Package org.apache.lucene.util

Class SloppyMath

java.lang.Object
org.apache.lucene.util.SloppyMath
public class SloppyMath extends Object
Math functions that trade off accuracy for speed.

  • Constructor Summary

    Constructors
    Constructor
    Description
    SloppyMath()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    static double
    asin(double a)
    Returns the arc sine of a value.
    static double
    cos(double a)
    Returns the trigonometric cosine of an angle.
    static double
    haversinMeters(double sortKey)
    Returns the Haversine distance in meters between two points given the previous result from haversinSortKey(double, double, double, double)
    static double
    haversinMeters(double lat1, double lon1, double lat2, double lon2)
    Returns the Haversine distance in meters between two points specified in decimal degrees (latitude/longitude).
    static double
    haversinSortKey(double lat1, double lon1, double lat2, double lon2)
    Returns a sort key for distance.

    Methods inherited from class java.lang.Object

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

  • Constructor Details

    • SloppyMath

      public SloppyMath()

  • Method Details

    • haversinMeters

      public static double haversinMeters(double lat1, double lon1, double lat2, double lon2)
      Returns the Haversine distance in meters between two points specified in decimal degrees (latitude/longitude). This works correctly even if the dateline is between the two points.

      Error is at most 4E-1 (40cm) from the actual haversine distance, but is typically much smaller for reasonable distances: around 1E-5 (0.01mm) for distances less than 1000km.

      Parameters:
      lat1 - Latitude of the first point.
      lon1 - Longitude of the first point.
      lat2 - Latitude of the second point.
      lon2 - Longitude of the second point.
      Returns:
      distance in meters.

    • haversinMeters

      public static double haversinMeters(double sortKey)
      Returns the Haversine distance in meters between two points given the previous result from haversinSortKey(double, double, double, double)
      Returns:
      distance in meters.

    • haversinSortKey

      public static double haversinSortKey(double lat1, double lon1, double lat2, double lon2)
      Returns a sort key for distance. This is less expensive to compute than haversinMeters(double, double, double, double), but it always compares the same. This can be converted into an actual distance with haversinMeters(double), which effectively does the second half of the computation.

    • cos

      public static double cos(double a)
      Returns the trigonometric cosine of an angle.

      Error is around 1E-15.

      Special cases:

      • If the argument is NaN or an infinity, then the result is NaN.
      Parameters:
      a - an angle, in radians.
      Returns:
      the cosine of the argument.
      See Also:

    • asin

      public static double asin(double a)
      Returns the arc sine of a value.

      The returned angle is in the range -pi/2 through pi/2. Error is around 1E-7.

      Special cases:

      • If the argument is NaN or its absolute value is greater than 1, then the result is NaN.
      Parameters:
      a - the value whose arc sine is to be returned.
      Returns:
      arc sine of the argument
      See Also: