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SSJ is a Java library for stochastic simulation, developed under the direction of Pierre L'Ecuyer,
in the Département d'Informatique et de Recherche Opérationnelle (DIRO), at the Université de Montréal.
It provides facilities for generating uniform and nonuniform random variates, computing different
measures related to probability distributions, performing goodness-of-fit tests, applying quasi-Monte
Carlo methods, collecting (elementary) statistics, and programming discrete-event simulations with both
events and processes.
/*
* Class: F2wStructure
* Description: Tools for point sets and sequences based on field F_{2^w}
* Environment: Java
* Software: SSJ
* Copyright (C) 2001 Pierre L'Ecuyer and Université de Montréal
* Organization: DIRO, Université de Montréal
* @author
* @since
* SSJ is free software: you can redistribute it and/or modify it under
* the terms of the GNU General Public License (GPL) as published by the
* Free Software Foundation, either version 3 of the License, or
* any later version.
* SSJ is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
* A copy of the GNU General Public License is available at
GPL licence site.
*/
package umontreal.iro.lecuyer.hups;
import java.io.*;
import java.util.*;
/**
* This class implements methods and fields needed by the classes
* {@link umontreal.iro.lecuyer.hups.F2wNetLFSR F2wNetLFSR},
* {@link umontreal.iro.lecuyer.hups.F2wNetPolyLCG F2wNetPolyLCG},
* {@link umontreal.iro.lecuyer.hups.F2wCycleBasedLFSR F2wCycleBasedLFSR} and
* {@link umontreal.iro.lecuyer.hups.F2wCycleBasedPolyLCG F2wCycleBasedPolyLCG}.
* It also stores the parameters of these point sets which will contain
* 2rw points (see the meaning of r and w below).
* The parameters can be stored as a polynomial P(z) over
*
* F2w[z]
*
*
*
* P(z) = zr + ∑i=1rbizr-i
*
* where
* bi∈F2w for
* i = 1,…, r.
* Let ζ be the root of an irreducible polynomial
*
* Q(z)∈F2[z]. It is well known
* that ζ is a generator of the finite field
*
* F2w.
* The elements of
* F2w are
* represented using the polynomial ordered
* basis
* (1, ζ,…, ζw-1).
*
*
* In this class, only the non-zero coefficients of P(z) are stored.
* It is stored as
*
*
*
* P(z) = zr + ∑i=0nbcoeffcoeff[i]znocoeff[i]
*
* where the coefficients in coeff[] represent the non-zero
* coefficients bi of P(z) using the polynomial basis.
* The finite field
* F2w used is
* defined by the polynomial
*
*
*
* Q(z) = zw + ∑i=1waizw-i
*
* where
* ai∈F2,
* for
* i = 1,…, w. Polynomial Q is
* stored as the bit vector modQ =
* (aw,…, a1).
*
*
* The class also stores the parameter step that is used by the classes
* {@link umontreal.iro.lecuyer.hups.F2wNetLFSR F2wNetLFSR},
* {@link umontreal.iro.lecuyer.hups.F2wNetPolyLCG F2wNetPolyLCG},
* {@link umontreal.iro.lecuyer.hups.F2wCycleBasedLFSR F2wCycleBasedLFSR} and
* {@link umontreal.iro.lecuyer.hups.F2wCycleBasedPolyLCG F2wCycleBasedPolyLCG}.
* This parameter is such that the implementation of the recurrence
* will output a value at every step iterations.
*
*/
public class F2wStructure {
private final int ALLONES = 2147483647; // 2^31-1 --> 01111...1
int w;
int r;
int numBits;
private int modQ;
private int step;
private int[] coeff;
private int[] nocoeff;
private int nbcoeff;
int S;
private int maskw;
private int maskrw;
private int maskZrm1;
private int mask31;
private int t;
private int masktrw;
private int[] maskv;
int state;
int output; // augmented state
double normFactor;
double EpsilonHalf;
final static int MBL = 140; //maximum of bytes in 1 line
//92 bytes for a number of coeff = 15
private void init (int w, int r, int modQ, int step,
int nbcoeff, int coeff[], int nocoeff[])
{
normFactor = 1.0 / (1L << 31); // 4.65661287307739258e-10;
EpsilonHalf = 0.5*normFactor;
numBits = 31;
this.step = step;
this.w = w;
this.r = r;
S = 31 - r * w;
mask31 = ~(1 << 31);
maskw = (1 << w) - 1;
maskrw = ((1 << (r * w)) - 1) << S;
maskZrm1 = (ALLONES >> (r * w)) ^ (ALLONES >> ((r - 1) * w));
this.modQ = modQ;
this.nbcoeff = nbcoeff;
this.nocoeff = new int[nbcoeff];
this.coeff = new int[nbcoeff];
for (int j = 0; j < nbcoeff; j++) {
this.nocoeff[j] = nocoeff[j];
this.coeff[j] = coeff[j];
}
}
void initParamLFSR ()
{
t = (31 - r * w) / w;
masktrw = (~0) << (31 - (t + r) * w) & mask31;
maskv = new int[r];
for (int j = 0; j < r; j++) {
maskv[j] = maskw << (S + ((r - 1 - j) * w));
}
}
/**
* Constructs a F2wStructure object that contains the parameters of a
* polynomial in
* F2w[z],
* as well as a stepping parameter.
*
*/
F2wStructure (int w, int r, int modQ, int step, int nbcoeff,
int coeff[], int nocoeff[])
{
init (w, r, modQ, step, nbcoeff, coeff, nocoeff);
}
/**
* Constructs a polynomial in
* F2w[z]
* after reading its parameters from file filename;
* the parameters of this polynomial are stored at line number
* no of filename.
* The files are kept in different
* directories depending on the criteria used in the searches for the
* parameters defining the polynomials. The different criteria for the
* searches and the theory behind it are described in.
* The existing files and the number of polynomials they contain are
* given in the following tables.
* The first table below contains files in subdirectory
* LFSR_equid_max. The name of each
* file indicates the value of r and w for the polynomials.
* For example, file f2wR2_W5.dat in directory
* LFSR_equid_max contains the parameters of 2358
* polynomials with r = 2 and w = 5. For example, to use the 5-th
* polynomial of file f2wR2_W5.dat, one may call
* F2wStructure("f2wR2_W5.dat", 5).
* The files of parameters have been stored at the address
* http://www.iro.umontreal.ca/~simardr/ssj-1/dataF2w/.
*
*/
F2wStructure (String filename, int no)
{
// If filename can be found starting from the program's directory,
// it will be used; otherwise, the filename in the Jar archive will
// be used.
BufferedReader input;
try {
if ((new File (filename)).exists()) {
input = new BufferedReader (new FileReader (filename));
} else {
DataInputStream dataInput;
dataInput = new DataInputStream (
F2wStructure.class.getClassLoader().getResourceAsStream (
"umontreal/iro/lecuyer/hups/dataF2w/" + filename));
input = new BufferedReader (new InputStreamReader (dataInput));
}
initFromReader (filename, input, no);
input.close ();
} catch (Exception e) {
System.out.println ("IO Error: problems finding file " + filename);
System.exit (1);
}
}
private int multiplyz (int a, int k)
{
int i;
if (k == 0)
return a & maskw;
else {
for (i = 0; i < k; i++) {
if ((1 & a) == 1) {
a = (a >> 1) ^ modQ;
} else
a = a >> 1;
}
return a & maskw;
}
}
/**
* This method returns the product rw.
*
*/
int getLog2N ()
{
return r * w;
}
/**
* Method that multiplies two elements in
*
* F2w.
*
*/
int multiply (int a, int b)
{
int i;
int res = 0, verif = 1;
for (i = 0; i < w; i++) {
if ((b & verif) == verif)
res ^= multiplyz (a, w - 1 - i);
verif <<= 1;
}
return res & maskw;
}
void initF2wLFSR () // Initialisation de l'etat d'un LFSR
{
int v, d = 0;
int tempState;
tempState = state << S;
output = tempState;
for (int i = 1; i <= t; i++) {
d = 0;
for (int j = 0; j < nbcoeff; j++) {
v = (tempState & maskv[nocoeff[j]]) >>
(S + (r - 1 - nocoeff[j]) * w);
d ^= multiply (coeff[j], v);
}
output |= d << (S - i * w);
tempState = (output << (i * w)) & maskrw;
}
}
void F2wLFSR () // Une iteration d'un LFSR
{
int v, d = 0;
int tempState;
for (int i = 0; i < step; i++) {
tempState = (output << (t * w)) & maskrw;
d = 0;
for (int j = 0; j < nbcoeff; j++) {
v = (tempState & maskv[nocoeff[j]]) >>
(S + (r - 1 - nocoeff[j]) * w);
d ^= multiply (coeff[j], v);
}
output = ((output << w) & masktrw) |
(d << (31 - (r + t) * w));
}
state = (output & maskrw) >> S;
}
int F2wPolyLCG () // Une iteration d'un PolyLCG
{
int Zrm1, d;
for (int i = 0; i < step; i++) {
Zrm1 = (state & maskZrm1) >> S;
state = (state >> w) & maskrw;
for (int j = 0; j < nbcoeff; j++)
state ^=
multiply (coeff[j], Zrm1) << (S + (r - 1 - nocoeff[j]) * w);
}
return state;
}
/**
* Prints the content of file filename. See the constructor
* above for the conditions on filename.
*
*/
public static void print (String filename)
{
BufferedReader input;
try {
if ((new File (filename)).exists()) {
input = new BufferedReader (new FileReader (filename));
} else {
DataInputStream dataInput;
dataInput = new DataInputStream (
F2wStructure.class.getClassLoader().getResourceAsStream (
"umontreal/iro/lecuyer/hups/dataF2w/" + filename));
input = new BufferedReader (new InputStreamReader (dataInput));
}
String s;
for (int i = 0; i < 4; i++)
input.readLine ();
while ((s = input.readLine ()) != null)
System.out.println (s);
input.close ();
} catch (Exception e) {
System.out.println ("IO Error: problems reading file " + filename);
System.exit (1);
}
}
/**
* This method returns a string containing the polynomial P(z) and
* the stepping parameter.
*
*/
public String toString ()
{
StringBuffer sb = new StringBuffer ("z^");
sb.append (r);
for (int j = nbcoeff - 1; j >= 0; j--)
sb.append (" + (" + coeff[j] + ") z^" + nocoeff[j]);
sb.append (" modQ = " + modQ + " w = " + w + " step = " + step);
return sb.toString ();
}
private void initFromReader (String filename, BufferedReader input, int no)
{
int w, r, modQ, step, nbcoeff;
int coeff[], nocoeff[];
StringTokenizer line;
int nl = no + 4;
try {
for (int j = 1; j < nl ; j++)
input.readLine ();
line = new StringTokenizer (input.readLine ());
w = Integer.parseInt (line.nextToken ());
r = Integer.parseInt (line.nextToken ());
modQ = Integer.parseInt (line.nextToken ());
step = Integer.parseInt (line.nextToken ());
nbcoeff = Integer.parseInt (line.nextToken ());
nocoeff = new int[nbcoeff];
coeff = new int[nbcoeff];
for (int i = 0; i < nbcoeff; i++) {
coeff[i] = Integer.parseInt (line.nextToken ());
nocoeff[i] = Integer.parseInt (line.nextToken ());
}
init (w, r, modQ, step, nbcoeff, coeff, nocoeff);
input.close ();
} catch (Exception e) {
System.out.println ("Input Error: problems reading file " + filename);
System.exit (1);
}
}
}
/**
* .
*
