3.6 Parallel execution

The lilypond-book script cannot be used to process documents in parallel if the output directory is the same. If you try to do so, sequential execution (in arbitrary order) of the lilypond-book processes is enforced instead by using a lock file.

In other words, to process documents foo.lytex and bar.lytex at the same time (via the make utility, for example), put them either into two different directories, say, foo/foo.lytex and bar/bar.lytex, or use command-line option --output with different values.

Note that LilyPond itself can process multiple input files in parallel, actually. Since lilypond-book passes a list of all snippets in a document to lilypond in one rush, parallel execution is possible by using its -djob-count option.

lilypond-book --process="lilypond -djob-count=4" \
              --output=foo \
              ... \
              foo.lytex