library-ts/browser/random/LCG.ts

import { SeedableRandomEngine } from "./RandomEngine";

export class LCGState
{
  public modulus:number;
  public multiplier:number;
  public increment:number;
  public state:number;  
}

export class LCG extends SeedableRandomEngine<LCGState>
{    
  private _seedState:LCGState  = new LCGState();
  private _normalizer:number; 

  constructor()
  {
    super();
    this.setParameters( Math.pow( 2, 32 ), 1664525, 1013904223 );
  }

  setParameters( modulus:number, multiplier:number, increment:number ):void
  {
    this._seedState.modulus    = modulus;
    this._seedState.multiplier = multiplier;
    this._seedState.increment  = increment;
    this._seedState.state      = 0;
    this._normalizer = 1  / ( this._seedState.modulus );   
  }

  getSeedState()
  {
    var seedState = new LCGState();

    seedState.modulus = this._seedState.modulus;
    seedState.multiplier = this._seedState.multiplier;
    seedState.increment = this._seedState.increment;
    seedState.state = this._seedState.state;  

    return seedState;
  }

  setSeedState( seedState:LCGState )
  {
    this._seedState.modulus    = seedState.modulus;
    this._seedState.multiplier = seedState.multiplier;
    this._seedState.increment  = seedState.increment;
    this._seedState.state      = seedState.state;
    this._normalizer = 1 / ( this._seedState.modulus );   
  }

  next()
  {
    this._seedState.state = ( this._seedState.state * this._seedState.multiplier +
       this._seedState.increment) % this._seedState.modulus;
    var value = this._seedState.state * this._normalizer;
    return Math.abs( value );
  }
  
  setSeed( seed:number )
  {
    this._seedState.state = seed % this._seedState.modulus;      
  }

  warmUp( runs:number = 1000 )
  {
    for ( let i = 0; i < runs; i++)
    {
      this.next();
    }
  }
  
}