Callback functions

Detailed Description

Obtaining intermediate results as fast as possible.

The primary way of obtaining the result(s) of an integration is by waiting for the integration to finish and inspecting the return value of the integrator. However, usually the integration is subdivided into a number of smaller iterations, each of which are available much faster than the final combined result. Therefore callback function provide a secondary way of obtaining the intermediate results as soon as possible. The integrator simply calls this callback function with a newly created checkpoint that contains the results of the recently finished iterations and all of the iterations before, together with the random number generators, which were used to calculate the results.

Each callback function must accept the appropriate checkpoint, for example, in the case of VEGAS a vegas_chkpt. In the case of MPI-parallelized integration routines the first argument must be instead the the communicator and the second one the checkpoint.

Finally, the callback function must return a boolean that signals whether the remaining iterations should be performed or not. Returning false can used to implement a callback function which stop the integrator when a certain level of precision is reached, see vegas_stop_after_precision.cpp for an example how to implement this.

This library comes with two predefined callback function types, callback and mpi_callback, which are used for every integration algorithm and their parallelised counterparts, respectively.

Classes
class	hep::callback< Checkpoint >
class	hep::mpi_callback< Checkpoint >

Enumerations
enum	hep::callback_mode { hep::callback_mode::silent, hep::callback_mode::silent_and_write_chkpt, hep::callback_mode::verbose, hep::callback_mode::verbose_and_write_chkpt }

Enumeration Type Documentation

callback_mode

enum hep::callback_mode

strong

Enumeration determining the behaviour of callback::operator()().

Enumerator
silent	Do not print any messages after each iteration and do not save checkpoints to disk.
silent_and_write_chkpt	Do not print any messages after each iteration, but save checkpoints to disk.
verbose	Print a detailed message after each iteration, but do not write checkpoints to disk.
verbose_and_write_chkpt	Same as callback_mode::verbose, but also writes checkpoints to disk.