The execution speed of a program produced by the Mozart compiler (version 1.4.0 implementing Oz 3) is very slow. On a 2012 set of [[The Computer Language Benchmarks Game|set of benchmarks]] it averagesaveraged about 50 times slower than that of the [[GNU Compiler Collection]] (GCC) for the C language, solving the benchmarks-tasks.{{when|date=September 2017}}<ref>[https://archive.today/20120713231944/http://shootout.alioth.debian.org/u32/which-programming-languages-are-fastest.php?calc=chart&gcc=on&oz=on The Computer Language Benchmarks Game]</ref>{{failed verification|date=February 2014}}
