ruby.git/benchmark/array_join_regression.yml, branch master The Ruby Programming Language Speed up Array#join with a memcpy fast path 2026-06-11T18:59:01+00:00 Yaroslav Markin yaroslav@markin.net 2026-06-07T16:12:50+00:00 35b7652058a15509864a42a99cabec0dc157a6e4 When every element is a String sharing one ASCII-compatible fast-path encoding (UTF-8/US-ASCII/ASCII-8BIT) and the separator is compatible, build the result with a single memcpy pass instead of appending element by element through rb_str_buf_append. Other cases fall back to the existing path. 
When every element is a String sharing one ASCII-compatible fast-path
encoding (UTF-8/US-ASCII/ASCII-8BIT) and the separator is compatible, build
the result with a single memcpy pass instead of appending element by element
through rb_str_buf_append. Other cases fall back to the existing path.