Elixir compiler parallelisation attempt abandoned after race conditions and no gains

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A developer attempted to speed up the Elixir compiler by running type inference and typespec translation concurrently, since the two steps appeared to have no data dependencies. Multiple implementation approaches were tried, including spawn_monitor, manual message passing, and ETS-based inter-process communication, each producing errors such as unexpected message formats, receive timeouts, or performance regressions. A fallback strategy that avoided polling eventually compiled successfully and passed all tests, but introduced a data race bug caused by destructive ETS reads conflicting between the parallel and fallback code paths. After fixing the race condition, benchmarks across five modules of varying complexity showed no measurable performance improvement, with differences falling within noise margins. The experiment was ultimately abandoned, with the conclusion that the overhead of coordination negated any theoretical gains from parallelising the two compilation steps.

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