int TightenWindows (long NO_JOBS, long *release, long *due, long *proc_time, long *dlist) {

  short FLAG, INF, CHNG, ROUNDS;
  long i, j, k, t, head;
  long release2[MAXJOBS+1], due2[MAXJOBS+1];
  long sindex[MAXJOBS+1];
  long P, H, C, CI[MAXJOBS];

  for(i=0; i<=NO_JOBS; i++)   sindex[i]=i;
  for(i=0; i<=NO_JOBS; i++)   CI[i]=0;  
  INF=0;
  CHNG=0;

  //cout << "dlist = " ;
  //for(i=0; i<=14; i++) cout << " " << dlist[i] ;
  //cout << endl;

  /* 1.1. Read precedence constraints from array in the format of the file*/
  FLAG=1;
  head=dlist[0];
  i=1;
  while(FLAG>=0) {
    if (dlist[i]>0) {
      delay[dlist[i]][head]=dlist[i+1];
      i=i+2;
    }
    else if (dlist[i]==0 && dlist[i+1]>0) {
      head=dlist[i+1];
      i=i+2;
    }
    else if (dlist[i]==0 && dlist[i+1]==0) {
      FLAG=-1;
    }
  }

  /* 1.2. Convert end of time windows to due times ------------------------- */
  for (i=1; i<=NO_JOBS; i++) due += proc_time[i];

  /* 1.3. Print-out imported data; this part will be deleted when integrated */
  //cout << "Release, Due and Processing Times" << endl;
  //for(i=1; i<=NO_JOBS; i++) cout <<"  "<<i <<">  r="<<release[i]<<"  d="<<due[i]<< "  p="<<proc_time[i]<<endl;
  //cout << "Delayed Precedence Constraints (DPCs)" << endl;
  for(i=1; i<=NO_JOBS; i++) {
    //for(j=1; j<=NO_JOBS; j++) if (delay[i][j]>0) cout <<"  DPC["<<i<<","<<j<<"] = "<< delay[i][j]<<endl;
  }

  /* 2. Update of bounds based on delayed precedence constraints (PDCs) */
  FLAG = 1;
  ROUNDS = 5;
  k=0;
  while ((FLAG>0) && (k<=ROUNDS)) {
    FLAG = 0;
    k += 1;
    for(i=1; i<=NO_JOBS; i++) {
      for(j=1; j<=NO_JOBS; j++) {
	if(delay[i][j]>0) {
	  if(release[j]<release[i]+delay[i][j]) {
	    release[j]=release[i]+delay[i][j];
	    FLAG=1;
          CHNG=1;
	  }
	  if(due[i]>due[j]-delay[i][j]) {
	    due[i]=due[j]-delay[i][j];
	    FLAG=1;
          CHNG=1;
	  }
	}  
      }
    }
  }
  //cout << "DPC Tightening " << endl;
  //for(i=1; i<=NO_JOBS; i++) cout <<"  "<<i <<">  r="<<release[i]<<"  d="<<due[i]<< "  p="<<proc_time[i]<<endl;
  
  /* 3. Edge-Finding Algorithm -------------------------------------------- */
  /* 3.1. Sort operations by ascending release times: Use index array ----- */

  for(i=1; i<=NO_JOBS; i++) {
    for(j=NO_JOBS; j>=i; j--) {
      if (release[sindex[j-1]] > release[sindex[j]]) {
	t=sindex[j-1];  sindex[j-1]=sindex[j];   sindex[j]=t;
      }
    }
  }

  //cout << "Sorted Data by Ascending Release Times" << endl;
  //for(i=1; i<=NO_JOBS; i++) cout <<"  "<<i <<">  r="<<release[sindex[i]]<<"  d="<<due[sindex[i]]<< "  p="<<proc_time[sindex[i]]<<endl;

  /* 3.2. Tightening of Release Times -------------------------------------- */

  for(i=1; i<=NO_JOBS; i++) release2[sindex[i]]=release[sindex[i]];
  for(k=1; k<=NO_JOBS; k++) {
    P=0;   C=-10000;     H=-10000;
    for(i=NO_JOBS; i>=1; i--) {
      if (due[sindex[i]]<=due[sindex[k]]) {
	P += proc_time[sindex[i]];
	if (C<release[sindex[i]]+P) {
	  C = release[sindex[i]]+P;
	}
	if (C>due[sindex[k]]) {
	  //cout << "There is no feasible schedule" << endl;
	  INF=1;
	}
      }
      CI[sindex[i]]=C;
    }
    for(i=1; i<=NO_JOBS; i++) {
      if (due[sindex[i]]<=due[sindex[k]]) {
	if (H<release[sindex[i]]+P) {
	  H=release[sindex[i]]+P;
	}
	P -= proc_time[sindex[i]];
      }
      else {
	if ((release[sindex[i]]+P+proc_time[sindex[i]]>due[sindex[k]]) && (CI[sindex[i]]>release2[sindex[i]])) {
	  release2[sindex[i]]=CI[sindex[i]];
        CHNG=1;
	}
	if ((H+proc_time[sindex[i]]>due[sindex[k]]) && (C>release2[sindex[i]])) {
	  release2[sindex[i]]=C;
        CHNG=1;
	}
      }
    }
  }
  for(i=1; i<=NO_JOBS; i++)  release[sindex[i]] = release2[sindex[i]];

  //cout <<"Edge-Finding: Tightening of Release Times " << endl; 
  //for(i=1; i<=NO_JOBS; i++) cout <<"  "<<i <<">  r="<<release[sindex[i]]<<"  d="<<due[sindex[i]]<< "  p="<<proc_time[sindex[i]]<<endl;

  /* 3.3. Sort operations by descending due times: Use index array ---------------- */ 
  for(i=0; i<=NO_JOBS; i++)     sindex[i]=i;

  for(i=1; i<=NO_JOBS; i++) {
    for(j=NO_JOBS; j>=i; j--) {
      if (due[sindex[j-1]] < due[sindex[j]]) {
	t=sindex[j-1];  sindex[j-1]=sindex[j];   sindex[j]=t;
      }
    }
  }

  //cout << "Sorted Data by Descending Due Times" << endl;
  //for(i=1; i<=NO_JOBS; i++) cout <<"  "<<i <<">  r="<<release[sindex[i]]<<"  d="<<due[sindex[i]]<< "  p="<<proc_time[sindex[i]]<<endl;

  /* 3.4. Edge-Finding: Tightening of Due Times ----------------------------------- */
  for(i=1; i<=NO_JOBS; i++) due2[sindex[i]]=due[sindex[i]];
  for(i=0; i<=NO_JOBS; i++) CI[i]=0;

  for(k=1; k<=NO_JOBS; k++) {
    P=0;   C=100000;     H=100000;
    for(i=NO_JOBS; i>=1; i--) {
      if (release[sindex[i]]>=release[sindex[k]]) {
	P += proc_time[sindex[i]];
	if (C>due[sindex[i]]-P) {
	  C = due[sindex[i]]-P;
	}
	if (C<release[sindex[k]]) {
	  //cout << "There is no feasible schedule" << endl;
	  INF=1;
	}
      }
      CI[sindex[i]]=C;
    }

    for(i=1; i<=NO_JOBS; i++) {
      if (release[sindex[i]]>=release[sindex[k]]) {
	if (H>due[sindex[i]]-P) {
	  H=due[sindex[i]]-P;
	}
	P -= proc_time[sindex[i]];
      }
      else {

	if ((due[sindex[i]]-P-proc_time[sindex[i]]<release[sindex[k]]) && (due[sindex[i]]>CI[sindex[i]])) {
	  due2[sindex[i]]=CI[sindex[i]];
        CHNG=1;
	}
	if ((H-proc_time[sindex[i]]<release[sindex[k]]) && (due[sindex[i]]>C)) {
	  due2[sindex[i]]=C;
        CHNG=1;
	}
      }
    }
  }
  for(i=1; i<=NO_JOBS; i++)  due[sindex[i]] = due2[sindex[i]];

  //cout <<"Edge-Finding: Tightening of Due Times " << endl; 
  //for(i=1; i<=NO_JOBS; i++) cout <<"  "<<i <<">  r="<<release[sindex[i]]<<"  d="<<due[sindex[i]]<< "  p="<<proc_time[sindex[i]]<<endl;

  /* 4.1. Convert due times back to end of time windows ---------------------------- */
  for (i=1; i<=NO_JOBS; i++) due -= proc_time[i];

  /* 4.2. Calculation of return value ---------------------------------------------- */
  if (INF==1) {
    return -1;
  }
  else if (CHNG==1) {
    return 1;
  }
  else {
    return 0;
  }

}