/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */

//

//  Copyright (C) 2001  Pierre L'Ecuyer (lecuyer@iro.umontreal.ca)

//

// This program is free software; you can redistribute it and/or modify

// it under the terms of the GNU General Public License version 2 as

// published by the Free Software Foundation;

//

// This program 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.

//

// You should have received a copy of the GNU General Public License

// along with this program; if not, write to the Free Software

// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

//

// Modified for ns-3 by: Rajib Bhattacharjea<raj.b@gatech.edu>

//

#include <cstdlib>

#include <iostream>

#include "rng-stream.h"

using namespace std;

namespace

{

const double m1   =       4294967087.0;

const double m2   =       4294944443.0;

const double norm =       1.0 / (m1 + 1.0);

const double a12  =       1403580.0;

const double a13n =       810728.0;

const double a21  =       527612.0;

const double a23n =       1370589.0;

const double two17 =      131072.0;

const double two53 =      9007199254740992.0;

const double fact =       5.9604644775390625e-8;     /* 1 / 2^24  */

// The following are the transition matrices of the two MRG components

// (in matrix form), raised to the powers -1, 1, 2^76, and 2^127, resp.

const double InvA1[3][3] = {          // Inverse of A1p0

       { 184888585.0,   0.0,  1945170933.0 },

       {         1.0,   0.0,           0.0 },

       {         0.0,   1.0,           0.0 }

       };

const double InvA2[3][3] = {          // Inverse of A2p0

       {      0.0,  360363334.0,  4225571728.0 },

       {      1.0,          0.0,           0.0 },

       {      0.0,          1.0,           0.0 }

       };

const double A1p0[3][3] = {

       {       0.0,        1.0,       0.0 },

       {       0.0,        0.0,       1.0 },

       { -810728.0,  1403580.0,       0.0 }

       };

const double A2p0[3][3] = {

       {        0.0,        1.0,       0.0 },

       {        0.0,        0.0,       1.0 },

       { -1370589.0,        0.0,  527612.0 }

       };

const double A1p76[3][3] = {

       {      82758667.0, 1871391091.0, 4127413238.0 },

       {    3672831523.0,   69195019.0, 1871391091.0 },

       {    3672091415.0, 3528743235.0,   69195019.0 }

       };

const double A2p76[3][3] = {

       {    1511326704.0, 3759209742.0, 1610795712.0 },

       {    4292754251.0, 1511326704.0, 3889917532.0 },

       {    3859662829.0, 4292754251.0, 3708466080.0 }

       };

const double A1p127[3][3] = {

       {    2427906178.0, 3580155704.0,  949770784.0 },

       {     226153695.0, 1230515664.0, 3580155704.0 },

       {    1988835001.0,  986791581.0, 1230515664.0 }

       };

const double A2p127[3][3] = {

       {    1464411153.0,  277697599.0, 1610723613.0 },

       {      32183930.0, 1464411153.0, 1022607788.0 },

       {    2824425944.0,   32183930.0, 2093834863.0 }

       };

//-------------------------------------------------------------------------

// Return (a*s + c) MOD m; a, s, c and m must be < 2^35

//

double MultModM (double a, double s, double c, double m)

{

    double v;

    int32_t a1;

    v = a * s + c;

    if (v >= two53 || v <= -two53) {

        a1 = static_cast<int32_t> (a / two17);    a -= a1 * two17;

        v  = a1 * s;

        a1 = static_cast<int32_t> (v / m);     v -= a1 * m;

        v = v * two17 + a * s + c;

    }

    a1 = static_cast<int32_t> (v / m);

    /* in case v < 0)*/

    if ((v -= a1 * m) < 0.0) return v += m;   else return v;

}

//-------------------------------------------------------------------------

// Compute the vector v = A*s MOD m. Assume that -m < s[i] < m.

// Works also when v = s.

//

void MatVecModM (const double A[3][3], const double s[3], double v[3],

                 double m)

{

    int i;

    double x[3];               // Necessary if v = s

    for (i = 0; i < 3; ++i) {

        x[i] = MultModM (A[i][0], s[0], 0.0, m);

        x[i] = MultModM (A[i][1], s[1], x[i], m);

        x[i] = MultModM (A[i][2], s[2], x[i], m);

    }

    for (i = 0; i < 3; ++i)

        v[i] = x[i];

}

//-------------------------------------------------------------------------

// Compute the matrix C = A*B MOD m. Assume that -m < s[i] < m.

// Note: works also if A = C or B = C or A = B = C.

//

void MatMatModM (const double A[3][3], const double B[3][3],

                 double C[3][3], double m)

{

    int i, j;

    double V[3], W[3][3];

    for (i = 0; i < 3; ++i) {

        for (j = 0; j < 3; ++j)

            V[j] = B[j][i];

        MatVecModM (A, V, V, m);

        for (j = 0; j < 3; ++j)

            W[j][i] = V[j];

    }

    for (i = 0; i < 3; ++i)

        for (j = 0; j < 3; ++j)

            C[i][j] = W[i][j];

}

//-------------------------------------------------------------------------

// Compute the matrix B = (A^(2^e) Mod m);  works also if A = B. 

//

void MatTwoPowModM (const double A[3][3], double B[3][3], double m, int32_t e)

{

   int i, j;

   /* initialize: B = A */

   if (A != B) {

      for (i = 0; i < 3; ++i)

         for (j = 0; j < 3; ++j)

            B[i][j] = A[i][j];

   }

   /* Compute B = A^(2^e) mod m */

   for (i = 0; i < e; i++)

      MatMatModM (B, B, B, m);

}

//-------------------------------------------------------------------------

// Compute the matrix B = (A^n Mod m);  works even if A = B.

//

void MatPowModM (const double A[3][3], double B[3][3], double m, int32_t n)

{

    int i, j;

    double W[3][3];

    /* initialize: W = A; B = I */

    for (i = 0; i < 3; ++i)

        for (j = 0; j < 3; ++j) {

            W[i][j] = A[i][j];

            B[i][j] = 0.0;

        }

    for (j = 0; j < 3; ++j)

        B[j][j] = 1.0;

    /* Compute B = A^n mod m using the binary decomposition of n */

    while (n > 0) {

        if (n % 2) MatMatModM (W, B, B, m);

        MatMatModM (W, W, W, m);

        n /= 2;

    }

}

} // end of anonymous namespace

namespace ns3{

//-------------------------------------------------------------------------

// Generate the next random number.

//

double RngStream::U01 ()

{

    int32_t k;

    double p1, p2, u;

    /* Component 1 */

    p1 = a12 * Cg[1] - a13n * Cg[0];

    k = static_cast<int32_t> (p1 / m1);

    p1 -= k * m1;

    if (p1 < 0.0) p1 += m1;

    Cg[0] = Cg[1]; Cg[1] = Cg[2]; Cg[2] = p1;

    /* Component 2 */

    p2 = a21 * Cg[5] - a23n * Cg[3];

    k = static_cast<int32_t> (p2 / m2);

    p2 -= k * m2;

    if (p2 < 0.0) p2 += m2;

    Cg[3] = Cg[4]; Cg[4] = Cg[5]; Cg[5] = p2;

    /* Combination */

    u = ((p1 > p2) ? (p1 - p2) * norm : (p1 - p2 + m1) * norm);

    return (anti == false) ? u : (1 - u);

}

//-------------------------------------------------------------------------

// Generate the next random number with extended (53 bits) precision.

//

double RngStream::U01d ()

{

    double u;

    u = U01();

    if (anti) {

        // Don't forget that U01() returns 1 - u in the antithetic case

        u += (U01() - 1.0) * fact;

        return (u < 0.0) ? u + 1.0 : u;

    } else {

        u += U01() * fact;

        return (u < 1.0) ? u : (u - 1.0);

    }

}

//-------------------------------------------------------------------------

// Check that the seeds are legitimate values. Returns true if legal seeds,

// false otherwise.

//

bool RngStream::CheckSeed (const uint32_t seed[6])

{

    int i;

    for (i = 0; i < 3; ++i) {

        if (seed[i] >= m1) {

            cerr << "****************************************\n\n"

                 << "ERROR: Seed[" << i << "] >= 4294967087, Seed is not set."

                 << "\n\n****************************************\n\n";

            return (false);

        }

    }

    for (i = 3; i < 6; ++i) {

        if (seed[i] >= m2) {

	  cerr << "Seed[" << i << "] = " << seed[i] << endl; 

          cerr << "*****************************************\n\n"

               << "ERROR: Seed[" << i << "] >= 4294944443, Seed is not set."

               << "\n\n*****************************************\n\n";

          return (false);

        }

    }

    if (seed[0] == 0 && seed[1] == 0 && seed[2] == 0) {

         cerr << "****************************\n\n"

              << "ERROR: First 3 seeds = 0.\n\n"

              << "****************************\n\n";

         return (false);

    }

    if (seed[3] == 0 && seed[4] == 0 && seed[5] == 0) {

         cerr << "****************************\n\n"

              << "ERROR: Last 3 seeds = 0.\n\n"

              << "****************************\n\n";

         return (false);

    }

    return true;

}

//*************************************************************************

// Public members of the class start here

//-------------------------------------------------------------------------

// The default seed of the package; will be the seed of the first

// declared RngStream, unless SetPackageSeed is called.

//

double RngStream::nextSeed[6] =

{

   12345.0, 12345.0, 12345.0, 12345.0, 12345.0, 12345.0

};

//-------------------------------------------------------------------------

// constructor

//

RngStream::RngStream ()

{

   anti = false;

   incPrec = false;

   // Stream initialization moved to separate method.

}

RngStream::RngStream(const RngStream& r)

{

   anti = r.anti;

   incPrec = r.incPrec;

   for (int i = 0; i < 6; ++i) {

      Cg[i] = r.Cg[i];

      Bg[i] = r.Bg[i];

      Ig[i] = r.Ig[i];

   }

}

void RngStream::InitializeStream()

{ // Moved from the RngStream constructor above to allow seeding

  // AFTER the global package seed has been set in the Random

  // object constructor.

   /* Information on a stream. The arrays {Cg, Bg, Ig} contain the current

   state of the stream, the starting state of the current SubStream, and the

   starting state of the stream. This stream generates antithetic variates

   if anti = true. It also generates numbers with extended precision (53

   bits if machine follows IEEE 754 standard) if incPrec = true. nextSeed

   will be the seed of the next declared RngStream. */

   for (int i = 0; i < 6; ++i) {

      Bg[i] = Cg[i] = Ig[i] = nextSeed[i];

   }

   MatVecModM (A1p127, nextSeed, nextSeed, m1);

   MatVecModM (A2p127, &nextSeed[3], &nextSeed[3], m2);

}

//-------------------------------------------------------------------------

// Reset Stream to beginning of Stream.

//

void RngStream::ResetStartStream ()

{

   for (int i = 0; i < 6; ++i)

      Cg[i] = Bg[i] = Ig[i];

}

//-------------------------------------------------------------------------

// Reset Stream to beginning of SubStream.

//

void RngStream::ResetStartSubstream ()

{

   for (int i = 0; i < 6; ++i)

      Cg[i] = Bg[i];

}

//-------------------------------------------------------------------------

// Reset Stream to NextSubStream.

//

void RngStream::ResetNextSubstream ()

{

   MatVecModM(A1p76, Bg, Bg, m1);

   MatVecModM(A2p76, &Bg[3], &Bg[3], m2);

   for (int i = 0; i < 6; ++i)

       Cg[i] = Bg[i];

}

//-------------------------------------------------------------------------

// Reset Stream to Nth SubStream.

//

void RngStream::ResetNthSubstream (uint32_t N)

{

   if(N==0) return;

   for(uint32_t i=0;i<N;++i) {

      MatVecModM(A1p76, Bg, Bg, m1);

      MatVecModM(A2p76, &Bg[3], &Bg[3], m2);

   }

   for (int i = 0; i < 6; ++i)

       Cg[i] = Bg[i];

}

//-------------------------------------------------------------------------

bool RngStream::SetPackageSeed (const uint32_t seed[6])

{

  if (!CheckSeed (seed)) return false;

  for (int i = 0; i < 6; ++i)

    nextSeed[i] = seed[i];

  return true;

}

//-------------------------------------------------------------------------

bool RngStream::SetSeeds (const uint32_t seed[6])

{

  if (!CheckSeed (seed)) return false;

   for (int i = 0; i < 6; ++i)

      Cg[i] = Bg[i] = Ig[i] = seed[i];

   return true;

}

//-------------------------------------------------------------------------

// if e > 0, let n = 2^e + c;

// if e < 0, let n = -2^(-e) + c;

// if e = 0, let n = c.

// Jump n steps forward if n > 0, backwards if n < 0.

//

void RngStream::AdvanceState (int32_t e, int32_t c)

{

    double B1[3][3], C1[3][3], B2[3][3], C2[3][3];

    if (e > 0) {

        MatTwoPowModM (A1p0, B1, m1, e);

        MatTwoPowModM (A2p0, B2, m2, e);

    } else if (e < 0) {

        MatTwoPowModM (InvA1, B1, m1, -e);

        MatTwoPowModM (InvA2, B2, m2, -e);

    }

    if (c >= 0) {

        MatPowModM (A1p0, C1, m1, c);

        MatPowModM (A2p0, C2, m2, c);

    } else {

        MatPowModM (InvA1, C1, m1, -c);

        MatPowModM (InvA2, C2, m2, -c);

    }

    if (e) {

        MatMatModM (B1, C1, C1, m1);

        MatMatModM (B2, C2, C2, m2);

    }

    MatVecModM (C1, Cg, Cg, m1);

    MatVecModM (C2, &Cg[3], &Cg[3], m2);

}

//-------------------------------------------------------------------------

void RngStream::GetState (uint32_t seed[6]) const

{

   for (int i = 0; i < 6; ++i)

      seed[i] = static_cast<uint32_t> (Cg[i]);

}

//-------------------------------------------------------------------------

void RngStream::IncreasedPrecis (bool incp)

{

   incPrec = incp;

}

//-------------------------------------------------------------------------

void RngStream::SetAntithetic (bool a)

{

   anti = a;

}

//-------------------------------------------------------------------------

// Generate the next random number.

//

double RngStream::RandU01 ()

{

   if (incPrec)

      return U01d();

   else

      return U01();

}

//-------------------------------------------------------------------------

// Generate the next random integer.

//

int32_t RngStream::RandInt (int32_t low, int32_t high)

{

    return low + static_cast<int32_t> ((high - low + 1) * RandU01 ());

};

} //namespace ns3