2: static char help[] = "Tests MatCreateLRC()\n\n";

  4: /*T
  5:    Concepts: Low rank correction

  7:    Processors: n
  8: T*/

 10:  #include <petscmat.h>

 12: int main(int argc,char **args)
 13: {
 14:   Vec            x,b,c=NULL;
 15:   Mat            A,U,V,LR;
 16:   PetscInt       i,j,Ii,J,Istart,Iend,m = 8,n = 7,rstart,rend;
 18:   PetscBool      flg;
 19:   PetscScalar    *u,a;

 21:   PetscInitialize(&argc,&args,(char*)0,help);if (ierr) return ierr;
 22:   PetscOptionsGetInt(NULL,NULL,"-m",&m,NULL);
 23:   PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);

 25:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 26:          Create the sparse matrix
 27:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 28:   MatCreate(PETSC_COMM_WORLD,&A);
 29:   MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,m*n,m*n);
 30:   MatSetFromOptions(A);
 31:   MatSetUp(A);
 32:   MatGetOwnershipRange(A,&Istart,&Iend);
 33:   for (Ii=Istart; Ii<Iend; Ii++) {
 34:     a = -1.0; i = Ii/n; j = Ii - i*n;
 35:     if (i>0)   {J = Ii - n; MatSetValues(A,1,&Ii,1,&J,&a,INSERT_VALUES);}
 36:     if (i<m-1) {J = Ii + n; MatSetValues(A,1,&Ii,1,&J,&a,INSERT_VALUES);}
 37:     if (j>0)   {J = Ii - 1; MatSetValues(A,1,&Ii,1,&J,&a,INSERT_VALUES);}
 38:     if (j<n-1) {J = Ii + 1; MatSetValues(A,1,&Ii,1,&J,&a,INSERT_VALUES);}
 39:     a = 4.0; MatSetValues(A,1,&Ii,1,&Ii,&a,INSERT_VALUES);
 40:   }
 41:   MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
 42:   MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);

 44:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 45:          Create the dense matrices
 46:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 47:   MatCreate(PETSC_COMM_WORLD,&U);
 48:   MatSetSizes(U,PETSC_DECIDE,PETSC_DECIDE,m*n,3);
 49:   MatSetType(U,MATDENSE);
 50:   MatSetUp(U);
 51:   MatGetOwnershipRange(U,&rstart,&rend);
 52:   MatDenseGetArray(U,&u);
 53:   for (i=rstart; i<rend; i++) {
 54:     u[i-rstart]          = (PetscReal)i;
 55:     u[i+rend-2*rstart]   = (PetscReal)1000*i;
 56:     u[i+2*rend-3*rstart] = (PetscReal)100000*i;
 57:   }
 58:   MatDenseRestoreArray(U,&u);
 59:   MatAssemblyBegin(U,MAT_FINAL_ASSEMBLY);
 60:   MatAssemblyEnd(U,MAT_FINAL_ASSEMBLY);

 62:   MatCreate(PETSC_COMM_WORLD,&V);
 63:   MatSetSizes(V,PETSC_DECIDE,PETSC_DECIDE,m*n,3);
 64:   MatSetType(V,MATDENSE);
 65:   MatSetUp(V);
 66:   MatGetOwnershipRange(U,&rstart,&rend);
 67:   MatDenseGetArray(V,&u);
 68:   for (i=rstart; i<rend; i++) {
 69:     u[i-rstart]          = (PetscReal)i;
 70:     u[i+rend-2*rstart]   = (PetscReal)1.2*i;
 71:     u[i+2*rend-3*rstart] = (PetscReal)1.67*i+2;
 72:   }
 73:   MatDenseRestoreArray(V,&u);
 74:   MatAssemblyBegin(V,MAT_FINAL_ASSEMBLY);
 75:   MatAssemblyEnd(V,MAT_FINAL_ASSEMBLY);

 77:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 78:          Create a vector to hold the diagonal of C
 79:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 80:   PetscOptionsHasName(NULL,NULL,"-use_c",&flg);
 81:   if (flg) {
 82:     VecCreateSeq(PETSC_COMM_SELF,3,&c);
 83:     VecGetArray(c,&u);
 84:     u[0] = 2.0;
 85:     u[1] = -1.0;
 86:     u[2] = 1.0;
 87:     VecRestoreArray(c,&u);
 88:   }

 90:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 91:          Create low rank correction matrix
 92:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 93:   PetscOptionsHasName(NULL,NULL,"-low_rank",&flg);
 94:   if (flg) {
 95:     /* create a low-rank matrix, with no A-matrix */
 96:     MatCreateLRC(NULL,U,c,V,&LR);
 97:   } else {
 98:     MatCreateLRC(A,U,c,V,&LR);
 99:   }

101:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
102:          Create test vectors
103:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
104:   VecCreate(PETSC_COMM_WORLD,&x);
105:   VecSetSizes(x,PETSC_DECIDE,m*n);
106:   VecSetFromOptions(x);
107:   VecDuplicate(x,&b);
108:   VecGetOwnershipRange(x,&rstart,&rend);
109:   VecGetArray(x,&u);
110:   for (i=rstart; i<rend; i++) u[i-rstart] = (PetscScalar)i;
111:   VecRestoreArray(x,&u);

113:   MatMult(LR,x,b);
114:   /*
115:      View the product if desired
116:   */
117:   PetscOptionsHasName(NULL,NULL,"-view_product",&flg);
118:   if (flg) {VecView(b,PETSC_VIEWER_STDOUT_WORLD);}

120:   VecDestroy(&x);
121:   VecDestroy(&b);
122:   /* you can destroy the matrices in any order you like */
123:   MatDestroy(&A);
124:   MatDestroy(&U);
125:   MatDestroy(&V);
126:   VecDestroy(&c);
127:   MatDestroy(&LR);

129:   /*
130:      Always call PetscFinalize() before exiting a program.  This routine
131:        - finalizes the PETSc libraries as well as MPI
132:        - provides summary and diagnostic information if certain runtime
133:          options are chosen (e.g., -log_view).
134:   */
135:   PetscFinalize();
136:   return ierr;
137: }