As someone who's programmed extensively in both C and OCaml, I wish my functional programs could approach the performance of my C programs. Although I doubt co

As someone who's programmed extensively in both C and OCaml, I wish my functional programs could approach the performance of my C programs. Although I doubt code locality differs much between the two (although FP might fare worse due to the code space overhead imposed by polymorphism), data locality is generally much worse in FP languages due to poorer control over data layout. (Garbage collection, run-time type tagging, excessive indirection, and inability to specify structure layout all contribute to this.) The purported benefits of FP performance generally stem from either (a) the ability to ignore pointer aliasing effects when optimizing, which is not unique to FP (see Fortran, or C's restrict keyword), (b) the ability to automatically parallelize code due to immutability of data, which is generally far less a benefit than it sounds, or (c) the ability for the compiler or runtime to optimize away computations which are never used, which, while easier with a pure FP language, is again not unique to FP (see most modern C compilers).