ygm::utility module reference

The utility namespace contains multiple components that often helpful when using YGM, but may not be necessary to use. Their uses include tracking the performance of YGM, getting easy access to basic functionality built on MPI_COMM_WORLD, and sending messages using YGM that contain specialized data types. The headers containing this functionality can be safely included in user programs, but is often already included in other YGM headers because they can be used within YGM.

ygm::utility::timer

The ygm::utility::timer class starts a very simple timer using MPI_Wtime. It includes elapsed() and reset() methods for checking the time since the timer has been started and resetting the start time of a timer, respectively.

Typical use of the ygm::utility::timer is:

ygm::utility::timer t{};
{
  // Do stuff
}
world.barrier();
world.cout0("Time: ", t.elapsed());

ygm::utility::progress_indicator

The ygm::utility::progress_indicator asynchronously tracks progress through a calculation across all processes, with each process periodically sending updates that are printed by rank 0. The progress_indicator prints the total number of work items completed and the rate at which they are completing.

The async_inc() method of the progress_indicator is used to locally indicate when work is progressing. This call will begin a nonblocking reduction when enough work has been completed to collect the output for printing. An internal progress_indicator::options class is used to control the message for printing and the frequency with which reductions and printing occurs.

Typical use of the ygm::utility::timer is:

ygm::utilijty::progress_indicator prog(world, {.update_freq = 10, .message = "Doing stuff"});
for (int i=0; i<1000; ++i) {
 prog.async_inc();
 // Do work
}
prog.complete();
world.barrier();

Global World Functionality

YGM provides the following functions for basic interactions with MPI_COMM_WORLD that can be done from anywhere within a YGM program:

  • ygm::wrank() - returns the current process’s rank

  • ygm::wrank0() - returns a boolean indicating whether the current rank is rank 0 or not

  • ygm::wsize() - returns the number of ranks in MPI_COMM_WORLD

  • ygm::wcout0() - prints output to std::cout from only rank 0

  • ygm::wcerr0() - same as ygm::wcout0() but provides std::cerr access for just rank 0

  • ygm::wcout() - prints output to std::cout from the current rank with its rank prepended

  • ygm::wcerr() - same as ygm::wcout() but prints to std::cerr

The printing functionality can be used either to get access to an output stream for printing or as a print() type of function, that is ygm::wcout0() << “Printint output” and ygm::wcout0(“Printing output”) will produce the same output.

Asserts

assert.hpp provides a small number of assert macros:

  • YGM_ASSERT_MPI - used for wrapping MPI calls to detect when MPI does not return MPI_SUCCESS

  • YGM_ASSERT_DEBUG - same functionality as assert

  • YGM_ASSERT_RELEASE - assert statement that is triggered even if NDEBUG is defined

Specialized Serialization Functions

A number of headers are provided for serialization of datatypes for communication through YGM:

  • boost_*.hpp - serialization for various Boost types

Utility Class Documentation

Utility Classes: