/*
   - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
   SLEPc - Scalable Library for Eigenvalue Problem Computations
   Copyright (c) 2002-, Universitat Politecnica de Valencia, Spain

   This file is part of SLEPc.
   SLEPc is distributed under a 2-clause BSD license (see LICENSE).
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*/

static char help[] = "Generalized Symmetric eigenproblem.\n\n"
  "The problem is Ax = lambda Bx, with:\n"
  "   A = Laplacian operator in 2-D\n"
  "   B = diagonal matrix with all values equal to 4 except nulldim zeros\n\n"
  "The command line options are:\n"
  "  -n <n>, where <n> = number of grid subdivisions in x dimension.\n"
  "  -m <m>, where <m> = number of grid subdivisions in y dimension.\n"
  "  -nulldim <k>, where <k> = dimension of the nullspace of B.\n\n";

#include <slepceps.h>

int main(int argc,char **argv)
{
  Mat            A,B;         /* matrices */
  EPS            eps;         /* eigenproblem solver context */
  EPSType        type;
  PetscInt       N,n=10,m,Istart,Iend,II,nev,i,j,nulldim=0;
  PetscBool      flag,terse;

  PetscFunctionBeginUser;
  PetscCall(SlepcInitialize(&argc,&argv,(char*)0,help));

  PetscCall(PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL));
  PetscCall(PetscOptionsGetInt(NULL,NULL,"-m",&m,&flag));
  if (!flag) m=n;
  N = n*m;
  PetscCall(PetscOptionsGetInt(NULL,NULL,"-nulldim",&nulldim,NULL));
  PetscCall(PetscPrintf(PETSC_COMM_WORLD,"\nGeneralized Symmetric Eigenproblem, N=%" PetscInt_FMT " (%" PetscInt_FMT "x%" PetscInt_FMT " grid), null(B)=%" PetscInt_FMT "\n\n",N,n,m,nulldim));

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     Compute the matrices that define the eigensystem, Ax=kBx
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  PetscCall(MatCreate(PETSC_COMM_WORLD,&A));
  PetscCall(MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,N,N));
  PetscCall(MatSetFromOptions(A));

  PetscCall(MatCreate(PETSC_COMM_WORLD,&B));
  PetscCall(MatSetSizes(B,PETSC_DECIDE,PETSC_DECIDE,N,N));
  PetscCall(MatSetFromOptions(B));

  PetscCall(MatGetOwnershipRange(A,&Istart,&Iend));
  for (II=Istart;II<Iend;II++) {
    i = II/n; j = II-i*n;
    if (i>0) PetscCall(MatSetValue(A,II,II-n,-1.0,INSERT_VALUES));
    if (i<m-1) PetscCall(MatSetValue(A,II,II+n,-1.0,INSERT_VALUES));
    if (j>0) PetscCall(MatSetValue(A,II,II-1,-1.0,INSERT_VALUES));
    if (j<n-1) PetscCall(MatSetValue(A,II,II+1,-1.0,INSERT_VALUES));
    PetscCall(MatSetValue(A,II,II,4.0,INSERT_VALUES));
    if (II>=nulldim) PetscCall(MatSetValue(B,II,II,4.0,INSERT_VALUES));
  }

  PetscCall(MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY));
  PetscCall(MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY));
  PetscCall(MatAssemblyBegin(B,MAT_FINAL_ASSEMBLY));
  PetscCall(MatAssemblyEnd(B,MAT_FINAL_ASSEMBLY));

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
                Create the eigensolver and set various options
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  /*
     Create eigensolver context
  */
  PetscCall(EPSCreate(PETSC_COMM_WORLD,&eps));

  /*
     Set operators. In this case, it is a generalized eigenvalue problem
  */
  PetscCall(EPSSetOperators(eps,A,B));
  PetscCall(EPSSetProblemType(eps,EPS_GHEP));

  /*
     Set solver parameters at runtime
  */
  PetscCall(EPSSetFromOptions(eps));

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
                      Solve the eigensystem
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  PetscCall(EPSSolve(eps));

  /*
     Optional: Get some information from the solver and display it
  */
  PetscCall(EPSGetType(eps,&type));
  PetscCall(PetscPrintf(PETSC_COMM_WORLD," Solution method: %s\n\n",type));
  PetscCall(EPSGetDimensions(eps,&nev,NULL,NULL));
  PetscCall(PetscPrintf(PETSC_COMM_WORLD," Number of requested eigenvalues: %" PetscInt_FMT "\n",nev));

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
                    Display solution and clean up
     - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

  /* show detailed info unless -terse option is given by user */
  PetscCall(PetscOptionsHasName(NULL,NULL,"-terse",&terse));
  if (terse) PetscCall(EPSErrorView(eps,EPS_ERROR_RELATIVE,NULL));
  else {
    PetscCall(PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_INFO_DETAIL));
    PetscCall(EPSConvergedReasonView(eps,PETSC_VIEWER_STDOUT_WORLD));
    PetscCall(EPSErrorView(eps,EPS_ERROR_RELATIVE,PETSC_VIEWER_STDOUT_WORLD));
    PetscCall(PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD));
  }
  PetscCall(EPSDestroy(&eps));
  PetscCall(MatDestroy(&A));
  PetscCall(MatDestroy(&B));
  PetscCall(SlepcFinalize());
  return 0;
}

/*TEST

   test:
      suffix: 1
      args: -eps_nev 4 -eps_ncv 22 -eps_tol 1e-5 -st_type sinvert -terse
      filter: grep -v Solution

   test:
      suffix: 2
      args: -n 110 -nulldim 6 -eps_nev 4 -eps_ncv 18 -eps_tol 1e-5 -eps_purify 1 -st_type sinvert -st_matstructure {{different subset}} -terse
      requires: !single

   test:
      suffix: 3
      args: -eps_nev 3 -eps_tol 1e-5 -mat_type sbaij -st_type sinvert -terse

   test:
      suffix: 4
      args: -eps_nev 4 -eps_tol 1e-4 -eps_smallest_real -eps_type {{gd lobpcg rqcg}} -terse
      output_file: output/ex13_1.out
      filter: grep -v Solution

   test:
      suffix: 5_primme
      args: -n 10 -m 12 -eps_nev 4 -eps_target 0.9 -eps_max_it 15000 -eps_type primme -st_pc_type jacobi -terse
      requires: primme defined(SLEPC_HAVE_PRIMME3) !single

   test:
      suffix: 6
      nsize: 2
      args: -eps_type ciss -rg_type ellipse -rg_ellipse_center 1.4 -rg_ellipse_radius 0.1 -eps_ciss_partitions 2 -terse
      requires: !single

TEST*/
