An exercise on polyglossy: the same problem solved on multiple languages
Optimized the Elixir implementation to cache the values of `sum n`.
Currently the values are cached in a per-process-basis. The implementation could be further optimized if we were able to cache the values globally. This could be accoplished via message passing, sending requests to the `main` process and collecting the responses.
1 file changed, 40 insertions, 17 deletions
| Status | File Name | N° Changes | Insertions | Deletions |
| Modified | Elixir/digital_sum.ex | 57 | 40 | 17 |
diff --git a/Elixir/digital_sum.ex b/Elixir/digital_sum.ex @@ -34,33 +34,47 @@ defmodule Conjecture do def get_counterexpl start, max, n_processes do receive do parent_pid -> - if counterexpl start, max, n_processes do - send parent_pid, :fail - else - send parent_pid, :ok + case counterexpl start, max, n_processes, %{} do + :found -> send parent_pid, :fail + _ -> send parent_pid, :ok end end end - def counterexpl a, max, n_processes do - cond do - iter a, 0 -> true - a + n_processes <= max -> - counterexpl (a + n_processes), max, n_processes - true -> false + def counterexpl a, max, n_processes, sums_cache do + case iter a, 0, sums_cache do + :found -> :found + sums_cache_updated -> + if a + n_processes <= max do + counterexpl (a + n_processes), max, n_processes, sums_cache_updated + else + sums_cache_updated + end end end - def iter a, b do - cond do - test a, b -> true - b + 1 < a -> iter a, b + 1 - true -> false + def iter a, b, sums_cache do + case test a, b, sums_cache do + :found -> :found + sums_cache_updated -> + if b + 1 < a do + iter a, b + 1, sums_cache_updated + else + sums_cache_updated + end end end - def test a, b do - 0 != rem(sum(a + b) - sum(a) - sum(b), 9) + def test a, b, sums_cache do + {sums_cache_a, sum_a} = lookup sums_cache, a + {sums_cache_b, sum_b} = lookup sums_cache_a, b + {sums_cache_a_b, sum_a_b} = lookup sums_cache_b, a + b + + if 0 != rem(sum_a_b - sum_a - sum_b, 9) do + :found + else + sums_cache_a_b + end end def sum 0 do 0 end @@ -71,4 +85,13 @@ defmodule Conjecture do d + sum r end + + def lookup map, n do + if Map.has_key? map, n do + {map, map[n]} + else + sum_n = sum n + {Map.put(map, n, sum_n), sum_n} + end + end end