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generic_cylinders.rst

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generic_cylinders.py

The program mpisppy.generic_cylinders.py provides a starting point for creating a customized program for processing a model or perhaps it will be all that is needed for a particular model. Not all mpi-sppy features are implemented in this program, but enough are to provide examples and to get started. A bash script to illustrate its use is examples.generic_cylinders.bash.

For a new model, you will need to create a python file that will be refered to as the module and/or the model file. The file must contain a :ref:`scenario_creator` and :ref:`helper_functions`. The file name is given without the the .py extension as the --module-name on the command and it should be the first argument. It is needed even with the --help argument, e.g.,

python ../mpisppy/generic_cylinders.py --module-name farmer/farmer --help

Note

If you want to run cylinders, you need to use mpiexec; however, if you are solving the EF directly, you do not need mpiexec.

Note

This functionality is at the level of alpha-release.

Pickled Scenarios

The generic_cylinders program supports pickling and unpickling scenarios. When pickling, all ranks are used for pickling, no other processing is done and command line arguments other than pickle-scenarios-dir are ignored.

Note

When unpickling, num_scens might be needed on cfg so num-scens is probably needed on the command line. Consistency with the files in the pickle directory might not be checked by the program.

A Class in the module

If you want to have a class in the module to provide helper functions, your module still needs to have an inparse_adder function and the module will need to have a function called get_mpisppy_helper_object(cfg) that returns the object. It is called by generic_cylinders.py after cfg is populated and can be used to create a class. Note that the function inparser_adder cannot make use of the class because that function is called before get_function_object.

The class definition needs to include all helper functions other than inparser_adder.

custom_writer

Advanced users might want to write their own solution output function. If the module contains a function called custom_writer(), it will be called at the end of processing. If you are writing such a function, you should look in generic_cylinders.py to see the two places it appears and the arguments that are passed from each place (your function can test the type of the first argument to see whence it was called or it can examine the call stack for more information).

Assuming the first formal parameter in your function is assigned to variable named wheel in the non-ef case, your function probably should include something along the lines of this:

.. code_block:: python

   if wheel.spcomm.opt.cylinder_rank == 0:

so that you avoid writing the output from every rank. Note this verification is automatically performed by WheelSpinner if you call your custom writer functions through wheel.write_first_stage_solution(solution_file_name, first_stage_solution_writer=my_first_stage_writer) and wheel.write_tree_solution(solution_dir_name, scenario_tree_solution_writer=my_tree_solution_writer).