/*
 * Copyright (c) 2005-2017 National Technology & Engineering Solutions
 * of Sandia, LLC (NTESS).  Under the terms of Contract DE-NA0003525 with
 * NTESS, the U.S. Government retains certain rights in this software.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *
 *     * 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.
 *
 *     * Neither the name of NTESS nor the names of its
 *       contributors may 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.
 *
 */

#include "structs.h"
#include <stdio.h> // for fprintf, printf, NULL, FILE

/* Check an extended eigenpair of A by direct multiplication. Uses
   the Ay = extval*y + Dg form of the problem for convenience. */

double checkeig_ext(double *err, double *work, /* work vector of length n */
                    struct vtx_data **A, double *y, int n, double extval, double *vwsqrt,
                    double *gvec, double eigtol,
                    int warnings /* don't want to see warning messages in one of the
                                    contexts this is called */
)
{
  extern FILE *Output_File;   /* output file or null */
  extern int   DEBUG_EVECS;   /* print debugging output? */
  extern int   WARNING_EVECS; /* print warning messages? */
  double       resid;         /* the extended eigen residual */
  double       ch_norm();     /* vector norm */
  void         splarax();     /* sparse matrix vector mult */
  void         scadd();       /* scaled vector add */
  void         scale_diag();  /* scale vector by another's elements */
  void         cpvec();       /* vector copy */

  splarax(err, A, n, y, vwsqrt, work);
  scadd(err, 1, n, -extval, y);
  cpvec(work, 1, n, gvec); /* only need if going to re-use gvec */
  scale_diag(work, 1, n, vwsqrt);
  scadd(err, 1, n, -1.0, work);
  resid = ch_norm(err, 1, n);

  if (DEBUG_EVECS > 0) {
    printf("  extended residual: %g\n", resid);
    if (Output_File != NULL) {
      fprintf(Output_File, "  extended residual: %g\n", resid);
    }
  }
  if (warnings && WARNING_EVECS > 0 && resid > eigtol) {
    printf("WARNING: Extended residual (%g) greater than tolerance (%g).\n", resid, eigtol);
    if (Output_File != NULL) {
      fprintf(Output_File, "WARNING: Extended residual (%g) greater than tolerance (%g).\n", resid,
              eigtol);
    }
  }

  return (resid);
}
