/*
   - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
   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 EPSSolve changing ncv.\n\n";

#include <slepceps.h>

int main(int argc,char **argv)
{
  Mat            A;
  EPS            eps;
  PetscReal      tol=PetscMax(1000*PETSC_MACHINE_EPSILON,1e-9);
  PetscInt       n=30,i,Istart,Iend,nev,ncv;
  PetscErrorCode ierr;

  ierr = SlepcInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;
  ierr = PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);CHKERRQ(ierr);
  ierr = PetscPrintf(PETSC_COMM_WORLD,"\n1-D Laplacian Eigenproblem, n=%D\n\n",n);CHKERRQ(ierr);

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     Compute the operator matrix that defines the eigensystem, Ax=kx
     - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

  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,INSERT_VALUES);CHKERRQ(ierr); }
    if (i<n-1) { ierr = MatSetValue(A,i,i+1,-1.0,INSERT_VALUES);CHKERRQ(ierr); }
    ierr = MatSetValue(A,i,i,2.0,INSERT_VALUES);CHKERRQ(ierr);
  }
  ierr = MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
  ierr = MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
             Create the solver, call EPSSolve() twice
     - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
  ierr = EPSCreate(PETSC_COMM_WORLD,&eps);CHKERRQ(ierr);
  ierr = EPSSetOperators(eps,A,NULL);CHKERRQ(ierr);
  ierr = EPSSetProblemType(eps,EPS_HEP);CHKERRQ(ierr);
  ierr = EPSSetTolerances(eps,tol,PETSC_DEFAULT);CHKERRQ(ierr);
  ierr = EPSSetWhichEigenpairs(eps,EPS_SMALLEST_REAL);CHKERRQ(ierr);
  ierr = EPSSetFromOptions(eps);CHKERRQ(ierr);

  /* First solve */
  ierr = EPSSolve(eps);CHKERRQ(ierr);
  ierr = PetscPrintf(PETSC_COMM_WORLD," - - - First solve, default subspace dimension - - -\n");CHKERRQ(ierr);
  ierr = EPSErrorView(eps,EPS_ERROR_RELATIVE,NULL);CHKERRQ(ierr);

  /* Second solve */
  ierr = EPSGetDimensions(eps,&nev,&ncv,NULL);CHKERRQ(ierr);
  ierr = EPSSetDimensions(eps,nev,ncv+2,PETSC_DEFAULT);CHKERRQ(ierr);
  ierr = EPSSolve(eps);CHKERRQ(ierr);
  ierr = PetscPrintf(PETSC_COMM_WORLD," - - - Second solve, subspace of increased size - - -\n");CHKERRQ(ierr);
  ierr = EPSErrorView(eps,EPS_ERROR_RELATIVE,NULL);CHKERRQ(ierr);

  ierr = EPSDestroy(&eps);CHKERRQ(ierr);
  ierr = MatDestroy(&A);CHKERRQ(ierr);
  ierr = SlepcFinalize();
  return ierr;
}

/*TEST

   test:
      suffix: 1
      args: -n 18 -eps_type {{krylovschur arnoldi gd jd rqcg lobpcg lapack}} -eps_max_it 1500
      output_file: output/test20_1.out

   test:
      suffix: 1_lanczos
      args: -n 18 -eps_type lanczos -eps_lanczos_reorthog full -eps_max_it 1500
      output_file: output/test20_1.out

TEST*/
