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Minor changes to improve compilation speed #137

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Minor changes to improve compilation speed #137

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Commits on Feb 25, 2024

  1. Partially document current MSRV

    @Aeledfyr
    Aeledfyr committed Feb 25, 2024
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  2. Remove unnecessary internal generic parameter

    @Aeledfyr
    Aeledfyr committed Feb 25, 2024
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  3. Optimize compilation time of parsing functions on Linux 

    Iterator combinators have a noticable compilation time overhead
because they must be monomorphized and end up passing more code
to LLVM.  This code does get optimized out, but that takes time
and slows down the overall build.
    @Aeledfyr
    Aeledfyr committed Feb 25, 2024
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  4. Prevent debug macro from generating format_args when not in use 

    I'm not sure how much of a compile time impact this makes, but this
prevents the compiler from having to generate formatting code when
the debug macro is not in use.
    @Aeledfyr
    Aeledfyr committed Feb 25, 2024
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  5. Use Vec instead of HashMap when counting physical cores 

    The current implementation uses a HashMap to deduplicate the output
from each core of the same cpu.  This commit instead collects the
output for each core in to a Vec, and then sorts it to deduplicate
physical CPUs.

This reduces the code size processed by LLVM by 15-20%, as counted
by `cargo llvm-lines --lib -p num_cpus` on both debug and release.

These implementations have different performance characteristics:
- the HashMap must hash each key, and SipHash is slow on small keys
- the number of cores will be small (<1024) so sorting the list
  should be very fast
- the list will likely already be sorted

I have not benchmarked this code, but it should be around the same
speed or slightly faster (from testing against randomized lists).
    @Aeledfyr
    Aeledfyr committed Feb 25, 2024
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