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.