addingtasks.rst

How to add a new task to SWIFT?

This tutorial will step through how to add a new task to swift. First we will go through the idealology of adding a new task to SWIFT. This will be followed by an example of how to add a task for an imposed external gravitational field to SWIFT and a task to include "cooling" to the gas particles.

In the simplest case adding a new tasks requires changes to five files, namely:

• task.h
• cell.h
• timers.h
• task.c
• engine.c

Further, implementation details of what the task will then do should be added to another file (for example runner_myviptask.c) which will contain the actual task implementation.

So now lets look at what needs to change in each of the files above, starting with task.h

task.h

Within task.h there exists a structure of the form:

/* The different task types. */
enum task_types {
    task_type_none = 0,
    task_type_sort,
    task_type_self,
    task_type_pair,
          .
          .
          .
    task_type_my_new_task,
    task_type_psort,
    task_type_split_cell,
    task_type_count
};

Within this task structure your new task should be added. Add the task entry anywhere in the struct before the task_type_count member. This last entry is used to count the number of tasks and must always be the last entry.

task.c

Within task.c the addition of the new task type must be include in a character list (which at the moment is only used for debugging purposes):

/* Task type names. */
const char *taskID_names[task_type_count] = {
"none",  "sort",    "self",    "pair",    "sub",
"ghost", "kick1",   "kick2",   "send",    "recv",
"link",  "grav_pp", "grav_mm", "grav_up", "grav_down",
"my_new_task", "psort", "split_cell"};

The new task type should be added to this list in the same order as it was added within the task_types struct in task.h

cell.h

cell.h contains pointers to all of the tasks associated with that cell. You must include your new task type here e.g:

struct task *my_new_task;