A broadcast variable is any variable, other
than the loop variable or a sliced variable, that does not change
inside the loop. At the start of a parfor-loop,
the values of any broadcast variables are sent to all workers. This
type of variable can be useful or even essential for particular tasks.
However, large broadcast variables can cause significant communication
between client and workers and increase parallel overhead. Sometimes
it is more efficient to use temporary variables for this purpose,
creating and assigning them inside the loop.
For more details, see Temporary Variables and Deciding When to Use parfor.