Copyright | (c) Edward Kmett 2013-2015 |
---|---|
License | BSD3 |
Maintainer | Edward Kmett <ekmett@gmail.com> |
Stability | experimental |
Portability | non-portable |
Safe Haskell | Trustworthy |
Language | Haskell98 |
Numeric.Log
Description
Documentation
Log
-domain Float
and Double
values.
Instances
Monad Log Source # | |
Functor Log Source # | |
Applicative Log Source # | |
Foldable Log Source # | |
Defined in Numeric.Log Methods fold :: Monoid m => Log m -> m # foldMap :: Monoid m => (a -> m) -> Log a -> m # foldr :: (a -> b -> b) -> b -> Log a -> b # foldr' :: (a -> b -> b) -> b -> Log a -> b # foldl :: (b -> a -> b) -> b -> Log a -> b # foldl' :: (b -> a -> b) -> b -> Log a -> b # foldr1 :: (a -> a -> a) -> Log a -> a # foldl1 :: (a -> a -> a) -> Log a -> a # elem :: Eq a => a -> Log a -> Bool # maximum :: Ord a => Log a -> a # | |
Traversable Log Source # | |
Serial1 Log Source # | |
Defined in Numeric.Log Methods serializeWith :: MonadPut m => (a -> m ()) -> Log a -> m () # deserializeWith :: MonadGet m => m a -> m (Log a) # | |
Comonad Log Source # | |
ComonadApply Log Source # | |
Distributive Log Source # | |
Hashable1 Log Source # | |
Defined in Numeric.Log | |
Traversable1 Log Source # | |
Foldable1 Log Source # | |
Apply Log Source # | |
Bind Log Source # | |
Extend Log Source # | |
(RealFloat a, Unbox a) => Vector Vector (Log a) Source # | |
Defined in Numeric.Log Methods basicUnsafeFreeze :: PrimMonad m => Mutable Vector (PrimState m) (Log a) -> m (Vector (Log a)) # basicUnsafeThaw :: PrimMonad m => Vector (Log a) -> m (Mutable Vector (PrimState m) (Log a)) # basicLength :: Vector (Log a) -> Int # basicUnsafeSlice :: Int -> Int -> Vector (Log a) -> Vector (Log a) # basicUnsafeIndexM :: Monad m => Vector (Log a) -> Int -> m (Log a) # basicUnsafeCopy :: PrimMonad m => Mutable Vector (PrimState m) (Log a) -> Vector (Log a) -> m () # | |
Unbox a => MVector MVector (Log a) Source # | |
Defined in Numeric.Log Methods basicLength :: MVector s (Log a) -> Int # basicUnsafeSlice :: Int -> Int -> MVector s (Log a) -> MVector s (Log a) # basicOverlaps :: MVector s (Log a) -> MVector s (Log a) -> Bool # basicUnsafeNew :: PrimMonad m => Int -> m (MVector (PrimState m) (Log a)) # basicInitialize :: PrimMonad m => MVector (PrimState m) (Log a) -> m () # basicUnsafeReplicate :: PrimMonad m => Int -> Log a -> m (MVector (PrimState m) (Log a)) # basicUnsafeRead :: PrimMonad m => MVector (PrimState m) (Log a) -> Int -> m (Log a) # basicUnsafeWrite :: PrimMonad m => MVector (PrimState m) (Log a) -> Int -> Log a -> m () # basicClear :: PrimMonad m => MVector (PrimState m) (Log a) -> m () # basicSet :: PrimMonad m => MVector (PrimState m) (Log a) -> Log a -> m () # basicUnsafeCopy :: PrimMonad m => MVector (PrimState m) (Log a) -> MVector (PrimState m) (Log a) -> m () # basicUnsafeMove :: PrimMonad m => MVector (PrimState m) (Log a) -> MVector (PrimState m) (Log a) -> m () # basicUnsafeGrow :: PrimMonad m => MVector (PrimState m) (Log a) -> Int -> m (MVector (PrimState m) (Log a)) # | |
(RealFloat a, Precise a, Enum a) => Enum (Log a) Source # | |
Eq a => Eq (Log a) Source # | |
(RealFloat a, Precise a) => Floating (Log a) Source # | |
(Precise a, RealFloat a) => Fractional (Log a) Source # | |
Data a => Data (Log a) Source # | |
Defined in Numeric.Log Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Log a -> c (Log a) # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Log a) # dataTypeOf :: Log a -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Log a)) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Log a)) # gmapT :: (forall b. Data b => b -> b) -> Log a -> Log a # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Log a -> r # gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Log a -> r # gmapQ :: (forall d. Data d => d -> u) -> Log a -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> Log a -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> Log a -> m (Log a) # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Log a -> m (Log a) # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Log a -> m (Log a) # | |
(Precise a, RealFloat a) => Num (Log a) Source # | |
Ord a => Ord (Log a) Source # | |
(Floating a, Read a) => Read (Log a) Source # | |
(Precise a, RealFloat a, Ord a) => Real (Log a) Source # | |
Defined in Numeric.Log Methods toRational :: Log a -> Rational # | |
(Precise a, RealFloat a) => RealFrac (Log a) Source # | |
(Floating a, Show a) => Show (Log a) Source # | |
Generic (Log a) Source # | |
(Precise a, RealFloat a) => Semigroup (Log a) Source # | |
(Precise a, RealFloat a) => Monoid (Log a) Source # | |
Storable a => Storable (Log a) Source # | |
Binary a => Binary (Log a) Source # | |
Serial a => Serial (Log a) Source # | |
Defined in Numeric.Log | |
Serialize a => Serialize (Log a) Source # | |
NFData a => NFData (Log a) Source # | |
Defined in Numeric.Log | |
Hashable a => Hashable (Log a) Source # | |
Defined in Numeric.Log | |
(RealFloat a, Unbox a) => Unbox (Log a) Source # | |
Defined in Numeric.Log | |
data MVector s (Log a) Source # | |
Defined in Numeric.Log | |
type Rep (Log a) Source # | |
Defined in Numeric.Log | |
data Vector (Log a) Source # | |
Defined in Numeric.Log |
class Floating a => Precise a where Source #
This provides log1p
and expm1
for working more accurately with small numbers.
Methods
Computes log(1 + x)
This is far enough from 0 that the Taylor series is defined.
This can provide much more accurate answers for logarithms of numbers close to 1 (x near 0).
These arise when working wth log-scale probabilities a lot.
The Taylor series for exp(x) is given by
exp(x) = 1 + x + x^2/2! + ...
When x
is small, the leading 1 consumes all of the available precision.
This computes:
exp(x) - 1 = x + x^2/2! + ..
which can afford you a great deal of additional precision if you move things around algebraically to provide the 1 by other means.
sum :: (RealFloat a, Precise a, Foldable f) => f (Log a) -> Log a Source #
Efficiently and accurately compute the sum of a set of log-domain numbers
While folding with (+)
accomplishes the same end, it requires an
additional n-2
logarithms to sum n
terms. In addition,
here we introduce fewer opportunities for round-off error.
While for small quantities the naive sum accumulates error,
>>>
let xs = Prelude.replicate 40000 (Exp 1e-4) :: [Log Float]
>>>
Prelude.sum xs ~= 4.00e4
True
This sum gives a more accurate result,
>>>
Numeric.Log.sum xs ~= 4.00e4
True
NB: This does require two passes over the data.