Fix quadratic command-line parsing #118
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There is only a single instance anyway.
Otherwise the config parser would run for every argument, resulting in quadratic parsing.
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Done, thanks. |
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This PR has also been opened on upstream ocamlformat: ocaml-ppx#2724
I rebased it to oxcaml in priority to pave the way for efficient automated testing (@ccasin).
Command‑line parsing occurs in two passes: one pass parses the actions, and a second pass parses the configuration.
Because the configuration parser is invoked for every input file, the overall parsing time grows quadratically with the number of files.
This patch memoizes the configuration so that the parser runs only once. The configuration changes are still applied to each input file, preserving the original ocamlformat behaviour while making the runtime independent of the number of inputs.
Below are two plots that illustrate the performance before and after the change. They show the time spent and the number of stat calls as functions of the number of input files, clearly demonstrating the quadratic behaviour that the patch removes.