Commit f7360b88 authored by Hans-Peter Deifel's avatar Hans-Peter Deifel 🐢
Browse files

wta: Swap algorithm if transition count is too large 

The existing algorithm for generating unique transitions is inefficient if the
transition count is close to the maximal number of transitions. This now
switches to a different algorithm if the transition count is above 70% of the
maximum.
parent 44999948

src/random-wta/Generator.hs

+17 −1
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ import Control.Arrow ( (&&&) ) 
import qualified Data.Map.Strict            as M

import qualified Data.Set                   as S

import           Data.Coerce

import           Data.Ratio



import           Types                   hiding ( spec )

import           Probability
@@ -98,13 +99,28 @@ genTransitions = do 


-- TODO Implement (Random IndexedTransition)

uniqueTransitions :: Int -> IndexedTransition -> IO [IndexedTransition]

uniqueTransitions num (IndexedTransition.Index max) = helper S.empty num

uniqueTransitions num idxMax@(IndexedTransition.Index max)

  | fromIntegral num < fromIntegral max * (7%10) = uniqueTransitionsByGeneration num idxMax

  | otherwise       = uniqueTransitionsByElimination num idxMax



uniqueTransitionsByGeneration :: Int -> IndexedTransition -> IO [IndexedTransition]

uniqueTransitionsByGeneration num (IndexedTransition.Index max) = helper S.empty num

  where

    helper m 0 = return $ coerce (S.toList m)

    helper m c = do

      x <- randomRIO (0, max-1)

      if x `S.member` m then helper m c else helper (S.insert x m) (c-1)



uniqueTransitionsByElimination :: Int -> IndexedTransition -> IO [IndexedTransition]

uniqueTransitionsByElimination num (IndexedTransition.Index max) = helper whole num

  where

    helper free 0 = return $ coerce (S.toList (S.difference whole free))

    helper free c = do

      idx <- randomRIO (0, S.size free - 1)

      let x = S.elemAt idx free

      helper (S.delete x free) (c-1)



    whole = S.fromList [0..max-1]



genTransitions' :: Int -> Generator m (Vector (Vector (Transition m)))

genTransitions' numTransitions = do