There are a number of concepts and terminologies that are useful to understand in order to use
disk.frame is a folder containing
fst files named “1.fst”, “2.fst”, “3.fst” etc. Each of the “.fst” file is called a chunk.
disk.frame is achieved using the
future package. When performing many tasks,
disk.frame uses multiple workers, where each worker is an R session, to perform the tasks in parallel.
It is recommended that you should run the following immediately after
library(disk.frame) to set-up multiple workers. For example:
For example, suppose we wish to compute the number of rows for each chunk, we can clearly perform this simultaneously in parallel. The code to do that is
or equivalent using the
Say there are
n chunks in
df, and there are
m workers. Then the first
m chunks will run
To see how many workers are at work, use
df %>% some_fn %>% collect is callled. The
some_fn is applied to each chunk of
df. The collect will row-bind the results from
some_fn(chunk)together if the returned value of
some_fn is a data.frame, or it will return a
list containing the results of
The session that receives these results is called the main session. In general, we should try to minimise the amount of data passed from the worker sessions back to the main session, because passing data around can be slow.
Also, please note that there is no communication between the workers, except for workers passing data back to the main session.