1: /*
  2:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  3:    SLEPc - Scalable Library for Eigenvalue Problem Computations
  4:    Copyright (c) 2002-, Universitat Politecnica de Valencia, Spain

  6:    This file is part of SLEPc.
  7:    SLEPc is distributed under a 2-clause BSD license (see LICENSE).
  8:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  9: */

 11: static char help[] = "Eigenproblem for the 1-D Laplacian with constraints. "
 12:   "Based on ex1.\n"
 13:   "The command line options are:\n"
 14:   "  -n <n>, where <n> = number of grid subdivisions = matrix dimension.\n\n";

 16: #include <slepceps.h>

 18: int main(int argc,char **argv)
 19: {
 20:   Mat            A;
 21:   EPS            eps;
 22:   EPSType        type;
 23:   Vec            *vi=NULL,*vc=NULL,t;
 24:   PetscInt       n=30,nev=4,i,j,Istart,Iend,nini=0,ncon=0,bs;
 25:   PetscReal      alpha,beta,restart;
 26:   PetscBool      flg,lock;

 28:   PetscFunctionBeginUser;
 29:   PetscCall(SlepcInitialize(&argc,&argv,NULL,help));
 30:   PetscCall(PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL));
 31:   PetscCall(PetscOptionsGetInt(NULL,NULL,"-nini",&nini,NULL));
 32:   PetscCall(PetscOptionsGetInt(NULL,NULL,"-ncon",&ncon,NULL));
 33:   PetscCall(PetscPrintf(PETSC_COMM_WORLD,"\n1-D Laplacian Eigenproblem, n=%" PetscInt_FMT " nini=%" PetscInt_FMT " ncon=%" PetscInt_FMT "\n\n",n,nini,ncon));

 35:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 36:      Compute the operator matrix that defines the eigensystem, Ax=kx
 37:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 39:   PetscCall(MatCreate(PETSC_COMM_WORLD,&A));
 40:   PetscCall(MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,n,n));
 41:   PetscCall(MatSetFromOptions(A));

 43:   PetscCall(MatGetOwnershipRange(A,&Istart,&Iend));
 44:   for (i=Istart;i<Iend;i++) {
 45:     if (i>0) PetscCall(MatSetValue(A,i,i-1,-1.0,INSERT_VALUES));
 46:     if (i<n-1) PetscCall(MatSetValue(A,i,i+1,-1.0,INSERT_VALUES));
 47:     PetscCall(MatSetValue(A,i,i,2.0,INSERT_VALUES));
 48:   }
 49:   PetscCall(MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY));
 50:   PetscCall(MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY));

 52:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 53:                 Create the eigensolver and set various options
 54:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 55:   PetscCall(EPSCreate(PETSC_COMM_WORLD,&eps));
 56:   PetscCall(EPSSetOperators(eps,A,NULL));
 57:   PetscCall(EPSSetProblemType(eps,EPS_HEP));
 58:   PetscCall(EPSSetType(eps,EPSLOBPCG));
 59:   PetscCall(EPSSetWhichEigenpairs(eps,EPS_SMALLEST_REAL));
 60:   PetscCall(EPSSetConvergenceTest(eps,EPS_CONV_ABS));
 61:   PetscCall(EPSSetDimensions(eps,nev,PETSC_DETERMINE,PETSC_DETERMINE));
 62:   PetscCall(EPSLOBPCGSetBlockSize(eps,nev));
 63:   PetscCall(EPSLOBPCGSetRestart(eps,0.7));
 64:   PetscCall(EPSSetTolerances(eps,1e-8,1200));
 65:   PetscCall(EPSSetFromOptions(eps));

 67:   PetscCall(MatCreateVecs(A,&t,NULL));
 68:   if (nini) {
 69:     PetscCall(VecDuplicateVecs(t,nini,&vi));
 70:     for (i=0;i<nini;i++) PetscCall(VecSetRandom(vi[i],NULL));
 71:     PetscCall(EPSSetInitialSpace(eps,nini,vi));
 72:   }
 73:   if (ncon) {   /* constraints are exact eigenvectors of lowest eigenvalues */
 74:     alpha = PETSC_PI/(n+1);
 75:     beta  = PetscSqrtReal(2.0/(n+1));
 76:     PetscCall(VecDuplicateVecs(t,ncon,&vc));
 77:     for (i=0;i<ncon;i++) {
 78:       for (j=0;j<n;j++) PetscCall(VecSetValue(vc[i],j,PetscSinReal(alpha*(j+1)*(i+1))*beta,INSERT_VALUES));
 79:       PetscCall(VecAssemblyBegin(vc[i]));
 80:       PetscCall(VecAssemblyEnd(vc[i]));
 81:     }
 82:     PetscCall(EPSSetDeflationSpace(eps,ncon,vc));
 83:   }

 85:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 86:                       Solve the eigensystem
 87:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 89:   PetscCall(EPSSolve(eps));
 90:   PetscCall(EPSGetType(eps,&type));
 91:   PetscCall(PetscPrintf(PETSC_COMM_WORLD," Solution method: %s\n",type));
 92:   PetscCall(PetscObjectTypeCompare((PetscObject)eps,EPSLOBPCG,&flg));
 93:   if (flg) {
 94:     PetscCall(EPSLOBPCGGetLocking(eps,&lock));
 95:     if (lock) PetscCall(PetscPrintf(PETSC_COMM_WORLD," Using soft locking\n"));
 96:     PetscCall(EPSLOBPCGGetRestart(eps,&restart));
 97:     PetscCall(PetscPrintf(PETSC_COMM_WORLD," LOBPCG Restart parameter=%.4g\n",(double)restart));
 98:     PetscCall(EPSLOBPCGGetBlockSize(eps,&bs));
 99:     PetscCall(PetscPrintf(PETSC_COMM_WORLD," LOBPCG Block size=%" PetscInt_FMT "\n",bs));
100:   }

102:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
103:                     Display solution and clean up
104:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

106:   PetscCall(EPSErrorView(eps,EPS_ERROR_RELATIVE,NULL));
107:   PetscCall(EPSDestroy(&eps));
108:   PetscCall(MatDestroy(&A));
109:   PetscCall(VecDestroyVecs(nini,&vi));
110:   PetscCall(VecDestroyVecs(ncon,&vc));
111:   PetscCall(VecDestroy(&t));
112:   PetscCall(SlepcFinalize());
113:   return 0;
114: }

116: /*TEST

118:    testset:
119:       args: -ncon 2
120:       output_file: output/test24_1.out
121:       test:
122:          suffix: 1
123:          requires: !single
124:       test:
125:          suffix: 1_cuda
126:          args: -mat_type aijcusparse
127:          requires: cuda !single
128:       test:
129:          suffix: 1_hip
130:          args: -mat_type aijhipsparse
131:          requires: hip !single

133: TEST*/