What's the main reason ripgrep is fast?

According to the README, ripgrep is fast for several key reasons:

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 [README.md:L183-L210].

2. Unicode support without performance loss: Rust's regex library maintains performance with full Unicode support by building UTF-8 decoding directly into its deterministic finite automaton engine [README.md:L183-L210].

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 [README.md:L183-L210].

4. Efficient ignore pattern matching: It applies .gitignore patterns using a RegexSet, meaning a single file path can be matched against multiple glob patterns simultaneously [README.md:L183-L210].

5. Parallel processing: It uses a lock-free parallel recursive directory iterator via crossbeam and ignore libraries [README.md:L183-L210].

The combination of these factors—particularly the underlying regex engine and intelligent search strategy selection—makes ripgrep significantly faster than competing tools like The Silver Searcher, ack, and git grep.

FOLLOW_UPS:

• How does ripgrep choose between memory map and buffer search?
• What is the difference between ripgrep's default regex engine and PCRE2?
• How does the DFA size limit affect search performance?