DefMemo
A memoization macro (defmemo) for Elixir.
Adapted from : (Gustavo Brunoro) https://gist.github.com/brunoro/6159378
I found Gustavo's Gist when looking at memoization and elixir and fixed it to work with version 1.0.x. Since then I've fixed a few of the problems with the original implementation:
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will correctly memoize the results of functions with identical signatures but in different modules.
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will work with 'when' guard clauses in function definitions. (That was fun!)
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Added lots of lovely tests.
Usage
Add defmemo to your mix.exs file:
{:defmemo, "~> 0.1.0"}
And run:
mix deps.get
Before using a defmemo'd function (it's fine to define them), start_link must be called. e.g.
DefMemo.start_link
or you can add :defmemo into the applications section of your mix.exs:
[applications: [:logger, :defmemo]]
Example
defmodule FibMemo do
import DefMemo
defmemo fibs(0), do: 0
defmemo fibs(1), do: 1
defmemo fibs(n), do: fibs(n - 1) + fibs(n - 2)
def fib_10 do
fibs(10)
end
end
Performance
As you would expect for something like fibs, memoization provides dramatic performance improvements:
UNMEMOIZED VS MEMOIZED
***********************
fib (unmemoized)
function -> {result, running time(μs)}
==================================
fibs(30) -> {832040, 31089}
fibs(30) -> {832040, 31833}
FibMemo (memoized)
==================================
fibs(30) -> {832040, 79}
fibs(30) -> {832040, 3}
fibs(50) -> {12586269025, 103}
fibs(50) -> {12586269025, 3}
Note that these have also improved from version 0.1 to 0.1.1. The above numbers are on the low end of the spectrum with access ranging from 2 to 15 μs for me.
TODO
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Add test for supervisor crashing.
-
Look at injecting the type of result table used.
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Better documentation.
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More tests (alwaaaays with the testing!)
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Test with some biger data (e.g. for something like web crawling)
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~~Supervisor ~~
-
Redis Based ResultTable - I've been playing with this - obviously there are limitations on type and it's slower than gen server but there are of course circumstances where it could be useful but for the most part its not a good "fit".