/*
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   SLEPc - Scalable Library for Eigenvalue Problem Computations
   Copyright (c) 2002-2019, 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[] = "Solve a quadratic problem with PEPLINEAR with a user-provided EPS.\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\n";

#include <slepcpep.h>

int main(int argc,char **argv)
{
  Mat            M,C,K,A[3];
  PEP            pep;
  PetscInt       N,n=10,m,Istart,Iend,II,i,j;
  PetscBool      flag,expmat;
  PetscReal      alpha,beta;
  EPS            eps;
  ST             st;
  KSP            ksp;
  PC             pc;
  PetscErrorCode ierr;

  ierr = SlepcInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;
  ierr = PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);CHKERRQ(ierr);
  ierr = PetscOptionsGetInt(NULL,NULL,"-m",&m,&flag);CHKERRQ(ierr);
  if (!flag) m=n;
  N = n*m;
  ierr = PetscPrintf(PETSC_COMM_WORLD,"\nQuadratic Eigenproblem, N=%D (%Dx%D grid)\n\n",N,n,m);CHKERRQ(ierr);

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     Compute the matrices that define the eigensystem, (k^2*M+k*C+K)x=0
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  /* K is the 2-D Laplacian */
  ierr = MatCreate(PETSC_COMM_WORLD,&K);CHKERRQ(ierr);
  ierr = MatSetSizes(K,PETSC_DECIDE,PETSC_DECIDE,N,N);CHKERRQ(ierr);
  ierr = MatSetFromOptions(K);CHKERRQ(ierr);
  ierr = MatSetUp(K);CHKERRQ(ierr);
  ierr = MatGetOwnershipRange(K,&Istart,&Iend);CHKERRQ(ierr);
  for (II=Istart;II<Iend;II++) {
    i = II/n; j = II-i*n;
    if (i>0) { ierr = MatSetValue(K,II,II-n,-1.0,INSERT_VALUES);CHKERRQ(ierr); }
    if (i<m-1) { ierr = MatSetValue(K,II,II+n,-1.0,INSERT_VALUES);CHKERRQ(ierr); }
    if (j>0) { ierr = MatSetValue(K,II,II-1,-1.0,INSERT_VALUES);CHKERRQ(ierr); }
    if (j<n-1) { ierr = MatSetValue(K,II,II+1,-1.0,INSERT_VALUES);CHKERRQ(ierr); }
    ierr = MatSetValue(K,II,II,4.0,INSERT_VALUES);CHKERRQ(ierr);
  }
  ierr = MatAssemblyBegin(K,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
  ierr = MatAssemblyEnd(K,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);

  /* C is the 1-D Laplacian on horizontal lines */
  ierr = MatCreate(PETSC_COMM_WORLD,&C);CHKERRQ(ierr);
  ierr = MatSetSizes(C,PETSC_DECIDE,PETSC_DECIDE,N,N);CHKERRQ(ierr);
  ierr = MatSetFromOptions(C);CHKERRQ(ierr);
  ierr = MatSetUp(C);CHKERRQ(ierr);
  ierr = MatGetOwnershipRange(C,&Istart,&Iend);CHKERRQ(ierr);
  for (II=Istart;II<Iend;II++) {
    i = II/n; j = II-i*n;
    if (j>0) { ierr = MatSetValue(C,II,II-1,-1.0,INSERT_VALUES);CHKERRQ(ierr); }
    if (j<n-1) { ierr = MatSetValue(C,II,II+1,-1.0,INSERT_VALUES);CHKERRQ(ierr); }
    ierr = MatSetValue(C,II,II,2.0,INSERT_VALUES);CHKERRQ(ierr);
  }
  ierr = MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
  ierr = MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);

  /* M is a diagonal matrix */
  ierr = MatCreate(PETSC_COMM_WORLD,&M);CHKERRQ(ierr);
  ierr = MatSetSizes(M,PETSC_DECIDE,PETSC_DECIDE,N,N);CHKERRQ(ierr);
  ierr = MatSetFromOptions(M);CHKERRQ(ierr);
  ierr = MatSetUp(M);CHKERRQ(ierr);
  ierr = MatGetOwnershipRange(M,&Istart,&Iend);CHKERRQ(ierr);
  for (II=Istart;II<Iend;II++) {
    ierr = MatSetValue(M,II,II,(PetscReal)(II+1),INSERT_VALUES);CHKERRQ(ierr);
  }
  ierr = MatAssemblyBegin(M,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
  ierr = MatAssemblyEnd(M,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
             Create a standalone EPS with appropriate settings
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  ierr = EPSCreate(PETSC_COMM_WORLD,&eps);CHKERRQ(ierr);
  ierr = EPSSetWhichEigenpairs(eps,EPS_TARGET_MAGNITUDE);CHKERRQ(ierr);
#if defined(PETSC_USE_COMPLEX)
  ierr = EPSSetTarget(eps,0.01*PETSC_i);CHKERRQ(ierr);
#endif
  ierr = EPSGetST(eps,&st);CHKERRQ(ierr);
  ierr = STSetType(st,STSINVERT);CHKERRQ(ierr);
  ierr = STGetKSP(st,&ksp);CHKERRQ(ierr);
  ierr = KSPSetType(ksp,KSPBCGS);CHKERRQ(ierr);
  ierr = KSPGetPC(ksp,&pc);CHKERRQ(ierr);
  ierr = PCSetType(pc,PCJACOBI);CHKERRQ(ierr);
  ierr = EPSSetFromOptions(eps);CHKERRQ(ierr);

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
             Create the eigensolver and solve the eigensystem
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  ierr = PEPCreate(PETSC_COMM_WORLD,&pep);CHKERRQ(ierr);
  ierr = PetscObjectSetName((PetscObject)pep,"PEP_solver");CHKERRQ(ierr);
  A[0] = K; A[1] = C; A[2] = M;
  ierr = PEPSetOperators(pep,3,A);CHKERRQ(ierr);
  ierr = PEPSetType(pep,PEPLINEAR);CHKERRQ(ierr);
  ierr = PEPSetProblemType(pep,PEP_GENERAL);CHKERRQ(ierr);
  ierr = PEPLinearSetEPS(pep,eps);CHKERRQ(ierr);
  ierr = PEPSetFromOptions(pep);CHKERRQ(ierr);
  ierr = PEPSolve(pep);CHKERRQ(ierr);
  ierr = PEPLinearGetLinearization(pep,&alpha,&beta);CHKERRQ(ierr);
  ierr = PetscPrintf(PETSC_COMM_WORLD," Linearization with alpha=%g, beta=%g",(double)alpha,(double)beta);CHKERRQ(ierr);
  ierr = PEPLinearGetExplicitMatrix(pep,&expmat);CHKERRQ(ierr);
  if (expmat) {
    ierr = PetscPrintf(PETSC_COMM_WORLD," with explicit matrix");CHKERRQ(ierr);
  }
  ierr = PetscPrintf(PETSC_COMM_WORLD,"\n");CHKERRQ(ierr);

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

  ierr = PEPErrorView(pep,PEP_ERROR_BACKWARD,NULL);CHKERRQ(ierr);
  ierr = PEPDestroy(&pep);CHKERRQ(ierr);
  ierr = EPSDestroy(&eps);CHKERRQ(ierr);
  ierr = MatDestroy(&M);CHKERRQ(ierr);
  ierr = MatDestroy(&C);CHKERRQ(ierr);
  ierr = MatDestroy(&K);CHKERRQ(ierr);
  ierr = SlepcFinalize();
  return ierr;
}

/*TEST

   test:
      suffix: 1
      args: -pep_linear_explicitmatrix -pep_view_vectors ::ascii_info

TEST*/
