/* zeta-pinning.c */
/* compile with:                                               */
/* MAC:   gcc -O6 -o zeta-pinning zeta-pinning.c           */
/* LINUX: gcc -O6 -o zeta-pinning zeta-pinning.c -lm       */

#include <math.h>
#include <stdio.h>
#include <stdlib.h>
/* #include <time.h> */
#include <unistd.h> /* For getopt */


/* external references for getopt */
extern char *optarg;
extern int optind;
extern int optopt;
extern int opterr;
extern int optreset;


/*--------------------------------------------------------------------------*/
/* Random Numbers Generators (see at the end of the source)                 */
/*--------------------------------------------------------------------------*/
/* ran_array */
extern double *ranf_arr_ptr;
#define ranf_arr_next() (*ranf_arr_ptr>=0? *ranf_arr_ptr++: ranf_arr_cycle())
double ranf_arr_cycle();
void ranf_start(long seed);
/* mt19937 */
void init_genrand(unsigned long s);
double genrand_real1(void);
double genrand_real3(void);
/*--------------------------------------------------------------------------*/

enum {
  ra,   /* ran_array */
  mt    /* mersenne-twister */
} generator = mt; /* default generator */
 
int save_rng_state(char *name);
int load_rng_state(char *name);
void init_rng_state(unsigned long seed);
double get_rng_double();
double ranu();


double *z1,*z2,*zaux,*omega;
double lambda = 0.6;
double h = 0.43;
int N;
int step;
int each = 1;

int feach = 0;
int fsel = 0;

#define NOUTDIM 100
int nout[NOUTDIM];
int nout_count = 0;

long seed = 31416;
char omegafile[256];
char saveomegafile[256];
char load_zeta_state[256] = "zeta-pinning.stt";
char save_zeta_state[256] = "zeta-pinning.stt";

/* Flags */
int ffile = 0;  
int fseed = 0;
int fsaverng = 0;
int fsize =0;
int flambda =0;
int fh = 0;
int fsaveomega = 0;
int finvert = 0;
int fstep = 0;
int fsave_zeta_state = 0;
int fload_zeta_state = 0;
int fG = 0;



/* Functions used to limit to "cut" some RW trajectories */

#define LOW 6  
#define HIGH 6

#define TILL 1000

//double tlow = 1.0 * (TILL * TILL) / (LOW * LOW) ;    /* Does nothing till */
//double thigh = 1.0 * (TILL * TILL) / (HIGH * HIGH) ; /* N <= TILL         */

int cut_low(int N) 
{
  int c;
  if (N <= TILL) c = N;
  else if (TILL > (c = LOW * sqrt(N))) c = TILL;
  else if (N < c) c = N;
  //  if (N < (c = LOW * sqrt(N + tlow - TILL))) c = N;
  return c;
}

int cut_high(int N)
{
  int c;
  if (N <= TILL) c = N;
  else if (TILL > (c = HIGH * sqrt(N))) c = TILL;
  else if (N < c) c = N;
  //  if (N < (c = HIGH * sqrt(N + thigh - TILL))) c = N;
  return c;
}



/* Usage */

void usage()
{
  fprintf(stderr,"\n\
 zeta-pinning [options]\n\n\
  [Parameters of the polymer]\n\
     -n<size>         final size of the system (int)\n\
     -l<lambda>       lambda (double) - default value is 0.6\n\
     -h<h>            h (double) - default value is 0.43\n\
 \n\
  [Output saving options]\n\
     -e<out_step>     print one line of output each <out_step> (int)\n\
                      - default value is 1 (= print every line)\n\
     -t<out_size>     print results for the size <out_size>\n\
  (The -t option can be repeated to print various intermediate sizes, -e and\n\
  -t options are mutually exclusive)\n\
 \n\
  [Random environment]\n\
     -f<omega_file>   load sequence of omegas from file <omegafile>\n\
     -r<seed>         seed for initializing RNG (long int)\n\
     -g<type>         generator (0: ran_array, 1: mersenne-twiser)\n\
     -G               generate gaussian omegas\n\
 \n\
  (Precedency rules: If option '-f' is chosen, the environment is loaded\n\
  from file <omega_file>, otherwise the environment is generated by the RNG.\n\
  If seed is given, RNG is initialized from that; else, if file 'zeta-pinning.rng'\n\
  is found in folder, RNG state is automatically restored from that; else,\n\
  RNG is initialized by default with seed 31416)\n\
 \n\
     -i               use omega in the reverse order\n\
     -z<state_file>   save sequence of omegas to file <statefile>\n\
     -w               save RNG state to file 'zeta-pinning.rng' (overwrite!)\n\
 \n\
  [Recovery options]\n\
     -a               load zeta state from file 'zeta-pinning.stt'\n\
     -b               save zeta state to file 'zeta-pinning.stt' (overwrite!)\n\
     -c<save_step>    save zeta state each <save_step> steps - default\n\
                      value is <size>\n\
 \n\
     -?               usage\n\n\
 The program send output to stdout and control messages to stderr.\n\
 Output is made of a sequence of lines with the following format:\n\
  <size> <incr> <omegasum> <zeta> <zeta0>\n\
 where:\n\
   <size>     system size\n\
   <incr>     sum of omegas since the last output\n\
   <omegasum> overall sum of omegas\n\
   <zeta>     value of the partition sum\n\
   <zeta0>    partition sum when the polymer is conditioned to return to 0.\n");
}



/* Parse arguments */

void parse_arguments(int argc, char **argv)
{
  int ch;
  int xx;

  while ((ch = getopt(argc, argv, "g:in:l:h:f:r:wz:abc:e:Gt:?")) != -1)
    switch (ch) {

    case 'i':
      finvert = 1;
      break;

    case 'G':
      fG = 1;
      break;

    case 'w':
      fsaverng = 1;
      break;


    case 'g':
      
      if (1!=sscanf(optarg,"%d",&xx))
	{
	  fprintf(stderr,"\nError on argument of -n<size>. Exit.\n\n");
	  exit(-1);
	} else {if (xx==0) {generator = ra;} else if (xx==1) {generator = mt;} 
	else {fprintf(stderr,"\nError on argument of -g<type>. Exit.\n\n");
	  exit(-1);}}
      break;

    case 'n':
      fsize = 1;
      if (1!=sscanf(optarg,"%d",&N))
	{
	  fprintf(stderr,"\nError on argument of -n<size>. Exit.\n\n");
	  exit(-1);
	}
      break;

    case 'l':
      if (1!=sscanf(optarg,"%lf",&lambda))
	{
	  fprintf(stderr,"\nError on argument of -l<lambda>. Exit.\n\n");
	  exit(-1);
	}
      flambda = 1;
      break;

    case 'h':
      if (1!=sscanf(optarg,"%lf",&h))
	{
	  fprintf(stderr,"\nError on argument of -h<h>. Exit.\n\n");
	  exit(-1);
	}
      fh = 1;
      break;

    case 'r':
      fseed = 1;
      if (1!=sscanf(optarg,"%ld",&seed))
	{
	  fprintf(stderr,"\nError on argument of -r<seed>. Exit.\n\n");
	  exit(-1);
	}
      break;

    case 'f':
      ffile = 1;
      if (1!=sscanf(optarg,"%s",&omegafile))
	{
	  fprintf(stderr,"\nError on argument of -f<omegafile>. Exit.\n\n");
	  exit(-1);
	}
      break;

    case 'z':
      fsaveomega = 1;
      if (1!=sscanf(optarg,"%s",&saveomegafile))
	{
	  fprintf(stderr,"\nError on argument of -z<omegafile>. Exit.\n\n");
	  exit(-1);
	}
      break;

    case 'a':
      fload_zeta_state = 1;
      break;

    case 'b':
      fsave_zeta_state = 1;
      break;

    case 'c':
      if (1!=sscanf(optarg,"%d",&step))
	{
	  fprintf(stderr,"\nError on argument of -c<step>. Exit.\n\n");
	  exit(-1);
	}
      fstep = 1;
      break;

    case 'e':
      if (fsel) {
	fprintf(stderr,"\nYou cannot specify both -e and -t flags.\n\n");
	exit(-1);
      }
      if (1!=sscanf(optarg,"%d",&each))
	{
	  fprintf(stderr,"\nError on argument of -e<each>. Exit.\n\n");
	  exit(-1);
	} else feach = 1;
      break;


    case 't':
      if (feach) {
	fprintf(stderr,"\nYou cannot specify both -e and -t flags.\n\n");
	exit(-1);
      }
      {
	int aux;
	if ((1!=sscanf(optarg,"%d",&aux))||(aux<0))
	  {
	    fprintf(stderr,"\nError on argument of -t<out_size>. Exit.\n\n");
	    exit(-1);
	  } else {
	  if (nout_count == NOUTDIM) {
	    fprintf(stderr,"\nToo many -t flags. Exit.\n\n");
	    exit(-1);
	  }
	  nout[nout_count++] = aux;
	  fsel = 1;
	}
      }
      break;

    case '?':
    default:
      usage();
      exit(-1);
      break;
    }

  argc -= optind;
  argv += optind;

  if (!fsize)
    {
      fprintf(stderr,"\nYou must provide at least the final size of the system.\n");
      usage();
      exit(-1);
    }

  if (!fstep)
    step = N;

  if (ffile && fsaverng)
    {
      fprintf(stderr,"\nOptions '-f<omega_file>' and '-w' cannot be used together.\n\n");
      exit(-1);
    }

}



/* Function used in the sampling loop */

double next_alpha(int i)
{
  double alpha;
  alpha = exp(lambda*omega[i] - h);
  return alpha;
}



/* Main */

int main(int argc, char **argv)
{
  int i,j,k;
  
  parse_arguments(argc,argv);

#if 0
  fprintf(stderr,"\n%f\t%f\t%d\t%d\n\n",tlow,thigh,cut_low(N),cut_high(N));
  return 0;
#endif

  if (!flambda)
    {
      fprintf(stderr,"\nWarning: value of lambda not given, setted by default to %f", lambda);
    }

  if (!fh)
    {
      fprintf(stderr,"\nWarning: value of h not given, setted by default to %f", h);
    }

  fprintf(stderr,"\nN=%d  lambda=%f  h=%f\n\n",N,lambda,h);

  omega = (double*)malloc(sizeof(double)*N);

  if(!ffile)
    {
      if (fseed)
	{
	  fprintf(stderr,"RNG initialized with seed: %ld\n\n",seed);
	  init_rng_state(seed);
	}
      else
	{
	  if (!load_rng_state("zeta-pinning.rng"))
	    {
	      init_rng_state(seed);
	      fprintf(stderr,"Warning: RNG initialized by default with seed '%ld'\n\n",seed);
	    }
	  else fprintf(stderr,"RNG restored from file 'zeta-pinning.rng'\n\n");
	}
    }


  if (generator == ra)
    {
      fprintf(stderr,"RNG: unsing ran_array\n");

    } else if (generator == mt)
    {
      fprintf(stderr,"RNG: unsing Mersenne-Twister\n");

    }



  if (ffile) 
    {
      /* Load random environment */

      fprintf(stderr,"Loading omega from '%s' ... ",omegafile);

      FILE *stream = fopen(omegafile,"r");
      
      if (ferror(stream)) {
	fprintf(stderr,"\nProblems opening file '%s'. Exit.\n\n",omegafile);
	exit(-1);
      }
      
      for(i=0; i< N; i++) {
	double a;
	if (1!=fscanf(stream,"%lf",&a))
	  {
	    fprintf(stderr,"\nError reading file '%s'. Exit.\n\n",omegafile);
	    exit(-1);
	  }
	else { omega[i] = a; }
      }

      fclose(stream);

      fprintf(stderr,"OK\n\n");
    }
  else 
    {
      /* Generate a random environment */

      if (fG == 0) {
      
	fprintf(stderr,"Generating random omegas ... ");

	double aaa = get_rng_double(); /* To skip the first omega generated */
	                               /* (backward compatibility...)       */
	for(i=0; i< N; i++) {
	  double a = get_rng_double();
	  if ((0 <= a) && (a < 0.5)) omega[i] = -1;
	  else if (a <= 1) omega[i] = 1;		
	  else {fprintf(stderr,"\nProblems with the RNG. Exit.\n\n"); exit(-1);}
	}

	fprintf(stderr,"OK\n\n");

      } else {      /* Gaussian case */

	fprintf(stderr,"Generating GAUSSIAN random omegas ... ");

	for(i=0; i<(N/2); i++) {
	  
	  double x1, x2, w, y1, y2;
	  
	  do {
	    x1 = 2.0 * ranu() - 1.0;
	    x2 = 2.0 * ranu() - 1.0;
	    w = x1 * x1 + x2 * x2;
	  } while ( w >= 1.0 );
	  
	  w = sqrt( (-2.0 * log( w ) ) / w );
	  y1 = x1 * w;
	  y2 = x2 * w;

	  omega[2*i] = y1;
	  omega[2*i+1] = y2;
	}
	
	fprintf(stderr,"OK\n\n");
      
      }
    }


  if (finvert)   fprintf(stderr,"Using omega in reverse order\n\n");


  if (fsaveomega) {
    
    /* Save random environment */

    if (!finvert)
      fprintf(stderr,"Saving omega in '%s' ... ",saveomegafile);
    else
      fprintf(stderr,"Saving omega (in reverse order) in '%s' ... ",saveomegafile);

    FILE *stream = fopen(saveomegafile,"w");
    
    if (ferror(stream)) {
      fprintf(stderr,"\nProblems opening file '%s': skipping omega saving.\n\n",saveomegafile);
    }
    else {
      for(i=0; i< N; i++) {
	double a = finvert ? omega[N-1-i] : omega[i] ;
	fprintf(stream,"%f\n",a);
      }

      fclose(stream);
    
      fprintf(stderr,"OK\n\n");
    }
  }


  if (fsaverng) 
    {
      fprintf(stderr,"Saving RNG state ... ");
      if (save_rng_state("zeta-pinning.rng")) fprintf(stderr,"OK\n\n");
    }
 

  int sstart;
  sstart = cut_low(N);

  int sstop;
  sstop = cut_high(N);

  int maxlength; /* To determine the length of vectors z1, z2 */
  maxlength = sstart + sstop + 1;


  /* Alloc (+2 is for boundary conditions) */
  z1 = (double*)malloc(sizeof(double)*(maxlength + 2)) + 1 + sstart;
  z2 = (double*)malloc(sizeof(double)*(maxlength + 2)) + 1 + sstart;
  /* Observe that "+ 1 + start" is given in order that z[j] at step k */
  /* correspond to Z_{2k}(2j), where k = 0, 1, 2, ... and             */
  /* j = -cut_low(k), ..., -1, 0, +1, ..., +cut_high(k)               */

  int NN;
  double llambda, hh, oomegasum;


  /* Load zeta state */

  if (fload_zeta_state) 
    {
      fprintf(stderr,"Loading zeta state from '%s'\n",load_zeta_state);
    
      FILE *stream = fopen(load_zeta_state,"r");
    
      if (ferror(stream))
	{
	  fprintf(stderr,"\nProblems opening file '%s'. Exit.\n\n",load_zeta_state);
	  exit(-1);
	}

      /* The first line of the file must contain Nstart, lambda, h, omegasum */

      if (1!=fscanf(stream,"%d",&NN))
	{
	  fprintf(stderr,"\nError reading first line of '%s'. Exit.\n\n",load_zeta_state);
	  exit(-1);
	}

      if (1!=fscanf(stream,"%lf",&llambda))
	{
	  fprintf(stderr,"\nError reading first line of '%s'. Exit.\n\n",load_zeta_state);
	  exit(-1);
	}

      if (1!=fscanf(stream,"%lf",&hh))
	{
	  fprintf(stderr,"\nError reading first line of '%s'. Exit.\n\n",load_zeta_state);
	  exit(-1);
	}

      if (1!=fscanf(stream,"%le",&oomegasum))
	{
	  fprintf(stderr,"\nError reading first line of '%s'. Exit.\n\n",load_zeta_state);
	  exit(-1);
	}

      fprintf(stderr,"From file '%s' I read the values:\nNstart=%d, lambda=%f, h=%f, omegasum=%le\n"
	      ,load_zeta_state,NN,llambda,hh,oomegasum);

      if (NN >= N)
	{
	  fprintf(stderr,"\nThe value of Nstart (=%d) I read from '%s' is not"
		  " smaller than the one you gave (=%d). Exit.\n\n"
		  ,NN,load_zeta_state,N);
	  exit(-1);
	}


      if (lambda != llambda) 
	{
	  fprintf(stderr,"\nThe value of lambda (=%f) I read from '%s' does not"
		  " coincide with the one you gave (=%f). Exit.\n\n",
		  llambda,load_zeta_state,lambda);
	  exit(-1);
	}
	
      if (h != hh) 
	{
	  fprintf(stderr,"\nThe value of h (=%f) I read from '%s' does not"
		  " coincide with the one you gave (=%f). Exit.\n\n",
		  hh,load_zeta_state,h);
	  exit(-1);
	} 
	

      /* Copy zeta state into z1 and z2 */

      int tstart;
      tstart = cut_low(NN);

      int tstop;
      tstop = cut_high(NN);	
	
      for (i=-sstart -1; i< -tstart; i++) { /* '-1' is for bound. cond. */
	z2[i] = z1[i] = 0.0;
      }

      for (i= tstop + 1 ; i<= sstop +1; i++) { /* '+1' is for bound. cond. */
	z2[i] = z1[i] = 0.0;
      }

      double a;
      int bb;
	
      for(i= - tstart; i <= + tstop; i++) {
	if ((1!=fscanf(stream,"%d",&bb)) || (bb != i) )
	  {
	    fprintf(stderr,"\nError reading file '%s' at \"line\" %d. Exit.\n\n",
		    load_zeta_state, i);
	    exit(-1);
	  }
	if (1!=fscanf(stream,"%le",&a))
	  {
	    fprintf(stderr,"\nError reading file '%s' at \"line\" %d. Exit.\n\n",
		    load_zeta_state, i);
	    exit(-1);
	  }
	else { z2[i] = z1[i] = a; }
      }

      fprintf(stderr,"Zeta state loaded and restored.\n\n");

      fclose(stream);

    }
    

  /* Standard initialization (remember boundary components) */

  if(!fload_zeta_state)
    {
      for(i=-sstart - 1; i<= sstop + 1; i++) z2[i] = z1[i] = 0.0;
      z1[0] = 1.0; 
    }

  
  
  /*---------------*/
  /* Sampling loop */
  /*---------------*/
  {

    int start, stop, iii;
    double alpha;
    double ff, omegasum, incr;

    omegasum = ( (fload_zeta_state) ? oomegasum : 0.0 );
    incr = 0.0;

    for(i=( (fload_zeta_state) ? (NN + 1) : 1 ); i<= N; i++) {

      iii = (finvert ? N-i+1 : i) -1;

      alpha = next_alpha(iii);

      start = cut_low(i);

      stop = cut_high(i);
      
      ff = 0.0; /* Reinitialize ff at each step */
      

      for(j= -start; j< 0; j++) {
	ff += z2[j] = 0.25*(z1[j+1]+2*z1[j]+z1[j-1]);
      }

      //      ff += z2[-1] = 0.25*(z1[0]+2*z1[-1]+z1[-2]);
      ff += z2[0] = 0.25*alpha*(z1[1]+2*z1[0]+z1[-1]);
      //      ff += z2[1] = 0.25*(z1[0]+2*z1[1]+z1[2]);

      for(j= 1; j<= stop; j++) {
	ff += z2[j] = 0.25*(z1[j+1]+2*z1[j]+z1[j-1]);
      }
      

      omegasum += omega[iii];

      incr += omega[iii];
      
      /* Swap vectors */
      zaux = z1; z1 = z2; z2 = zaux;
      
      /* Write output */
      if (fsel) {
	int ii;
	for(ii=0; ii<nout_count; ii++) if (nout[ii]==i) {
	  {
	    printf("%d\t%3.1f\t%le\t%le\t%le\n",i,incr,omegasum,ff,z1[0]);
	    incr = 0.0;
	  }
	  break;
	}
      }
      else {
	if (i % each == 0)
	  {
	    printf("%d\t%3.1f\t%le\t%le\t%le\n",i,incr,omegasum,ff,z1[0]);
	    incr = 0.0;
	  }
      }

      /* Save zeta state */
      if((fsave_zeta_state) && (i%step == 0)) {

	fprintf(stderr,"Saving zeta state for N = %d ... ",i);
	
	FILE *stream = fopen(save_zeta_state,"w");
    
	if (ferror(stream)) {
	  fprintf(stderr,"\nProblems opening file '%s': cannot save zeta state\n",save_zeta_state);
	}
	else {
	  fprintf(stream,"%d\t%f\t%f\t%le\n",i,lambda,h,omegasum);

	  for(k= -start ; k<= stop; k++) {
	    fprintf(stream,"%d\t%.20le\n", k, z1[k]);
	  }

	  fprintf(stream,"Z(x) for x from -%d to %d\n",start,stop);
	  
	  fprintf(stderr,"OK\n\n");
	  
	  fclose(stream);
	}
      }

    }

     fflush(stdout);  /* flush the output buffer */
 
  }
  
  fprintf(stderr,"\n-Done-\n\n");

  return 0;
}




/*--------------------------------------------------------------------------*/
/* Random Numbers Generators                                                */
/*--------------------------------------------------------------------------*/


/*--------------------------------------------------------------------------*/
/* ran_array */
extern double *ranf_arr_ptr;
#define ranf_arr_next() (*ranf_arr_ptr>=0? *ranf_arr_ptr++: ranf_arr_cycle())
double ranf_arr_cycle();
void ranf_start(long seed);
/* mt19937 */
void init_genrand(unsigned long s);
double genrand_real1(void);
/*--------------------------------------------------------------------------*/

void init_rng_state(unsigned long seed)
{
  /* initalize the generators with the same seed */
  ranf_start(seed);
  init_genrand(seed);
}

double get_rng_double()
{
  if (generator == ra) 
    {
      return ranf_arr_next();
    }
  else
    {
      return genrand_real1();
    }
}

double ranu()
{
  if (generator == ra) 
    {
      return ranf_arr_next();
    }
  else
    {
      return genrand_real3();
    }
}



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


/*    This program by D E Knuth is in the public domain and freely copyable
 *    AS LONG AS YOU MAKE ABSOLUTELY NO CHANGES!
 *    It is explained in Seminumerical Algorithms, 3rd edition, Section 3.6
 *    (or in the errata to the 2nd edition --- see
 *        http://www-cs-faculty.stanford.edu/~knuth/taocp.html
 *    in the changes to Volume 2 on pages 171 and following).              */

/*    N.B. The MODIFICATIONS introduced in the 9th printing (2002) are
      included here; there's no backwards compatibility with the original. */

/*    If you find any bugs, please report them immediately to
 *                 taocp@cs.stanford.edu
 *    (and you will be rewarded if the bug is genuine). Thanks!            */

/************ see the book for explanations and caveats! *******************/
/************ in particular, you need two's complement arithmetic **********/

#define KK 100                     /* the long lag */
#define LL  37                     /* the short lag */
#define mod_sum(x,y) (((x)+(y))-(int)((x)+(y)))   /* (x+y) mod 1.0 */

double ran_u[KK];           /* the generator state */

#ifdef __STDC__
void ranf_array(double aa[], int n)
#else
     void ranf_array(aa,n)    /* put n new random fractions in aa */
     double *aa;   /* destination */
     int n;      /* array length (must be at least KK) */
#endif
{
  register int i,j;
  for (j=0;j<KK;j++) aa[j]=ran_u[j];
  for (;j<n;j++) aa[j]=mod_sum(aa[j-KK],aa[j-LL]);
  for (i=0;i<LL;i++,j++) ran_u[i]=mod_sum(aa[j-KK],aa[j-LL]);
  for (;i<KK;i++,j++) ran_u[i]=mod_sum(aa[j-KK],ran_u[i-LL]);
}

/* the following routines are adapted from exercise 3.6--15 */
/* after calling ranf_start, get new randoms by, e.g., "x=ranf_arr_next()" */

#define QUALITY 1009 /* recommended quality level for high-res use */
double ranf_arr_buf[QUALITY];
double ranf_arr_sentinel=-1.0;
double *ranf_arr_ptr=&ranf_arr_sentinel; /* the next random fraction, or -1 */

#define ranf_arr_next() (*ranf_arr_ptr>=0? *ranf_arr_ptr++: ranf_arr_cycle())
double ranf_arr_cycle()
{
  ranf_array(ranf_arr_buf,QUALITY);
  ranf_arr_buf[100]=-1;
  ranf_arr_ptr=ranf_arr_buf+1;
  return ranf_arr_buf[0];
}

#define TT  70   /* guaranteed separation between streams */
#define is_odd(s) ((s)&1)

#ifdef __STDC__
void ranf_start(long seed)
#else
     void ranf_start(seed)    /* do this before using ranf_array */
     long seed;            /* selector for different streams */
#endif
{
  register int t,s,j;
  double u[KK+KK-1];
  double ulp=(1.0/(1L<<30))/(1L<<22);               /* 2 to the -52 */
  double ss=2.0*ulp*((seed&0x3fffffff)+2);
	
  for (j=0;j<KK;j++) {
    u[j]=ss;                                /* bootstrap the buffer */
    ss+=ss; if (ss>=1.0) ss-=1.0-2*ulp;  /* cyclic shift of 51 bits */
  }
  u[1]+=ulp;                     /* make u[1] (and only u[1]) "odd" */
  for (s=seed&0x3fffffff,t=TT-1; t; ) {
    for (j=KK-1;j>0;j--)
      u[j+j]=u[j],u[j+j-1]=0.0;                         /* "square" */
    for (j=KK+KK-2;j>=KK;j--) {
      u[j-(KK-LL)]=mod_sum(u[j-(KK-LL)],u[j]);
      u[j-KK]=mod_sum(u[j-KK],u[j]);
    }
    if (is_odd(s)) {                             /* "multiply by z" */
      for (j=KK;j>0;j--) u[j]=u[j-1];
      u[0]=u[KK];                    /* shift the buffer cyclically */
      u[LL]=mod_sum(u[LL],u[KK]);
    }
    if (s) s>>=1; else t--;
  }
  for (j=0;j<LL;j++) ran_u[j+KK-LL]=u[j];
  for (;j<KK;j++) ran_u[j-LL]=u[j];
  for (j=0;j<10;j++) ranf_array(u,KK+KK-1);  /* warm things up */
  ranf_arr_ptr=&ranf_arr_sentinel;
}


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



/* Mersenne-Twister */

/* 
   A C-program for MT19937, with initialization improved 2002/2/10.
   Coded by Takuji Nishimura and Makoto Matsumoto.
   This is a faster version by taking Shawn Cokus's optimization,
   Matthe Bellew's simplification, Isaku Wada's real version.

   Before using, initialize the state by using init_genrand(seed) 
   or init_by_array(init_key, key_length).

   Copyright (C) 1997 - 2002, Makoto Matsumoto and Takuji Nishimura,
   All rights reserved.                          

   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions
   are met:

   1. Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.

   2. Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions and the following disclaimer in the
   documentation and/or other materials provided with the distribution.

   3. The names of its contributors may not be used to endorse or promote 
   products derived from this software without specific prior written 
   permission.

   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
   CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
   EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
   PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
   PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
   LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
   NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
   SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.


   Any feedback is very welcome.
   http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html
   email: m-mat @ math.sci.hiroshima-u.ac.jp (remove space)
*/



/* Period parameters */  
#define N 624
#define M 397
#define MATRIX_A 0x9908b0dfUL   /* constant vector a */
#define UMASK 0x80000000UL /* most significant w-r bits */
#define LMASK 0x7fffffffUL /* least significant r bits */
#define MIXBITS(u,v) ( ((u) & UMASK) | ((v) & LMASK) )
#define TWIST(u,v) ((MIXBITS(u,v) >> 1) ^ ((v)&1UL ? MATRIX_A : 0UL))

static unsigned long state[N]; /* the array for the state vector  */
static int left = 1;
static int initf = 0;
static unsigned long *next;

/* initializes state[N] with a seed */
void init_genrand(unsigned long s)
{
  int j;
  state[0]= s & 0xffffffffUL;
  for (j=1; j<N; j++) {
    state[j] = (1812433253UL * (state[j-1] ^ (state[j-1] >> 30)) + j); 
    /* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */
    /* In the previous versions, MSBs of the seed affect   */
    /* only MSBs of the array state[].                        */
    /* 2002/01/09 modified by Makoto Matsumoto             */
    state[j] &= 0xffffffffUL;  /* for >32 bit machines */
  }
  left = 1; initf = 1;
}

/* initialize by an array with array-length */
/* init_key is the array for initializing keys */
/* key_length is its length */
/* slight change for C++, 2004/2/26 */
void init_by_array(unsigned long init_key[], int key_length)
{
  int i, j, k;
  init_genrand(19650218UL);
  i=1; j=0;
  k = (N>key_length ? N : key_length);
  for (; k; k--) {
    state[i] = (state[i] ^ ((state[i-1] ^ (state[i-1] >> 30)) * 1664525UL))
      + init_key[j] + j; /* non linear */
    state[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
    i++; j++;
    if (i>=N) { state[0] = state[N-1]; i=1; }
    if (j>=key_length) j=0;
  }
  for (k=N-1; k; k--) {
    state[i] = (state[i] ^ ((state[i-1] ^ (state[i-1] >> 30)) * 1566083941UL))
      - i; /* non linear */
    state[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
    i++;
    if (i>=N) { state[0] = state[N-1]; i=1; }
  }

  state[0] = 0x80000000UL; /* MSB is 1; assuring non-zero initial array */ 
  left = 1; initf = 1;
}

static void next_state(void)
{
  unsigned long *p=state;
  int j;

  /* if init_genrand() has not been called, */
  /* a default initial seed is used         */
  if (initf==0) init_genrand(5489UL);

  left = N;
  next = state;
    
  for (j=N-M+1; --j; p++) 
    *p = p[M] ^ TWIST(p[0], p[1]);

  for (j=M; --j; p++) 
    *p = p[M-N] ^ TWIST(p[0], p[1]);

  *p = p[M-N] ^ TWIST(p[0], state[0]);
}

/* generates a random number on [0,0xffffffff]-interval */
unsigned long genrand_int32(void)
{
  unsigned long y;

  if (--left == 0) next_state();
  y = *next++;

  /* Tempering */
  y ^= (y >> 11);
  y ^= (y << 7) & 0x9d2c5680UL;
  y ^= (y << 15) & 0xefc60000UL;
  y ^= (y >> 18);

  return y;
}

/* generates a random number on [0,0x7fffffff]-interval */
long genrand_int31(void)
{
  unsigned long y;

  if (--left == 0) next_state();
  y = *next++;

  /* Tempering */
  y ^= (y >> 11);
  y ^= (y << 7) & 0x9d2c5680UL;
  y ^= (y << 15) & 0xefc60000UL;
  y ^= (y >> 18);

  return (long)(y>>1);
}

/* generates a random number on [0,1]-real-interval */
double genrand_real1(void)
{
  unsigned long y;

  if (--left == 0) next_state();
  y = *next++;

  /* Tempering */
  y ^= (y >> 11);
  y ^= (y << 7) & 0x9d2c5680UL;
  y ^= (y << 15) & 0xefc60000UL;
  y ^= (y >> 18);

  return (double)y * (1.0/4294967295.0); 
  /* divided by 2^32-1 */ 
}

/* generates a random number on [0,1)-real-interval */
double genrand_real2(void)
{
  unsigned long y;

  if (--left == 0) next_state();
  y = *next++;

  /* Tempering */
  y ^= (y >> 11);
  y ^= (y << 7) & 0x9d2c5680UL;
  y ^= (y << 15) & 0xefc60000UL;
  y ^= (y >> 18);

  return (double)y * (1.0/4294967296.0); 
  /* divided by 2^32 */
}

/* generates a random number on (0,1)-real-interval */
double genrand_real3(void)
{
  unsigned long y;

  if (--left == 0) next_state();
  y = *next++;

  /* Tempering */
  y ^= (y >> 11);
  y ^= (y << 7) & 0x9d2c5680UL;
  y ^= (y << 15) & 0xefc60000UL;
  y ^= (y >> 18);

  return ((double)y + 0.5) * (1.0/4294967296.0); 
  /* divided by 2^32 */
}

/* generates a random number on [0,1) with 53-bit resolution*/
double genrand_res53(void) 
{ 
  unsigned long a=genrand_int32()>>5, b=genrand_int32()>>6; 
  return(a*67108864.0+b)*(1.0/9007199254740992.0); 
} 
/* These real versions are due to Isaku Wada, 2002/01/09 added */


/*--------------------------------------------------------------------------*/
/*--------------------------------------------------------------------------*/



/* Save and restore generator state */

int save_rng_state(char *name)
{
  FILE *stream = fopen(name,"w");
  int i;
  if (ferror(stream)) {
    fprintf(stderr,"Problems writing in file '%s'\n\n",name);
    return 0;
  }
  if (generator == ra) {
    fprintf(stream,"type=%d\n",0); // identifier
    for(i=0; i< KK; i++) 	fprintf(stream,"%lf\n",ran_u[i]);

    ranf_arr_cycle(); // refill the buffer

  } 
  else {
    fprintf(stream,"type=%d\n",1); // identifier
    for(i=0; i< N; i++) 	fprintf(stream,"%lu\n",state[i]);
    next_state(); // refill the buffer
  }
  fclose(stream);


  return 1;
}

int load_rng_state(char *name)
{
  FILE *stream = fopen(name,"r");
  int i;
  
  if ((!stream)||ferror(stream)) {
    fprintf(stderr,"Problems reading file '%s'\n\n",name);
    return 0;
  }
  int type;

  if (1!=fscanf(stream,"type=%ld\n",&type))
    {
      fprintf(stderr,"Problems reading generator type for file '%s'\n\n",name);
      return 0;
    }

  if (type == 0) {
    /*fprintf(stderr,"reading ran_array state\n");*/
    double buffer[KK];
    for(i=0; i< KK; i++) 	{
      double a;
      if (1!=fscanf(stream,"%lf\n",&(buffer[i])))
	{
	  fprintf(stderr,"Problems reading file '%s'\n\n",name);
	  return 0;
	}
    }

    for(i=0; i< KK; i++) ran_u[i] = buffer[i];
    ranf_arr_cycle();
    generator = ra;
  } 
  else if (type == 1)
    {
      unsigned long buffer[N];
      /*fprintf(stderr,"reading mersenne-twister state\n");*/
      for(i=0; i< N; i++) 	{
	unsigned long a;
	if (1!=fscanf(stream,"%lu\n",&(buffer[i])))
	  {
	    fprintf(stderr,"Problems reading file '%s'\n\n",name);
	    return 0;
	  }
      }

      for(i=0; i< N; i++) state[i] = buffer[i];
      initf =1;
      next_state(); // refill the buffer
      generator = mt;
    }
  else {
    fprintf(stderr,"Unknown generator type in file '%s'\n\n",name);
    return 0;
  }
  fclose(stream);

  return 1;
}


/*--------------------------------------------------------------------------*/
/*--------------------------------------------------------------------------*/