What's the main reason ripgrep is fast?

According to the README, ripgrep is fast for several key reasons [README.md:L183-L210]:

1. Rust's regex engine – It's built on top of Rust's regex engine, which uses finite automata, SIMD, and aggressive literal optimizations to make searching very fast. (PCRE2 support can be opted into with the -P/--pcre2 flag.)

2. Unicode support with performance – Rust's regex library maintains performance with full Unicode support by building UTF-8 decoding directly into its deterministic finite automaton engine.

3. Smart search strategy selection – It supports searching with either memory maps (better for single files) or incrementally with an intermediate buffer (better for large directories), and ripgrep automatically chooses the best strategy for you.

4. Efficient gitignore matching – It applies ignore patterns from .gitignore files using a RegexSet, allowing a single file path to be matched against multiple glob patterns simultaneously.

5. Parallel directory iteration – It uses a lock-free parallel recursive directory iterator via crossbeam and ignore libraries.

The README also notes that detailed benchmarks and analysis are available on the author's blog, and a single benchmark is never enough to fully evaluate performance claims.

FOLLOW_UPS:

• How does ripgrep handle binary files?
• What's the difference between memory map and buffer searching?
• Can you customize gitignore pattern matching behavior?