Package org.orekit.utils

Class GenericTimeStampedCache<T extends TimeStamped>

java.lang.Object
org.orekit.utils.GenericTimeStampedCache<T>
Type Parameters:
T - Type of the cached data.
All Implemented Interfaces:
TimeStampedCache<T>
public class GenericTimeStampedCache<T extends TimeStamped> extends Object implements TimeStampedCache<T>
Generic thread-safe cache for time-stamped data.
Author:
Luc Maisonobe

  • Field Details

    • DEFAULT_CACHED_SLOTS_NUMBER

      public static final int DEFAULT_CACHED_SLOTS_NUMBER
      Default number of independent cached time slots.
      See Also:

  • Constructor Details

    • GenericTimeStampedCache

      public GenericTimeStampedCache(int maxNeighborsSize, int maxSlots, double maxSpan, double newSlotInterval, TimeStampedGenerator<T> generator)
      Simple constructor.
      Parameters:
      maxNeighborsSize - maximum size of the arrays to be returned by getNeighbors(AbsoluteDate, int), must be at least 2
      maxSlots - maximum number of independent cached time slots
      maxSpan - maximum duration span in seconds of one slot (can be set to Double.POSITIVE_INFINITY if desired)
      newSlotInterval - time interval above which a new slot is created instead of extending an existing one
      generator - generator to use for yet non-existent data

    • GenericTimeStampedCache

      public GenericTimeStampedCache(int maxNeighborsSize, int maxSlots, double maxSpan, double newSlotInterval, TimeStampedGenerator<T> generator, double overridingMeanStep)
      Simple constructor with overriding minimum step.
      Parameters:
      maxNeighborsSize - maximum size of the arrays to be returned by getNeighbors(AbsoluteDate, int), must be at least 2
      maxSlots - maximum number of independent cached time slots
      maxSpan - maximum duration span in seconds of one slot (can be set to Double.POSITIVE_INFINITY if desired)
      newSlotInterval - time interval above which a new slot is created instead of extending an existing one
      generator - generator to use for yet non-existent data
      overridingMeanStep - overriding mean step designed for non-homogeneous tabulated values. To be used for example when caching monthly tabulated values. Use Double.NaN otherwise.
      Throws:
      OrekitIllegalArgumentException - if :
      • neighbors size < 2
      • maximum allowed number of slots < 1
      • minimum step ≤ 0

  • Method Details

    • getGenerator

      public TimeStampedGenerator<T> getGenerator()
      Get the generator.
      Returns:
      generator

    • getMaxSlots

      public int getMaxSlots()
      Get the maximum number of independent cached time slots.
      Returns:
      maximum number of independent cached time slots

    • getMaxSpan

      public double getMaxSpan()
      Get the maximum duration span in seconds of one slot.
      Returns:
      maximum duration span in seconds of one slot

    • getNewSlotQuantumGap

      public double getNewSlotQuantumGap()
      Get quantum gap above which a new slot is created instead of extending an existing one.

      The quantum gap is the newSlotInterval value provided at construction rounded to the nearest quantum step used internally by the cache.

      Returns:
      quantum gap in seconds

    • getGetNeighborsCalls

      public int getGetNeighborsCalls()
      Get the number of calls to the TimeStampedCache.getNeighbors(AbsoluteDate) method.

      This number of calls is used as a reference to interpret getGenerateCalls().

      Returns:
      number of calls to the TimeStampedCache.getNeighbors(AbsoluteDate) method
      See Also:

    • getGenerateCalls

      public int getGenerateCalls()
      Get the number of calls to the generate method.

      This number of calls is related to the number of cache misses and may be used to tune the cache configuration. Each cache miss implies at least one call is performed, but may require several calls if the new date is far offset from the existing cache, depending on the number of elements and step between elements in the arrays returned by the generator.

      Returns:
      number of calls to the generate method
      See Also:

    • getSlotsEvictions

      public int getSlotsEvictions()
      Get the number of slots evictions.

      This number should remain small when the max number of slots is sufficient with respect to the number of concurrent requests to the cache. If it increases too much, then the cache configuration is probably bad and cache does not really improve things (in this case, the number of calls to the generate method will probably increase too.

      Returns:
      number of slots evictions

    • getSlots

      public int getSlots()
      Get the number of slots in use.
      Returns:
      number of slots in use

    • getEntries

      public int getEntries()
      Get the total number of entries cached.
      Returns:
      total number of entries cached

    • getEarliest

      public T getEarliest() throws IllegalStateException
      Get the earliest entry in this cache.
      Specified by:
      getEarliest in interface TimeStampedCache<T extends TimeStamped>
      Returns:
      earliest cached entry
      Throws:
      IllegalStateException - if this cache is empty

    • getLatest

      public T getLatest() throws IllegalStateException
      Get the latest entry in this cache.
      Specified by:
      getLatest in interface TimeStampedCache<T extends TimeStamped>
      Returns:
      latest cached entry
      Throws:
      IllegalStateException - if this cache is empty

    • getMaxNeighborsSize

      public int getMaxNeighborsSize()
      Get the maximum size of the lists returned by TimeStampedCache.getNeighbors(AbsoluteDate, int).
      Specified by:
      getMaxNeighborsSize in interface TimeStampedCache<T extends TimeStamped>
      Returns:
      size of the list

    • getNeighbors

      public Stream<T> getNeighbors(AbsoluteDate central, int n)
      Get the entries surrounding a central date.

      If the central date is well within covered range, the returned array will be balanced with half the points before central date and half the points after it (depending on n parity, of course). If the central date is near the boundary, then the returned array will be unbalanced and will contain only the n earliest (or latest) entries. A typical example of the later case is leap seconds cache, since the number of leap seconds cannot be arbitrarily increased.

      This method is safe for multiple threads to execute concurrently.

      Specified by:
      getNeighbors in interface TimeStampedCache<T extends TimeStamped>
      Parameters:
      central - central date
      n - number of neighbors (cannot exceed TimeStampedCache.getMaxNeighborsSize())
      Returns:
      stream of cached entries surrounding the specified date.