Package squidpony.squidmath

Class NLFSR

java.lang.Object
squidpony.squidmath.NLFSR
All Implemented Interfaces:
Serializable, RandomnessSource, StatefulRandomness
public class NLFSR
extends Object
implements StatefulRandomness, Serializable
A Non-Linear Feedback Shift Register that may be used like a StatefulRandomness but is not truly random. This is based on the LFSR class, and is less predictable but is otherwise less than optimal in some ways. It has a period of (2 to the 27) minus 1, and uses data from http://people.kth.se/~dubrova/nlfsr.html and https://eprint.iacr.org/2012/314.pdf . You would normally only prefer NLFSR over LFSR if you expect players to scrutinize your randomly-generated data, or if you want to use it as part of a more complex process such as encoding a saved file in a more robust way. Since 2 to the 27 numbers can be produced and analyzed in a matter of seconds, you'd need a lot of independent steps like this to actually improve encoding. It is important to note that an NLFSR or LFSR will produce each number from 1 until its maximum exactly once before repeating, so this may be useful as a way of generating test data in an unpredictable order.
Author:
Tommy Ettinger
See Also:
Serialized Form

  • Field Summary

    Fields 
    Modifier and Type Field Description
    int state  

  • Constructor Summary

    Constructors 
    Constructor Description
    NLFSR()
    Creates a new generator seeded using Math.random.
    NLFSR​(int seed)  
    NLFSR​(CharSequence seed)  

  • Method Summary

    Modifier and Type Method Description
    NLFSR copy()
    Produces a copy of this RandomnessSource that, if next() and/or nextLong() are called on this object and the copy, both will generate the same sequence of random numbers from the point copy() was called.
    boolean equals​(Object o)  
    long getState()
    Get the current internal state of the StatefulRandomness as a long.
    int hashCode()  
    int next​(int bits)
    Using this method, any algorithm that might use the built-in Java Random can interface with this randomness source.
    boolean nextBoolean()  
    void nextBytes​(byte[] bytes)  
    double nextDouble()  
    float nextFloat()  
    int nextInt()
    Produces up to 27 bits of random int, with a minimum result of 1 and a max of 134217727 (both inclusive).
    int nextInt​(int bound)
    Exclusive on the upper bound.
    int nextInt​(int lower, int upper)
    Inclusive lower, exclusive upper.
    long nextLong()
    Using this method, any algorithm that needs to efficiently generate more than 32 bits of random data can interface with this randomness source.
    long nextLong​(long bound)
    Exclusive on the upper bound.
    void setState​(long seed)
    Sets the seed of this generator using one long, running that through LightRNG's algorithm twice to get the state.
    String toString()  

    Methods inherited from class java.lang.Object

    clone, finalize, getClass, notify, notifyAll, wait, wait, wait

  • Field Details

  • Constructor Details

  • Method Details

    • next

      public int next​(int bits)
      Description copied from interface: RandomnessSource
      Using this method, any algorithm that might use the built-in Java Random can interface with this randomness source.
      Specified by:
      next in interface RandomnessSource
      Parameters:
      bits - the number of bits to be returned
      Returns:
      the integer containing the appropriate number of bits

    • nextLong

      public long nextLong()
      Description copied from interface: RandomnessSource
      Using this method, any algorithm that needs to efficiently generate more than 32 bits of random data can interface with this randomness source. Get a random long between Long.MIN_VALUE and Long.MAX_VALUE (both inclusive).
      Specified by:
      nextLong in interface RandomnessSource
      Returns:
      a random long between Long.MIN_VALUE and Long.MAX_VALUE (both inclusive)

    • nextInt

      public int nextInt()
      Produces up to 27 bits of random int, with a minimum result of 1 and a max of 134217727 (both inclusive).
      Returns:
      a random int between 1 and 134217727, both inclusive

    • copy

      public NLFSR copy()
      Produces a copy of this RandomnessSource that, if next() and/or nextLong() are called on this object and the copy, both will generate the same sequence of random numbers from the point copy() was called. This just needs to copy the state so it isn't shared, usually, and produce a new value with the same exact state.
      Specified by:
      copy in interface RandomnessSource
      Specified by:
      copy in interface StatefulRandomness
      Returns:
      a copy of this RandomnessSource

    • nextInt

      public int nextInt​(int bound)
      Exclusive on the upper bound. The lower bound is 0.
      Parameters:
      bound - the upper bound; should be positive
      Returns:
      a random int less than n and at least equal to 0

    • nextInt

      public int nextInt​(int lower, int upper)
      Inclusive lower, exclusive upper.
      Parameters:
      lower - the lower bound, inclusive, can be positive or negative
      upper - the upper bound, exclusive, should be positive, must be greater than lower
      Returns:
      a random int at least equal to lower and less than upper

    • nextLong

      public long nextLong​(long bound)
      Exclusive on the upper bound. The lower bound is 0.
      Parameters:
      bound - the upper bound; should be positive
      Returns:
      a random long less than n

    • nextDouble

      public double nextDouble()

    • nextFloat

      public float nextFloat()

    • nextBoolean

      public boolean nextBoolean()

    • nextBytes

      public void nextBytes​(byte[] bytes)

    • getState

      public long getState()
      Get the current internal state of the StatefulRandomness as a long.
      Specified by:
      getState in interface StatefulRandomness
      Returns:
      the current internal state of this object.

    • setState

      public void setState​(long seed)
      Sets the seed of this generator using one long, running that through LightRNG's algorithm twice to get the state.
      Specified by:
      setState in interface StatefulRandomness
      Parameters:
      seed - the number to use as the seed

    • toString

      public String toString()
      Overrides:
      toString in class Object

    • equals

      public boolean equals​(Object o)
      Overrides:
      equals in class Object

    • hashCode

      public int hashCode()
      Overrides:
      hashCode in class Object