There's more...

The Bash & operand works well for a small number of tasks. If you had a hundred files to checksum, the script would try to start a hundred processes and might force your system into swapping, which would make the tasks run slower.

The GNU parallel command is not part of all installations, but again it can be loaded with your package manager. The parallel command optimizes the use of your resources without overloading any of them.

The parallel command reads a list of files on stdin and uses options similar to the find command's -exec argument to process these files. The {} symbol represents the file to be processed, and the {.} symbol represents the filename without a suffix.

The following command uses Imagemagick's convert command to make new, resized images of all the images in a folder:

ls *jpg | parallel convert {} -geometry 50x50 {.}Small.jpg