* {@link PackedDoubleHistogram} 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.
* <p>
* Auto-ranging: Unlike integer value based histograms, the specific value range tracked by a {@link
* PackedDoubleHistogram} is not specified upfront. Only the dynamic range of values that the histogram can cover is
* (optionally) specified. E.g. When a {@link PackedDoubleHistogram} 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.
* <p>
* Auto-resizing: When constructed with no specified dynamic range (or when auto-resize is turned on with {@link
* DoubleHistogram#setAutoResize}) a {@link DoubleHistogram} 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.
* <p>
* 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 {@link 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.
* <p>
* See package description for {@link org.HdrHistogram} for details.
*/
public class PackedDoubleHistogram extends DoubleHistogram {
/**
* Construct a new auto-resizing DoubleHistogram using a precision stated as a number of significant decimal
* digits.
*
* @param 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.
*/
public PackedDoubleHistogram(final int numberOfSignificantValueDigits) {
this(2, numberOfSignificantValueDigits);
setAutoResize(true);
}
/**
* Construct a new DoubleHistogram with the specified dynamic range (provided in {@code highestToLowestValueRatio})
* and using a precision stated as a number of significant decimal digits.
*
* @param highestToLowestValueRatio specifies the dynamic range to use
* @param 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.
*/
public PackedDoubleHistogram(final long highestToLowestValueRatio, final int numberOfSignificantValueDigits) {
this(highestToLowestValueRatio, numberOfSignificantValueDigits, PackedHistogram.class);
}
/**
* Construct a {@link PackedDoubleHistogram} with the same range settings as a given source,
* duplicating the source's start/end timestamps (but NOT it's contents)
* @param source The source histogram to duplicate
*/
public PackedDoubleHistogram(final DoubleHistogram source) {
super(source);
}
PackedDoubleHistogram(final long highestToLowestValueRatio,
final int numberOfSignificantValueDigits,
final Class<? extends AbstractHistogram> internalCountsHistogramClass) {
super(highestToLowestValueRatio, numberOfSignificantValueDigits, internalCountsHistogramClass);
}
PackedDoubleHistogram(final long highestToLowestValueRatio,
final int numberOfSignificantValueDigits,
final Class<? extends AbstractHistogram> internalCountsHistogramClass,
AbstractHistogram internalCountsHistogram) {
super(
highestToLowestValueRatio,
numberOfSignificantValueDigits,
internalCountsHistogramClass,
internalCountsHistogram
);
}
/**
* Construct a new ConcurrentDoubleHistogram by decoding it from a ByteBuffer.
* @param buffer The buffer to decode from
* @param minBarForHighestToLowestValueRatio Force highestTrackableValue to be set at least this high
* @return The newly constructed ConcurrentDoubleHistogram
*/
public static PackedDoubleHistogram decodeFromByteBuffer(
final ByteBuffer buffer,
final long minBarForHighestToLowestValueRatio) {
try {
int cookie = buffer.getInt();
if (!isNonCompressedDoubleHistogramCookie(cookie)) {
throw new IllegalArgumentException("The buffer does not contain a DoubleHistogram");
}
PackedDoubleHistogram histogram = constructHistogramFromBuffer(cookie, buffer,
PackedDoubleHistogram.class, PackedHistogram.class,
minBarForHighestToLowestValueRatio);
return histogram;
} catch (DataFormatException ex) {
throw new RuntimeException(ex);
}
}
/**
* Construct a new ConcurrentDoubleHistogram by decoding it from a compressed form in a ByteBuffer.
* @param buffer The buffer to decode from
* @param minBarForHighestToLowestValueRatio Force highestTrackableValue to be set at least this high
* @return The newly constructed ConcurrentDoubleHistogram
* @throws DataFormatException on error parsing/decompressing the buffer
*/
public static PackedDoubleHistogram decodeFromCompressedByteBuffer(
final ByteBuffer buffer,
final long minBarForHighestToLowestValueRatio) throws DataFormatException {
int cookie = buffer.getInt();
if (!isCompressedDoubleHistogramCookie(cookie)) {
throw new IllegalArgumentException("The buffer does not contain a compressed DoubleHistogram");
}
PackedDoubleHistogram histogram = constructHistogramFromBuffer(cookie, buffer,
PackedDoubleHistogram.class, PackedHistogram.class,
minBarForHighestToLowestValueRatio);
return histogram;
}
}