By default, each function step is executed just after the previous one is fully completed. If you would like to execute any steps on parallel you have to add an extra parameter called prerequisites. This parameters will identify the dependent id, i.e. the id of the previous step which has to be completed before executing this step.
Here you can see an example which tries to illustrate how to create a parallel step:
getBestVolumes is executed just after the previous step is completed.
On the other hand,
reconstruct is executed _numVolumes_ times. All
these executions are performed on parallel because they only depend on
bestVolumesStepId (id of the
getBestVolumes function). If we do not
prerequisites parameter, each
would depend on the previous
reconstruct execution and therefore they
would not be executed in parallel.
TO DO: mention how to use something like this is in `_defineParams`: