What's the main reason ripgrep is fast?

According to the README, ripgrep's speed comes from multiple architectural choices [README.md:L183-L210]:

1. Rust's regex engine — Built on finite automata, SIMD, and aggressive literal optimizations for very fast searching. PCRE2 support is optional via the -P/--pcre2 flag.

2. UTF-8 decoding integration — Rust's regex library maintains performance while supporting full Unicode by building UTF-8 decoding directly into its deterministic finite automaton engine.

3. Smart search strategy selection — It supports both memory-mapped searching (better for single files) and incremental searching with an intermediate buffer (better for large directories), and automatically chooses the best approach.

4. Efficient ignore pattern matching — Uses a RegexSet to match a single file path against multiple glob patterns simultaneously, rather than sequentially.

5. Parallel directory traversal — Uses a lock-free parallel recursive directory iterator via crossbeam and ignore crates.

The README also notes that benchmarks on the Linux kernel show ripgrep completing searches in roughly 1/3 the time of git grep and 1/2 the time of hypergrep [README.md:L183-L210].