Parallel Programming with O2scl¶

Parallel contents¶

Thread safety and parallelism
OpenMP and O2scl
MPI and O2scl

Thread safety and parallelism¶

Generally, O₂scl objects are thread-safe in the same way that classes like std::vector<double> are thread-safe: reads are safe and writes are unsafe. It may be useful to make objects const to ensure that one is reading data in a thread-safe way. O₂scl is designed to ensure const methods are thread-safe, unless noted. (A few classes contain mutable internal members which mean that const methods are not thread-safe, and this is noted in the class documentation.)

OpenMP and O2scl¶

OpenMP support may be enabled during installation by --enable-openmp. OpenMP support during installation allows O₂scl to use parallelism to speed up some table functions and to test the multithreaded behavior of anneal_para, mcmc_para_base, and mcmc_para_table.

On some systems, code similar to the following may be required to ensure that the error handler is valid on each OpenMP thread:

int main(int argc, char *argv[]) {
  cout.setf(ios::scientific);
  MPI_Init(&argc,&argv);
  // Create a new error handler for this thread
  o2scl::err_hnd_cpp ee;
  o2scl::err_hnd=&ee;
  // Do stuff here
  MPI_Finalize();
  return 0;
}

You can test to see if OpenMP support was enabled during installation in the o2scl::o2scl_settings object of type lib_settings_class or with acol -v.

MPI and O2scl¶

Currently, all MPI calls are in header classes, except for some support for parallel HDF5 which is currently being developed and not yet enabled. MPI functions are used in anneal_para, mcmc_para_base, and mcmc_para_table.

You can test to see if MPI support was enabled during installation in the ref o2scl::o2scl_settings object of type ref o2scl::lib_settings_class or with acol -v.