2: /* Program usage:  mpirun -np <procs> ex2 [-help] [all PETSc options] */

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

  6: /*T
  7:    Concepts: Low rank correction

  9:    Processors: n
 10: T*/

 12:  #include petscmat.h

 16: int main(int argc,char **args)
 17: {
 18:   Vec            x,b;
 19:   Mat            A,U,V,LR;
 20:   PetscInt       i,j,Ii,J,Istart,Iend,m = 8,n = 7,rstart,rend;
 22:   PetscTruth     flg;
 23:   PetscScalar    *u,a;

 25:   PetscInitialize(&argc,&args,(char *)0,help);
 26:   PetscOptionsGetInt(PETSC_NULL,"-m",&m,PETSC_NULL);
 27:   PetscOptionsGetInt(PETSC_NULL,"-n",&n,PETSC_NULL);

 29:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
 30:          Create the sparse matrix
 31:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 32:   MatCreate(PETSC_COMM_WORLD,&A);
 33:   MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,m*n,m*n);
 34:   MatSetFromOptions(A);
 35:   MatGetOwnershipRange(A,&Istart,&Iend);
 36:   for (Ii=Istart; Ii<Iend; Ii++) {
 37:     a = -1.0; i = Ii/n; j = Ii - i*n;
 38:     if (i>0)   {J = Ii - n; MatSetValues(A,1,&Ii,1,&J,&a,INSERT_VALUES);}
 39:     if (i<m-1) {J = Ii + n; MatSetValues(A,1,&Ii,1,&J,&a,INSERT_VALUES);}
 40:     if (j>0)   {J = Ii - 1; MatSetValues(A,1,&Ii,1,&J,&a,INSERT_VALUES);}
 41:     if (j<n-1) {J = Ii + 1; MatSetValues(A,1,&Ii,1,&J,&a,INSERT_VALUES);}
 42:     a = 4.0; MatSetValues(A,1,&Ii,1,&Ii,&a,INSERT_VALUES);
 43:   }
 44:   MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
 45:   MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);

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


 65:   MatCreate(PETSC_COMM_WORLD,&V);
 66:   MatSetSizes(V,PETSC_DECIDE,PETSC_DECIDE,m*n,3);
 67:   MatSetType(V,MATDENSE);
 68:   MatGetOwnershipRange(U,&rstart,&rend);
 69:   MatGetArray(V,&u);
 70:   for (i=rstart; i<rend; i++) {
 71:     u[i-rstart]          = (PetscReal)i;
 72:     u[i+rend-2*rstart]   = (PetscReal)1.2*i;
 73:     u[i+2*rend-3*rstart] = (PetscReal)1.67*i+2;
 74:   }
 75:   MatRestoreArray(V,&u);
 76:   MatAssemblyBegin(V,MAT_FINAL_ASSEMBLY);
 77:   MatAssemblyEnd(V,MAT_FINAL_ASSEMBLY);
 78:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
 79:          Create low rank created matrix
 80:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 81:   MatCreateLRC(A,U,V,&LR);

 83:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
 84:          Create test vectors
 85:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 86:   VecCreate(PETSC_COMM_WORLD,&x);
 87:   VecSetSizes(x,PETSC_DECIDE,m*n);
 88:   VecSetFromOptions(x);
 89:   VecDuplicate(x,&b);
 90:   VecGetOwnershipRange(x,&rstart,&rend);
 91:   VecGetArray(x,&u);
 92:   for (i=rstart; i<rend; i++) u[i-rstart] = (PetscScalar)i;
 93:   VecRestoreArray(x,&u);

 95:   MatMult(LR,x,b);
 96:   /*
 97:      View the product if desired
 98:   */
 99:   PetscOptionsHasName(PETSC_NULL,"-view_product",&flg);
100:   if (flg) {VecView(b,PETSC_VIEWER_STDOUT_WORLD);}

102:   VecDestroy(x);
103:   VecDestroy(b);
104:   /* you can destroy the matrices in any order you like */
105:   MatDestroy(A);
106:   MatDestroy(U);
107:   MatDestroy(V);
108:   MatDestroy(LR);

110:   /*
111:      Always call PetscFinalize() before exiting a program.  This routine
112:        - finalizes the PETSc libraries as well as MPI
113:        - provides summary and diagnostic information if certain runtime
114:          options are chosen (e.g., -log_summary). 
115:   */
116:   PetscFinalize();
117:   return 0;
118: }