Global variables

Global variables available

All global entities for the ChiTech library are contained within the static chi class. This class has the name chi and an instance of it cannot be created. Within this class, all of its members are statically declared. Several singleton objects are defined in chi, they are:

• chi::mpi A handler for parallel related items.
• chi::program_timer The primary program timer.
• chi::console The link to the lua scripting engine.
• chi::log A handler for parallel logging events and verbosity.

A number of stacks are also declared. They are basically arrays of shared pointers (i.e., std::shared_ptr)

There are also a number of secondary global variables that assist developers with coding. They are:

• chi::run_time::input_file_name Holds the input file name if supplied.
• chi::run_time::termination_posted A flag used during interactive mode.
• chi::run_time::sim_option_interactive A flag indicating whether the code is run in interactive mode.
• chi::run_time::allow_petsc_error_handler A flag indicating whether the allow the native PETSC error handler.

Connecting to the global data block

The stack items stored within chi can be accessed either by reference or as a std::shared_ptr. The two functions that facilitate this are as follows:

#include "chi_runtime.h"
#include "mesh/SurfaceMesh/chi_surfacemesh.h" //Just an example
 
void SomeFunction()
{
  int handle = 2;
  auto& chi::GetStackItem<chi_mesh::SurfaceMeshPtr>(chi::surface_mesh_stack,
                                                    handle);
  //or
  auto chi::GetStackItemPtr<chi_mesh::SurfaceMeshPtr>(chi::surface_mesh_stack,
                                                      handle);
}

There are multiple stacks, currently (which might not be still accurate):

chi::meshhandler_stack;
chi::surface_mesh_stack;
chi::logicvolume_stack;
chi::field_func_interpolation_stack;
chi::unpartitionedmesh_stack;
chi::solver_stack;
chi::material_stack;
chi::trnsprt_xs_stack;
chi::fieldfunc_stack;
chi::quadrature_stack;
chi::angular_quadrature_stack;

Connecting to MPI

General MPI information like the current location id and the total amount of parallel processes is contained in CHI_MPI:

• chi_objects::MPI_Info::location_id
• chi_objects::MPI_Info::process_count

Additionally, by including the headers for chi_mpi, developers have access to all the classic mpi headers.

#include "chi_runtime.h"
#include "chi_mpi.h"
 
if (chi::mpi.location_id == 1)
 printf("This is process 1, Dab!");

Connecting to the parallel logging utility

Printing information in a parallel environment can be a very involved process. One can't simply use std::cout << on every process otherwise the output to the log will be chaotic. For this reason we employ a common logging utility which returns an output string-stream using the function call ChiLog::Log.

Connecting to chi::log is done as follows

#include "chi_runtime.h"
#include "chi_log.h"
 
void Function()
{
    chi::log.Log() << "Hello from location 0";
    chi::log.LogAll() << "Hello from all locations";
}

The logger has calls of differing verbosity:

• chi_objects::ChiLog::Log0(), Used only for location 0
• chi_objects::ChiLog::Log0Warning(), Warning only for location 0
• chi_objects::ChiLog::Log0Error(), Error only for location 0
• chi_objects::ChiLog::Log0Verbose0(), Default verbosity level
• chi_objects::ChiLog::Log0Verbose1(), Used only if verbosity level equals 1
• chi_objects::ChiLog::Log0Verbose2(), Used only if verbosity level equals 2
• chi_objects::ChiLog::LogAll(), Verbose level 0 all locations
• chi_objects::ChiLog::LogAllWarning(), Warning for any location
• chi_objects::ChiLog::LogAllError(), Error for any location
• chi_objects::ChiLog::LogAllVerbose0(), Default verbosity level
• chi_objects::ChiLog::LogAllVerbose1(), Used only if verbosity level equals 1
• chi_objects::ChiLog::LogAllVerbose2(), Used only if verbosity level equals 2

Todo:

Commandline parameter documentation