/*
   - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
   SLEPc - Scalable Library for Eigenvalue Problem Computations
   Copyright (c) 2002-2021, Universitat Politecnica de Valencia, Spain

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

static char help[] = "Tests multiple calls to NEPSolve(). Based on ex22.c.\n\n"
  "The command line options are:\n"
  "  -n <n>, where <n> = number of grid subdivisions.\n"
  "  -tau <tau>, where <tau> is the delay parameter.\n\n";

/*
   Solve parabolic partial differential equation with time delay tau

            u_t = u_xx + a*u(t) + b*u(t-tau)
            u(0,t) = u(pi,t) = 0

   with a = 20 and b(x) = -4.1+x*(1-exp(x-pi)).

   Discretization leads to a DDE of dimension n

            -u' = A*u(t) + B*u(t-tau)

   which results in the nonlinear eigenproblem

            (-lambda*I + A + exp(-tau*lambda)*B)*u = 0
*/

#include <slepcnep.h>

/*
   Check if computed eigenvectors have unit norm
*/
PetscErrorCode CheckNormalizedVectors(NEP nep)
{
  PetscErrorCode ierr;
  PetscInt       i,nconv;
  Mat            A;
  Vec            xr,xi;
  PetscReal      error=0.0,normr;
#if !defined(PETSC_USE_COMPLEX)
  PetscReal      normi;
#endif

  PetscFunctionBeginUser;
  ierr = NEPGetConverged(nep,&nconv);CHKERRQ(ierr);
  if (nconv>0) {
    ierr = NEPGetSplitOperatorTerm(nep,0,&A,NULL);CHKERRQ(ierr);
    ierr = MatCreateVecs(A,&xr,&xi);CHKERRQ(ierr);
    for (i=0;i<nconv;i++) {
      ierr = NEPGetEigenpair(nep,i,NULL,NULL,xr,xi);CHKERRQ(ierr);
#if defined(PETSC_USE_COMPLEX)
      ierr = VecNorm(xr,NORM_2,&normr);CHKERRQ(ierr);
      error = PetscMax(error,PetscAbsReal(normr-PetscRealConstant(1.0)));
#else
      ierr = VecNormBegin(xr,NORM_2,&normr);CHKERRQ(ierr);
      ierr = VecNormBegin(xi,NORM_2,&normi);CHKERRQ(ierr);
      ierr = VecNormEnd(xr,NORM_2,&normr);CHKERRQ(ierr);
      ierr = VecNormEnd(xi,NORM_2,&normi);CHKERRQ(ierr);
      error = PetscMax(error,PetscAbsReal(SlepcAbsEigenvalue(normr,normi)-PetscRealConstant(1.0)));
#endif
    }
    ierr = VecDestroy(&xr);CHKERRQ(ierr);
    ierr = VecDestroy(&xi);CHKERRQ(ierr);
    if (error>100*PETSC_MACHINE_EPSILON) {
      ierr = PetscPrintf(PETSC_COMM_WORLD,"Vectors are not normalized. Error=%g\n",(double)error);CHKERRQ(ierr);
    }
  }
  PetscFunctionReturn(0);
}

int main(int argc,char **argv)
{
  NEP            nep;             /* nonlinear eigensolver context */
  Mat            Id,A,B;          /* problem matrices */
  FN             f1,f2,f3;        /* functions to define the nonlinear operator */
  Mat            mats[3];
  FN             funs[3];
  PetscScalar    coeffs[2],b;
  PetscInt       n=128,Istart,Iend,i;
  PetscReal      tau=0.001,h,a=20,xi;
  PetscBool      skipnorm=PETSC_FALSE;
  PetscErrorCode ierr;

  ierr = SlepcInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;
  ierr = PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);CHKERRQ(ierr);
  ierr = PetscOptionsGetReal(NULL,NULL,"-tau",&tau,NULL);CHKERRQ(ierr);
  ierr = PetscOptionsGetBool(NULL,NULL,"-skipnorm",&skipnorm,NULL);CHKERRQ(ierr);
  ierr = PetscPrintf(PETSC_COMM_WORLD,"\n1-D Delay Eigenproblem, n=%D, tau=%g\n\n",n,(double)tau);CHKERRQ(ierr);
  h = PETSC_PI/(PetscReal)(n+1);

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
             Create functions that define the split operator
     - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

  /* f1=-lambda */
  ierr = FNCreate(PETSC_COMM_WORLD,&f1);CHKERRQ(ierr);
  ierr = FNSetType(f1,FNRATIONAL);CHKERRQ(ierr);
  coeffs[0] = -1.0; coeffs[1] = 0.0;
  ierr = FNRationalSetNumerator(f1,2,coeffs);CHKERRQ(ierr);

  /* f2=1.0 */
  ierr = FNCreate(PETSC_COMM_WORLD,&f2);CHKERRQ(ierr);
  ierr = FNSetType(f2,FNRATIONAL);CHKERRQ(ierr);
  coeffs[0] = 1.0;
  ierr = FNRationalSetNumerator(f2,1,coeffs);CHKERRQ(ierr);

  /* f3=exp(-tau*lambda) */
  ierr = FNCreate(PETSC_COMM_WORLD,&f3);CHKERRQ(ierr);
  ierr = FNSetType(f3,FNEXP);CHKERRQ(ierr);
  ierr = FNSetScale(f3,-tau,1.0);CHKERRQ(ierr);

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
                         Create problem matrices
     - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

  /* Identity matrix */
  ierr = MatCreate(PETSC_COMM_WORLD,&Id);CHKERRQ(ierr);
  ierr = MatSetSizes(Id,PETSC_DECIDE,PETSC_DECIDE,n,n);CHKERRQ(ierr);
  ierr = MatSetFromOptions(Id);CHKERRQ(ierr);
  ierr = MatSetUp(Id);CHKERRQ(ierr);
  ierr = MatGetOwnershipRange(Id,&Istart,&Iend);CHKERRQ(ierr);
  for (i=Istart;i<Iend;i++) {
    ierr = MatSetValue(Id,i,i,1.0,INSERT_VALUES);CHKERRQ(ierr);
  }
  ierr = MatAssemblyBegin(Id,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
  ierr = MatAssemblyEnd(Id,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
  ierr = MatSetOption(Id,MAT_HERMITIAN,PETSC_TRUE);CHKERRQ(ierr);

  /* A = 1/h^2*tridiag(1,-2,1) + a*I */
  ierr = MatCreate(PETSC_COMM_WORLD,&A);CHKERRQ(ierr);
  ierr = MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,n,n);CHKERRQ(ierr);
  ierr = MatSetFromOptions(A);CHKERRQ(ierr);
  ierr = MatSetUp(A);CHKERRQ(ierr);
  ierr = MatGetOwnershipRange(A,&Istart,&Iend);CHKERRQ(ierr);
  for (i=Istart;i<Iend;i++) {
    if (i>0) { ierr = MatSetValue(A,i,i-1,1.0/(h*h),INSERT_VALUES);CHKERRQ(ierr); }
    if (i<n-1) { ierr = MatSetValue(A,i,i+1,1.0/(h*h),INSERT_VALUES);CHKERRQ(ierr); }
    ierr = MatSetValue(A,i,i,-2.0/(h*h)+a,INSERT_VALUES);CHKERRQ(ierr);
  }
  ierr = MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
  ierr = MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
  ierr = MatSetOption(A,MAT_HERMITIAN,PETSC_TRUE);CHKERRQ(ierr);

  /* B = diag(b(xi)) */
  ierr = MatCreate(PETSC_COMM_WORLD,&B);CHKERRQ(ierr);
  ierr = MatSetSizes(B,PETSC_DECIDE,PETSC_DECIDE,n,n);CHKERRQ(ierr);
  ierr = MatSetFromOptions(B);CHKERRQ(ierr);
  ierr = MatSetUp(B);CHKERRQ(ierr);
  ierr = MatGetOwnershipRange(B,&Istart,&Iend);CHKERRQ(ierr);
  for (i=Istart;i<Iend;i++) {
    xi = (i+1)*h;
    b = -4.1+xi*(1.0-PetscExpReal(xi-PETSC_PI));
    ierr = MatSetValue(B,i,i,b,INSERT_VALUES);CHKERRQ(ierr);
  }
  ierr = MatAssemblyBegin(B,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
  ierr = MatAssemblyEnd(B,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
  ierr = MatSetOption(B,MAT_HERMITIAN,PETSC_TRUE);CHKERRQ(ierr);

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
              Create nonlinear eigensolver and set options
     - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

  ierr = NEPCreate(PETSC_COMM_WORLD,&nep);CHKERRQ(ierr);
  mats[0] = A;  funs[0] = f2;
  mats[1] = Id; funs[1] = f1;
  mats[2] = B;  funs[2] = f3;
  ierr = NEPSetSplitOperator(nep,3,mats,funs,SUBSET_NONZERO_PATTERN);CHKERRQ(ierr);
  ierr = NEPSetTolerances(nep,1e-9,PETSC_DEFAULT);CHKERRQ(ierr);
  ierr = NEPSetFromOptions(nep);CHKERRQ(ierr);

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
                      Solve the eigensystem
     - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

  ierr = NEPSolve(nep);CHKERRQ(ierr);
  ierr = NEPErrorView(nep,NEP_ERROR_RELATIVE,NULL);CHKERRQ(ierr);
  if (!skipnorm) { ierr = CheckNormalizedVectors(nep);CHKERRQ(ierr); }

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
                   Create problem matrices of size 2*n
     - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

  ierr = MatDestroy(&Id);CHKERRQ(ierr);
  ierr = MatDestroy(&A);CHKERRQ(ierr);
  ierr = MatDestroy(&B);CHKERRQ(ierr);
  n *= 2;
  ierr = PetscPrintf(PETSC_COMM_WORLD,"\n1-D Delay Eigenproblem, n=%D, tau=%g\n\n",n,(double)tau);CHKERRQ(ierr);
  h = PETSC_PI/(PetscReal)(n+1);

  /* Identity matrix */
  ierr = MatCreate(PETSC_COMM_WORLD,&Id);CHKERRQ(ierr);
  ierr = MatSetSizes(Id,PETSC_DECIDE,PETSC_DECIDE,n,n);CHKERRQ(ierr);
  ierr = MatSetFromOptions(Id);CHKERRQ(ierr);
  ierr = MatSetUp(Id);CHKERRQ(ierr);
  ierr = MatGetOwnershipRange(Id,&Istart,&Iend);CHKERRQ(ierr);
  for (i=Istart;i<Iend;i++) {
    ierr = MatSetValue(Id,i,i,1.0,INSERT_VALUES);CHKERRQ(ierr);
  }
  ierr = MatAssemblyBegin(Id,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
  ierr = MatAssemblyEnd(Id,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
  ierr = MatSetOption(Id,MAT_HERMITIAN,PETSC_TRUE);CHKERRQ(ierr);

  /* A = 1/h^2*tridiag(1,-2,1) + a*I */
  ierr = MatCreate(PETSC_COMM_WORLD,&A);CHKERRQ(ierr);
  ierr = MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,n,n);CHKERRQ(ierr);
  ierr = MatSetFromOptions(A);CHKERRQ(ierr);
  ierr = MatSetUp(A);CHKERRQ(ierr);
  ierr = MatGetOwnershipRange(A,&Istart,&Iend);CHKERRQ(ierr);
  for (i=Istart;i<Iend;i++) {
    if (i>0) { ierr = MatSetValue(A,i,i-1,1.0/(h*h),INSERT_VALUES);CHKERRQ(ierr); }
    if (i<n-1) { ierr = MatSetValue(A,i,i+1,1.0/(h*h),INSERT_VALUES);CHKERRQ(ierr); }
    ierr = MatSetValue(A,i,i,-2.0/(h*h)+a,INSERT_VALUES);CHKERRQ(ierr);
  }
  ierr = MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
  ierr = MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
  ierr = MatSetOption(A,MAT_HERMITIAN,PETSC_TRUE);CHKERRQ(ierr);

  /* B = diag(b(xi)) */
  ierr = MatCreate(PETSC_COMM_WORLD,&B);CHKERRQ(ierr);
  ierr = MatSetSizes(B,PETSC_DECIDE,PETSC_DECIDE,n,n);CHKERRQ(ierr);
  ierr = MatSetFromOptions(B);CHKERRQ(ierr);
  ierr = MatSetUp(B);CHKERRQ(ierr);
  ierr = MatGetOwnershipRange(B,&Istart,&Iend);CHKERRQ(ierr);
  for (i=Istart;i<Iend;i++) {
    xi = (i+1)*h;
    b = -4.1+xi*(1.0-PetscExpReal(xi-PETSC_PI));
    ierr = MatSetValue(B,i,i,b,INSERT_VALUES);CHKERRQ(ierr);
  }
  ierr = MatAssemblyBegin(B,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
  ierr = MatAssemblyEnd(B,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
  ierr = MatSetOption(B,MAT_HERMITIAN,PETSC_TRUE);CHKERRQ(ierr);

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
       Solve again, calling NEPReset() since matrix size has changed
     - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

  /*ierr = NEPReset(nep);CHKERRQ(ierr);*/  /* not required, will be called in NEPSetSplitOperators() */
  mats[0] = A;  funs[0] = f2;
  mats[1] = Id; funs[1] = f1;
  mats[2] = B;  funs[2] = f3;
  ierr = NEPSetSplitOperator(nep,3,mats,funs,SUBSET_NONZERO_PATTERN);CHKERRQ(ierr);
  ierr = NEPSolve(nep);CHKERRQ(ierr);
  ierr = NEPErrorView(nep,NEP_ERROR_RELATIVE,NULL);CHKERRQ(ierr);
  if (!skipnorm) { ierr = CheckNormalizedVectors(nep);CHKERRQ(ierr); }

  ierr = NEPDestroy(&nep);CHKERRQ(ierr);
  ierr = MatDestroy(&Id);CHKERRQ(ierr);
  ierr = MatDestroy(&A);CHKERRQ(ierr);
  ierr = MatDestroy(&B);CHKERRQ(ierr);
  ierr = FNDestroy(&f1);CHKERRQ(ierr);
  ierr = FNDestroy(&f2);CHKERRQ(ierr);
  ierr = FNDestroy(&f3);CHKERRQ(ierr);
  ierr = SlepcFinalize();
  return ierr;
}

/*TEST

   testset:
      nsize: 2
      requires: !single
      output_file: output/test10_1.out
      test:
         suffix: 1
         args: -nep_type narnoldi -nep_target 0.55
      test:
         suffix: 1_rii
         args: -nep_type rii -nep_target 0.55 -nep_rii_hermitian
      test:
         suffix: 1_narnoldi
         args: -nep_type narnoldi -nep_target 0.55 -nep_narnoldi_lag_preconditioner 2
      test:
         suffix: 1_slp
         args: -nep_type slp -nep_slp_st_pc_type redundant
      test:
         suffix: 1_interpol
         args: -nep_type interpol -rg_type interval -rg_interval_endpoints .5,1,-.1,.1 -nep_target .7 -nep_interpol_st_pc_type redundant
      test:
         suffix: 1_narnoldi_sync
         args: -nep_type narnoldi -ds_parallel synchronized

   testset:
      args: -nep_nev 2 -rg_type interval -rg_interval_endpoints .5,15,-.1,.1 -nep_target .7
      requires: !single
      output_file: output/test10_2.out
      test:
         suffix: 2_interpol
         args: -nep_type interpol -nep_interpol_pep_type jd -nep_interpol_st_pc_type sor
      test:
         suffix: 2_nleigs
         args: -nep_type nleigs
         requires: complex
      test:
         suffix: 2_nleigs_real
         args: -nep_type nleigs -rg_interval_endpoints .5,15
         requires: !complex

TEST*/
