A broadcast variable is any variable other
than the loop variable or a sliced variable that is not affected by
an assignment inside the loop. At the start of a parfor-loop,
the values of any broadcast variables are sent to all workers. Although
this type of variable can be useful or even essential, broadcast variables
that are large can cause a lot of communication between client and
workers. In some cases it might be more efficient to use temporary
variables for this purpose, creating and assigning them inside the
loop.