2: static char help[] = "Demonstrates using the PetscBag Object\n\n";

  4: /*T
  5:    Concepts: bags;
  6:    Processors: n
  7: T*/
 8:  #include petsc.h
 9:  #include petscbag.h

 11: /*
 12:   Enum variables can be stored in a bag but require a string array
 13:   to name their fields.  The fourth entry in this example is the name 
 14:   of the enum, the fifth is the prefix (none in this case), and the last 
 15:   entry is the null string.
 16: */
 17: typedef enum {
 18:   THIS = 0, THAT = 1, THE_OTHER = 2
 19: } YourChoice;
 20: const char *EnumeratedChoices[] = {"THIS","THAT","THE_OTHER","EnumeratedChoices","",0};

 22: /*
 23:   Data structures can be used in a bag as long as they 
 24:   are declared in the bag with a variable, not with a pointer.
 25: */
 26: typedef struct {
 27:   PetscReal   x1,x2;
 28: } TwoVec;

 30: /* 
 31:   Define a C struct that will contain my program's parameters.
 32: */
 33: typedef struct {
 34:   char          filename[PETSC_MAX_PATH_LEN];
 35:   PetscReal     rho;
 36:   PetscScalar   W;
 37:   PetscInt      Ii;
 38:   PetscTruth    T;
 39:   TwoVec        pos;
 40:   PetscDataType dt;
 41:   YourChoice    which;
 42: } Parameter;
 43: 

 47: int main(int argc,char **argv)
 48: {
 50:   PetscBag       bag;
 51:   Parameter      *params;
 52:   PetscViewer    viewer;

 54:   /*
 55:     Every PETSc routine should begin with the PetscInitialize() routine.
 56:     argc, argv - These command line arguments are taken to extract the options
 57:                  supplied to PETSc and options supplied to MPI.
 58:     help       - When PETSc executable is invoked with the option -help, 
 59:                  it prints the various options that can be applied at 
 60:                  runtime.  The user can use the "help" variable place
 61:                  additional help messages in this printout.
 62:   */
 63:   PetscInitialize(&argc,&argv,(char *)0,help);

 65:   /* Create an empty bag */
 66:   PetscBagCreate(PETSC_COMM_WORLD,sizeof(Parameter),&bag);
 67:   PetscBagGetData(bag,(void **)&params);

 69:   /* register variables, defaults, names, help strings */
 70:   PetscBagSetName(bag,"ParameterBag","contains parameters for simulations of top-secret, dangerous physics");
 71:   PetscBagRegisterString(bag,&params->filename,PETSC_MAX_PATH_LEN,"myfile","filename","Name of secret file");
 72:   PetscBagRegisterReal  (bag,&params->rho,3.0,"rho","Density, kg/m^3");
 73:   PetscBagRegisterScalar(bag,&params->W,  5.0,"W","Vertical velocity, m/sec");
 74:   PetscBagRegisterInt   (bag,&params->Ii, 2,"modes_x","Number of modes in x-direction");
 75:   PetscBagRegisterTruth (bag,&params->T,  PETSC_FALSE,"do_output","Write output file (yes/no)");
 76:   PetscBagRegisterEnum  (bag,&params->dt, PetscDataTypes,(PetscEnum)PETSC_INT,"dt","meaningless datatype");
 77:   PetscBagRegisterReal  (bag,&params->pos.x1,1.0,"x1","x position");
 78:   PetscBagRegisterReal  (bag,&params->pos.x2,1.9,"x2","y position");
 79:   PetscBagRegisterEnum  (bag,&params->which, EnumeratedChoices, (PetscEnum)THAT, "choose","Express yourself by choosing among enumerated things");

 81:   /* write bag to stdio & binary file */
 82:   PetscBagView(bag,PETSC_VIEWER_STDOUT_WORLD);
 83:   PetscViewerBinaryOpen(PETSC_COMM_WORLD,"binaryoutput",FILE_MODE_WRITE,&viewer);
 84:   PetscBagView(bag,viewer);
 85:   PetscViewerDestroy(viewer);
 86:   PetscBagDestroy(bag);

 88:   /* load bag from file & write to stdio */
 89:   PetscViewerBinaryOpen(PETSC_COMM_WORLD,"binaryoutput",FILE_MODE_READ,&viewer);
 90:   PetscBagLoad(viewer,&bag);
 91:   PetscViewerDestroy(viewer);
 92:   PetscBagView(bag,PETSC_VIEWER_STDOUT_WORLD);

 94:   /* reuse the parameter struct */
 95:   PetscBagGetData(bag,(void**)&params);
 96:   PetscPrintf(PETSC_COMM_WORLD,"The value of rho after loading is: %f\n",params->rho);

 98:   /* clean up and exit */
 99:   PetscBagDestroy(bag);
100:   PetscFinalize();
101:   return 0;
102: }