-- Hoogle documentation, generated by Haddock
-- See Hoogle, http://www.haskell.org/hoogle/


-- | HMEP Multi Expression Programming –
--   a genetic programming variant
--   
--   A multi expression programming implementation with focus on speed.
--   
--   <a>https://en.wikipedia.org/wiki/Multi_expression_programming</a>
@package hmep
@version 0.1.0


-- | <h1>Core MEP data structures</h1>
module AI.MEP.Types

-- | A chromosome is a vector of genes
type Chromosome a = Vector (Gene a Int)

-- | Either a terminal symbol or a three-address code (a function and two
--   pointers)
data Gene a i
[C] :: a -> Gene a i
[Var] :: Int -> Gene a i
[Op] :: F a -> i -> i -> Gene a i

-- | A function and its symbolic representation
type F a = (Char, a -> a -> a)

-- | List of chromosomes
type Population a = [Chromosome a]

-- | Evaluated population
type Generation a = [Phenotype a]

-- | Loss value, chromosome, and the best expression indices vector
type Phenotype a = (Double, Chromosome a, Vector Int)
instance (GHC.Show.Show a, GHC.Show.Show i) => GHC.Show.Show (AI.MEP.Types.Gene a i)

module AI.MEP.Run

-- | Evaluate each subexpression in a chromosome
evaluate :: Num a => Chromosome a -> Vector a -> Vector a

-- | Generate code for the functions with a single output
generateCode :: Phenotype Double -> String

-- | Average population loss
avgLoss :: Generation Double -> Double


-- | Copyright Bogdan Penkovsky (c) 2017
--   
--   <h1>Multiple Expression Programming</h1>
--   
--   <h2>Example application: trigonometry cheating</h2>
--   
--   Suppose, you forgot certain trigonometric identities. For instance,
--   you want to express cos^2(x) using sin(x). No problem, set the target
--   function cos^2(x) in the dataset and add sin to the arithmetic set of
--   operators <tt>{+,-,*,/}</tt>. See app/Main.hs.
--   
--   After running
--   
--   <pre>
--   $ stack build &amp;&amp; stack exec hmep-demo
--   
--   </pre>
--   
--   We obtain
--   
--   <pre>
--   Average loss in the initial population 15.268705681244962
--   Population 10: average loss 14.709728527360586
--   Population 20: average loss 13.497114190675477
--   Population 30: average loss 8.953185872653737
--   Population 40: average loss 8.953185872653737
--   Population 50: average loss 3.3219954564955856e-15
--   
--   </pre>
--   
--   The average value of 3.3e-15 is close to zero, indicating that the
--   exact expression was found!
--   
--   The produced output was:
--   
--   <pre>
--   Interpreted expression:
--   v1 = sin x0
--   v2 = v1 * v1
--   result = 1 - v2
--   
--   </pre>
--   
--   From here we can infer that <tt> cos^2(x) = 1 - v2 = 1 - v1 * v1 = 1 -
--   sin^2(x). </tt>
--   
--   Sweet!
module AI.MEP

-- | A chromosome is a vector of genes
type Chromosome a = Vector (Gene a Int)

-- | Either a terminal symbol or a three-address code (a function and two
--   pointers)
data Gene a i

-- | List of chromosomes
type Population a = [Chromosome a]

-- | Loss value, chromosome, and the best expression indices vector
type Phenotype a = (Double, Chromosome a, Vector Int)
data Config a
Config :: Double -> Double -> Double -> Double -> Int -> Int -> Int -> Vector (F a) -> Int -> Config a

-- | Probability of constant generation
[p'const] :: Config a -> Double

-- | Probability of variable generation. The probability of operator
--   generation is inferred automatically as <tt>1 - p'const - p'var</tt>.
[p'var] :: Config a -> Double

-- | Mutation probability
[p'mutation] :: Config a -> Double

-- | Crossover probability
[p'crossover] :: Config a -> Double

-- | The chromosome length
[c'length] :: Config a -> Int

-- | A (sub)population size
[c'popSize] :: Config a -> Int

-- | Number of subpopulations (1 or more) [not implemented]
[c'popN] :: Config a -> Int

-- | Functions pool with their symbolic representations
[c'ops] :: Config a -> Vector (F a)

-- | The input dimensionality
[c'vars] :: Config a -> Int

-- | <pre>
--   defaultConfig = Config
--     {
--       p'const = 0.1
--     , p'var = 0.4
--     , p'mutation = 0.1
--     , p'crossover = 0.9
--   
--     , c'length = 50
--     , c'popSize = 100
--     , c'popN = 1
--     , c'ops = V.empty  -- &lt;-- To be overridden
--     , c'vars = 1
--     }
--   </pre>
defaultConfig :: Config Double

-- | A function to minimize.
--   
--   The argument is a vector evaluation function whose input is a vector
--   (length <tt>c'vars</tt>) and ouput is a vector with a different length
--   <tt>c'length</tt>.
--   
--   The result is a vector of the best indices and a scalar loss value.
type LossFunction a = (Vector a -> Vector a) -> (Vector Int, Double)

-- | Randomly generate a new population
initialize :: PrimMonad m => Config Double -> RandT m (Population Double)
evaluateGeneration :: Num a => LossFunction a -> Population a -> Generation a

-- | Average population loss
avgLoss :: Generation Double -> Double

-- | Selection operator that produces the next evaluated population.
--   
--   Standard algorithm: the best offspring O replaces the worst individual
--   W in the current population if O is better than W.
evolve :: PrimMonad m => Config Double -> LossFunction Double -> (Chromosome Double -> RandT m (Chromosome Double)) -> (Chromosome Double -> Chromosome Double -> RandT m (Chromosome Double, Chromosome Double)) -> (Generation Double -> RandT m (Chromosome Double)) -> Generation Double -> RandT m (Generation Double)

-- | Binary tournament selection
binaryTournament :: (PrimMonad m, Ord a) => Generation a -> RandT m (Chromosome a)

-- | Uniform crossover operator
crossover :: PrimMonad m => Chromosome a -> Chromosome a -> RandT m (Chromosome a, Chromosome a)

-- | Mutation operator with up to three mutations per chromosome
mutation3 :: PrimMonad m => Config Double -> Chromosome Double -> RandT m (Chromosome Double)

-- | Mutation operator with a fixed mutation probability of each gene
smoothMutation :: PrimMonad m => Double -> Config Double -> Chromosome Double -> RandT m (Chromosome Double)

-- | Randomly initialize a new chromosome. By definition, the first gene is
--   terminal (a constant or a variable).
newChromosome :: PrimMonad m => Config Double -> RandT m (Chromosome Double)

-- | Generate code for the functions with a single output
generateCode :: Phenotype Double -> String

-- | <a>RandT</a> type, equivalent to a <tt>ReaderT</tt> (<a>Gen</a>
--   (<a>PrimState</a> m))
--   
--   This lets you build simple or complex random generation routines
--   without having the generator passed all around and just run the whole
--   thing in the end, most likely by using <a>mwc</a>.
data RandT (m :: * -> *) a :: (* -> *) -> * -> *
runRandIO :: RandT IO a -> IO a