Mercurial > octave
view scripts/miscellaneous/memoize.m @ 31247:3dae836c598c
doc: Expand and edit documentation for memoization (bug #60860)
author | Arun Giridhar <arungiridhar@gmail.com> |
---|---|
date | Fri, 30 Sep 2022 06:38:59 -0400 |
parents | a887ffb997a7 |
children | a40c0b7aa376 |
line wrap: on
line source
######################################################################## ## ## Copyright (C) 2021 The Octave Project Developers ## ## See the file COPYRIGHT.md in the top-level directory of this ## distribution or <https://octave.org/copyright/>. ## ## This file is part of Octave. ## ## Octave is free software: you can redistribute it and/or modify it ## under the terms of the GNU General Public License as published by ## the Free Software Foundation, either version 3 of the License, or ## (at your option) any later version. ## ## Octave is distributed in the hope that it will be useful, but ## WITHOUT ANY WARRANTY; without even the implied warranty of ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ## GNU General Public License for more details. ## ## You should have received a copy of the GNU General Public License ## along with Octave; see the file COPYING. If not, see ## <https://www.gnu.org/licenses/>. ## ######################################################################## ## -*- texinfo -*- ## @deftypefn {} {@var{mem_fcn_handle} =} memoize (@var{fcn_handle}) ## ## Create a memoized version @var{mem_fcn_handle} of function ## @var{fcn_handle}. ## ## Each call to the memoized version @var{mem_fcn_handle} checks the inputs ## against an internally maintained table, and if the inputs have occurred ## previously, then the result of the function call is returned from the table ## itself instead of evaluating the full function again. This speeds up the ## execution of functions that are called with the same inputs multiple times. ## ## For example, here we take a slow user-written function named ## @code{slow_fcn} and memoize it to a new handle @code{cyc}. ## The first executions of both versions take the same time, but the subsequent ## executions of the memoized version returns the previously computed value, ## thus reducing 2.4 seconds of runtime to only 2.4 milliseconds. The final ## check verifies that the same result was returned from both versions. ## ## @example ## @group ## >> tic; @var{p} = slow_fcn (5040); toc ## Elapsed time is 2.41244 seconds. ## >> tic; @var{p} = slow_fcn (5040); toc ## Elapsed time is 2.41542 seconds. ## ## >> cyc = memoize (@@slow_fcn); ## >> tic; @var{r} = cyc (5040); toc ## Elapsed time is 2.42609 seconds. ## >> tic; @var{r} = cyc (5040); toc ## Elapsed time is 0.00236511 seconds. ## ## >> all (@var{p} == @var{r}) ## ans = 1 ## @end group ## @end example ## ## @seealso{clearAllMemoizedCaches} ## @end deftypefn function mem_fcn_handle = memoize (fcn_handle) if (nargin != 1 || nargout > 1) print_usage (); endif if (! isa (fcn_handle, "function_handle")) error ("memoize: FCN_HANDLE must be a function handle"); endif mem_fcn_handle = __memoize__ (fcn_handle); endfunction %!test %! fcn1 = memoize (@sin); %! assert (isa (fcn1, "matlab.lang.MemoizedFunction")); %! fcn1 (pi); %! fcn2 = memoize (@sin); %! fcn2 (2*pi); %! assert (isequal (fcn1, fcn2)) %!test %! fcn = memoize (@rand); %! a = fcn (); %! b = fcn (); %! assert (a, b); %! fcn2 = memoize (@rand); %! c = fcn2 (); %! assert (a, c); %!test %! fcn = memoize (@plus); %! fcn.stats; %! stats (fcn); %! clearCache (fcn); %! fcn.clearCache; # Test input validation %!error memoize (); %!error memoize (1, 2); %!error [a, b] = memoize (1); %!error memoize (1);