Log-space computable function

In computational complexity theory, a log-space computable function is a function $$f\colon \Sigma^\ast \rightarrow \Sigma^\ast$$ that requires only $$O(\log n)$$ memory to be computed (this restriction does not apply to the size of the output). The computation is generally done by means of a log-space transducer.

Log-space reductions
The main use for log-space computable functions is in log-space reductions. This is a means of transforming an instance of one problem into an instance of another problem, using only logarithmic space.

Examples of log-space computable functions

 * Function converting a problem of a non-deterministic Turing machine that decides a language A in log-space to ST-connectivity.