/* F11JB_P0W_F C++ Header Example Program.
 *
 * Copyright 2020 Numerical Algorithms Group.
 * Mark 27.1, 2020.
 */
#include <dco_light.hpp>
#include <nag.h>
#include <nagx04.h>
#include <nagad.h>
#include <stdio.h>
#include <iostream>
using namespace std;

extern "C"
{
  static void NAG_CALL do_rcm (void *&ad_handle,
                               Integer &n,
                               Integer &nnz,
                               Integer irow[], Integer icol[],
                               double a[], double y[],
                               Integer istr[],
                               Integer perm_fwd[], Integer perm_inv[],
                               Integer iwork[]);
}

int main(void)
{
  int      exit_status = 0;
  void     *ad_handle = 0;
  Integer  ifail = 0;

  cout << "F11JB_P0W_F C++ Header Example Program Results\n\n";
  // Skip heading in data file
  string   mystr;
  getline (cin, mystr);

  // Read order of matrix and number of nonzero entries
  Integer  n, nnz;
  cin >> n;
  cin >> nnz;

  Integer  la = 3*nnz;
  Integer  liwork = 2*la + 7*n + 1;
  double   *a=0, *x=0, *y=0;
  Integer  *icol=0, *ipiv=0, *irow=0, *istr=0, *iwork=0;
  Integer  *perm_fwd=0, *perm_inv=0;

  a        = new double [la];
  x        = new double [n];
  y        = new double [n];
  icol     = new Integer [la];
  ipiv     = new Integer [n];
  irow     = new Integer [la];
  istr     = new Integer [n+1];
  iwork    = new Integer [liwork];
  perm_fwd = new Integer [n];
  perm_inv = new Integer [n];
      
  // Read the matrix A
  for (int i=0; i<nnz; i++) {
    cin >> a[i] >> irow[i] >> icol[i];
  }
      
  // Read the vector y
  for (int i=0; i<n; i++) {
    cin >> y[i];
  }


  ifail = 0;
  // Calculate Cholesky factorization
  Integer  lfill = -1;
  Integer  nnzc, npivm;
  double   dscale, dtol;
  dtol = 0.0;
  dscale = 0.0;

  // Compute reverse Cuthill-McKee permutation for bandwidth reduction
  do_rcm(ad_handle,n,nnz,irow,icol,a,y,istr,perm_fwd,perm_inv,iwork);

  ifail = 0;
  f11ja_p0w_f_(ad_handle,n,nnz,a,la,irow,icol,lfill,dtol,"N",dscale,"M",
               ipiv,istr,nnzc,npivm,iwork,liwork,ifail,1,1);

  // Check the output value of NPIVM
  if (npivm>0) {
    cout << " Factorization is not complete"  << endl;
    goto END;
  }
  
  // Solve P L D L^T P^T x = y
  ifail = 0;
  f11jb_p0w_f_(ad_handle,n,a,la,irow,icol,ipiv,istr,"C",y,x,ifail,1);
    
  // Output results
  cout.setf(ios::scientific,ios::floatfield);
  cout.precision(4);
  cout << "  Solution vector" << endl;
  for (int i=0; i<n; ++i) {
    cout.width(12);cout << x[perm_inv[i]] << endl;
  }

 END:

  delete [] a;
  delete [] x;
  delete [] y;
  delete [] icol;
  delete [] ipiv;
  delete [] irow;
  delete [] istr;
  delete [] iwork;
  delete [] perm_fwd;
  delete [] perm_inv;

  return exit_status;
}

static void NAG_CALL do_rcm(void *&ad_handle,
                            Integer &n,
                            Integer &nnz,
                            Integer irow[], Integer icol[],
                            double a[], double y[],
                            Integer istr[],
                            Integer perm_fwd[], Integer perm_inv[],
                            Integer iwork[]) {
  logical  lopts[5];
  lopts[0] = 0;
  lopts[1] = 0;
  lopts[2] = 1;
  lopts[3] = 1;
  lopts[4] = 1;

  double  *rwork = 0;
  Integer info[4], mask[1];

  // SCS to CS, must add the upper triangle entries.
  Integer j = nnz;
  for (Integer i=0; i<nnz; i++) {
    if (irow[i]>icol[i]) {
      // strictly lower triangle, add the transposed
      a[j] = a[i];
      irow[j] = icol[i];
      icol[j] = irow[i];
      j++;
    }
  }
  
  Integer nnz_cs = j;

  // Reorder, CS to CCS, icolzp in istr
  Integer ifail = 0;
  f11za_p0w_f_(ad_handle,n,nnz_cs,a,icol,irow,"F","F",istr,iwork,ifail,1,1);

  // Calculate reverse Cuthill-McKee
  ifail = 0;
  f11yef_(n,nnz_cs,istr,irow,lopts,mask,perm_fwd,info,ifail);

  // compute inverse perm, in perm_inv
  for (int i = 0; i<n; i++) {
    perm_fwd[i] = perm_fwd[i] - 1;
    perm_inv[perm_fwd[i]] = i;
  }

  // Apply permutation on column/row indices
  Integer *iswapc=0, *iswapr=0;
  iswapc = new Integer [nnz_cs];
  iswapr = new Integer [nnz_cs];
  for (int i=0; i<nnz_cs; i++) {
    iswapc[i] = perm_inv[icol[i]-1];
    iswapr[i] = perm_inv[irow[i]-1];
  }
  for (int i=0; i<nnz_cs; i++) {
    icol[i] = iswapc[i] + 1;
    irow[i] = iswapr[i] + 1;
  }
  delete [] iswapc;
  delete [] iswapr;

  // restrict to lower triangle, SCS format
  // copying entries upwards
  j = 0;
  for (Integer i = 0; i<nnz_cs; i++) {
    if (irow[i]>=icol[i]) {
      // non-upper triangle, bubble up
      a[j] = a[i];
      icol[j] = icol[i];
      irow[j] = irow[i];
      j++;
    }
  }
  
  Integer nnz_scs = j;
  // sort
  ifail = 0;
  f11zb_p0w_f_(ad_handle,n,nnz_scs,a,irow,icol,"S","K",istr,iwork,ifail,1,1);

  // permute rhs vector
  rwork = new double [n];
  for (int i=0; i<n; i++) {
    rwork[i] = y[perm_fwd[i]];
  }
  for (int i=0; i<n; i++) {
    y[i] = rwork[i];
  }
  delete [] rwork;
  return;
}