Bignum math isn't optimized for performance yet. See this discussion: http://www.reddit.com/r/rust/comments/1xcq1q/c_gcc_vs_rust_wtf/ http://www.reddit.com/r/r

Bignum math isn't optimized for performance yet. See this discussion: http://www.reddit.com/r/rust/comments/1xcq1q/c_gcc_vs_rust_wtf/ http://www.reddit.com/r/rust/comments/1xcq1q/c_gcc_vs_rust_w... There are also already some patches making rust a lot less worse: https://github.com/mozilla/rust/pull/12209 https://github.com/mozilla/rust/pull/12209