# Glossary

task

  A stage in a computational pipeline.

  Each task in ruffus is represented by a python function.

  For example, a task might be to find the products of a sets of two numbers:

      4 x 5 = 20
      5 x 6 = 30
      2 x 7 = 14

job

  Any number of operations which can be run in parallel and make up the work in a stage of a computional pipeline.

  Each task in ruffus is a separate call to the task function.

  For example, if a task is to find products of numbers, each of these will be a separate job.

  > Job1:

  >     4 x 5 = 20

  > Job2:

  >     5 x 6 = 30

  > Job3:

  >     2 x 7 = 14

  Jobs need not complete in order.

decorator

  Ruffus decorators allow functions to be incorporated into a computational pipeline, with automatic generation of parameters, dependency checking etc., without modifying any code within the function. Quoting from the python wiki:

  > A Python decorator is a specific change to the Python syntax that allows us to more conveniently alter functions and methods.

  > Decorators dynamically alter the functionality of a function, method, or class without having to directly use subclasses or change the source code of the function being decorated.

generator

  python generators are new to python 2.2 (see Charming Python: Iterators and simple generators). They allow iterable data to be generated on the fly.

  Ruffus asks for generators when you want to generate job parameters dynamically.

  Each set of job parameters is returned by the `yield` keyword for greater clarity. For example,:

      def generate_job_parameters():

          for file_index, file_name in iterate(all_file_names):

              # parameter for each job
              yield file_index, file_name

  Each job takes the parameters `file_index` and `file_name`