Actual source code: ex25.c

petsc-3.7.3 2016-07-24
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  1: static char help[] = "Tests CG, MINRES and SYMMLQ on the symmetric indefinite matrices: afiro \n\n";

  3: #include <petscksp.h>

  7: int main(int argc,char **args)
  8: {
  9:   Mat            C;
 10:   PetscScalar    none = -1.0;
 11:   PetscMPIInt    rank,size;
 13:   PetscInt       its,k;
 14:   PetscReal      err_norm,res_norm;
 15:   Vec            x,b,u,u_tmp;
 16:   PC             pc;
 17:   KSP            ksp;
 18:   PetscViewer    view;
 19:   char           filein[128];     /* input file name */

 21:   PetscInitialize(&argc,&args,(char*)0,help);
 22:   MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
 23:   MPI_Comm_size(PETSC_COMM_WORLD,&size);

 25:   /* Load the binary data file "filein". Set runtime option: -f filein */
 26:   PetscPrintf(PETSC_COMM_WORLD,"\n Load dataset ...\n");
 27:   PetscOptionsGetString(NULL,NULL,"-f",filein,128,NULL);
 28:   PetscViewerBinaryOpen(PETSC_COMM_WORLD,filein,FILE_MODE_READ,&view);
 29:   MatCreate(PETSC_COMM_WORLD,&C);
 30:   MatSetType(C,MATMPISBAIJ);
 31:   MatLoad(C,view);
 32:   VecCreate(PETSC_COMM_WORLD,&b);
 33:   VecCreate(PETSC_COMM_WORLD,&u);
 34:   VecLoad(b,view);
 35:   VecLoad(u,view);
 36:   PetscViewerDestroy(&view);
 37:   /* VecView(b,VIEWER_STDOUT_WORLD); */
 38:   /* MatView(C,VIEWER_STDOUT_WORLD); */

 40:   VecDuplicate(u,&u_tmp);

 42:   /* Check accuracy of the data */
 43:   /*
 44:   MatMult(C,u,u_tmp);
 45:   VecAXPY(u_tmp,none,b);
 46:   VecNorm(u_tmp,NORM_2,&res_norm);
 47:   PetscPrintf(PETSC_COMM_WORLD,"Accuracy of the loading data: | b - A*u |_2 : %g \n",(double)res_norm);
 48:   */

 50:   /* Setup and solve for system */
 51:   VecDuplicate(b,&x);
 52:   for (k=0; k<3; k++) {
 53:     if (k == 0) {                              /* CG  */
 54:       KSPCreate(PETSC_COMM_WORLD,&ksp);
 55:       KSPSetType(ksp,KSPCG);
 56:       KSPSetOperators(ksp,C,C);
 57:       PetscPrintf(PETSC_COMM_WORLD,"\n CG: \n");
 58:     } else if (k == 1) {                       /* MINRES */
 59:       KSPCreate(PETSC_COMM_WORLD,&ksp);
 60:       KSPSetType(ksp,KSPMINRES);
 61:       KSPSetOperators(ksp,C,C);
 62:       PetscPrintf(PETSC_COMM_WORLD,"\n MINRES: \n");
 63:     } else {                                 /* SYMMLQ */
 64:       KSPCreate(PETSC_COMM_WORLD,&ksp);
 65:       KSPSetOperators(ksp,C,C);
 66:       KSPSetType(ksp,KSPSYMMLQ);
 67:       PetscPrintf(PETSC_COMM_WORLD,"\n SYMMLQ: \n");
 68:     }

 70:     KSPGetPC(ksp,&pc);
 71:     PCSetType(pc,PCNONE);

 73:     /*
 74:     Set runtime options, e.g.,
 75:         -ksp_type <type> -pc_type <type> -ksp_monitor -ksp_rtol <rtol>
 76:                          -pc_type jacobi -pc_jacobi_type rowmax
 77:     These options will override those specified above as long as
 78:     KSPSetFromOptions() is called _after_ any other customization routines.
 79:     */
 80:     KSPSetFromOptions(ksp);

 82:     /* Solve linear system; */
 83:     KSPSolve(ksp,b,x);
 84:     KSPGetIterationNumber(ksp,&its);

 86:     /* Check error */
 87:     VecCopy(u,u_tmp);
 88:     VecAXPY(u_tmp,none,x);
 89:     VecNorm(u_tmp,NORM_2,&err_norm);
 90:     MatMult(C,x,u_tmp);
 91:     VecAXPY(u_tmp,none,b);
 92:     VecNorm(u_tmp,NORM_2,&res_norm);

 94:     PetscPrintf(PETSC_COMM_WORLD,"Number of iterations = %3d\n",its);
 95:     PetscPrintf(PETSC_COMM_WORLD,"Residual norm: %g;",(double)res_norm);
 96:     PetscPrintf(PETSC_COMM_WORLD,"  Error norm: %g.\n",(double)err_norm);

 98:     KSPDestroy(&ksp);
 99:   }

101:   /*
102:        Free work space.  All PETSc objects should be destroyed when they
103:        are no longer needed.
104:   */
105:   VecDestroy(&b);
106:   VecDestroy(&u);
107:   VecDestroy(&x);
108:   VecDestroy(&u_tmp);
109:   MatDestroy(&C);

111:   PetscFinalize();
112:   return 0;
113: }