An unrolled loop is created by sequentially listing the contents of a loop as code. In traditional compiled and interpreted languages, this can offer some speedups, for example because comparisons do not need to be executed every iteration of the loop. Here I've written a small benchmark to test how much of a speedup is gained in Scratch. The project runs a traditional repeat() 128x loop, and a 128x unrolled loop, which do nothing more than add pi (3.1415926...) to a variable. The results suggest quite strongly that unrolling a loop can deliver quite a large performance improvement. In Scratch, I see a speedup of about 150% Phosphorus and Sulfurous show speedups of 300-400%! This means that definite speedups can be achieved when programming projects that require loops where the number of repeats is known beforehand (e.g. fractals!) It also seems like a reasonable feature to add to sulfurous or phosphorus -- repeat() loops could be unrolled during compile time if the number of repeats is known.
