Copyright | (c) Edward Kmett 2010-2015 |
---|---|
License | BSD3 |
Maintainer | ekmett@gmail.com |
Stability | experimental |
Portability | GHC only |
Safe Haskell | None |
Language | Haskell2010 |
- AD modes
- Gradients (Reverse Mode)
- Higher Order Gradients (Sparse-on-Reverse)
- Variadic Gradients (Sparse or Kahn)
- Jacobians (Sparse or Reverse)
- Higher Order Jacobian (Sparse-on-Reverse)
- Transposed Jacobians (Forward Mode)
- Hessian (Sparse-On-Reverse)
- Hessian Tensors (Sparse or Sparse-On-Reverse)
- Hessian Tensors (Sparse)
- Hessian Vector Products (Forward-On-Reverse)
- Derivatives (Forward Mode)
- Derivatives (Tower)
- Directional Derivatives (Forward Mode)
- Directional Derivatives (Tower)
- Taylor Series (Tower)
- Maclaurin Series (Tower)
- Gradient Descent
Mixed-Mode Automatic Differentiation.
Each combinator exported from this module chooses an appropriate AD mode. The following basic operations are supported, modified as appropriate by the suffixes below:
grad
computes the gradient (partial derivatives) of a function at a pointjacobian
computes the Jacobian matrix of a function at a pointdiff
computes the derivative of a function at a pointdu
computes a directional derivative of a function at a pointhessian
compute the Hessian matrix (matrix of second partial derivatives) of a function at a point
The suffixes have the following meanings:
'
-- also return the answerWith
lets the user supply a function to blend the input with the outputF
is a version of the base function lifted to return aTraversable
(orFunctor
) results
means the function returns all higher derivatives in a list or f-branchingStream
T
means the result is transposed with respect to the traditional formulation.0
means that the resulting derivative list is padded with 0s at the end.
Synopsis
- data AD s a
- class (Num t, Num (Scalar t)) => Mode t where
- type family Scalar t
- grad :: (Traversable f, Num a) => (forall s. Reifies s Tape => f (Reverse s a) -> Reverse s a) -> f a -> f a
- grad' :: (Traversable f, Num a) => (forall s. Reifies s Tape => f (Reverse s a) -> Reverse s a) -> f a -> (a, f a)
- gradWith :: (Traversable f, Num a) => (a -> a -> b) -> (forall s. Reifies s Tape => f (Reverse s a) -> Reverse s a) -> f a -> f b
- gradWith' :: (Traversable f, Num a) => (a -> a -> b) -> (forall s. Reifies s Tape => f (Reverse s a) -> Reverse s a) -> f a -> (a, f b)
- grads :: (Traversable f, Num a) => (forall s. f (AD s (Sparse a)) -> AD s (Sparse a)) -> f a -> Cofree f a
- class Num a => Grad i o o' a | i -> a o o', o -> a i o', o' -> a i o
- vgrad :: Grad i o o' a => i -> o
- vgrad' :: Grad i o o' a => i -> o'
- class Num a => Grads i o a | i -> a o, o -> a i
- vgrads :: Grads i o a => i -> o
- jacobian :: (Traversable f, Functor g, Num a) => (forall s. Reifies s Tape => f (Reverse s a) -> g (Reverse s a)) -> f a -> g (f a)
- jacobian' :: (Traversable f, Functor g, Num a) => (forall s. Reifies s Tape => f (Reverse s a) -> g (Reverse s a)) -> f a -> g (a, f a)
- jacobianWith :: (Traversable f, Functor g, Num a) => (a -> a -> b) -> (forall s. Reifies s Tape => f (Reverse s a) -> g (Reverse s a)) -> f a -> g (f b)
- jacobianWith' :: (Traversable f, Functor g, Num a) => (a -> a -> b) -> (forall s. Reifies s Tape => f (Reverse s a) -> g (Reverse s a)) -> f a -> g (a, f b)
- jacobians :: (Traversable f, Functor g, Num a) => (forall s. f (AD s (Sparse a)) -> g (AD s (Sparse a))) -> f a -> g (Cofree f a)
- jacobianT :: (Traversable f, Functor g, Num a) => (forall s. f (AD s (Forward a)) -> g (AD s (Forward a))) -> f a -> f (g a)
- jacobianWithT :: (Traversable f, Functor g, Num a) => (a -> a -> b) -> (forall s. f (AD s (Forward a)) -> g (AD s (Forward a))) -> f a -> f (g b)
- hessian :: (Traversable f, Num a) => (forall s. Reifies s Tape => f (On (Reverse s (Sparse a))) -> On (Reverse s (Sparse a))) -> f a -> f (f a)
- hessian' :: (Traversable f, Num a) => (forall s. f (AD s (Sparse a)) -> AD s (Sparse a)) -> f a -> (a, f (a, f a))
- hessianF :: (Traversable f, Functor g, Num a) => (forall s. Reifies s Tape => f (On (Reverse s (Sparse a))) -> g (On (Reverse s (Sparse a)))) -> f a -> g (f (f a))
- hessianF' :: (Traversable f, Functor g, Num a) => (forall s. f (AD s (Sparse a)) -> g (AD s (Sparse a))) -> f a -> g (a, f (a, f a))
- hessianProduct :: (Traversable f, Num a) => (forall s. Reifies s Tape => f (On (Reverse s (Forward a))) -> On (Reverse s (Forward a))) -> f (a, a) -> f a
- hessianProduct' :: (Traversable f, Num a) => (forall s. Reifies s Tape => f (On (Reverse s (Forward a))) -> On (Reverse s (Forward a))) -> f (a, a) -> f (a, a)
- diff :: Num a => (forall s. AD s (Forward a) -> AD s (Forward a)) -> a -> a
- diffF :: (Functor f, Num a) => (forall s. AD s (Forward a) -> f (AD s (Forward a))) -> a -> f a
- diff' :: Num a => (forall s. AD s (Forward a) -> AD s (Forward a)) -> a -> (a, a)
- diffF' :: (Functor f, Num a) => (forall s. AD s (Forward a) -> f (AD s (Forward a))) -> a -> f (a, a)
- diffs :: Num a => (forall s. AD s (Tower a) -> AD s (Tower a)) -> a -> [a]
- diffsF :: (Functor f, Num a) => (forall s. AD s (Tower a) -> f (AD s (Tower a))) -> a -> f [a]
- diffs0 :: Num a => (forall s. AD s (Tower a) -> AD s (Tower a)) -> a -> [a]
- diffs0F :: (Functor f, Num a) => (forall s. AD s (Tower a) -> f (AD s (Tower a))) -> a -> f [a]
- du :: (Functor f, Num a) => (forall s. f (AD s (Forward a)) -> AD s (Forward a)) -> f (a, a) -> a
- du' :: (Functor f, Num a) => (forall s. f (AD s (Forward a)) -> AD s (Forward a)) -> f (a, a) -> (a, a)
- duF :: (Functor f, Functor g, Num a) => (forall s. f (AD s (Forward a)) -> g (AD s (Forward a))) -> f (a, a) -> g a
- duF' :: (Functor f, Functor g, Num a) => (forall s. f (AD s (Forward a)) -> g (AD s (Forward a))) -> f (a, a) -> g (a, a)
- dus :: (Functor f, Num a) => (forall s. f (AD s (Tower a)) -> AD s (Tower a)) -> f [a] -> [a]
- dus0 :: (Functor f, Num a) => (forall s. f (AD s (Tower a)) -> AD s (Tower a)) -> f [a] -> [a]
- dusF :: (Functor f, Functor g, Num a) => (forall s. f (AD s (Tower a)) -> g (AD s (Tower a))) -> f [a] -> g [a]
- dus0F :: (Functor f, Functor g, Num a) => (forall s. f (AD s (Tower a)) -> g (AD s (Tower a))) -> f [a] -> g [a]
- taylor :: Fractional a => (forall s. AD s (Tower a) -> AD s (Tower a)) -> a -> a -> [a]
- taylor0 :: Fractional a => (forall s. AD s (Tower a) -> AD s (Tower a)) -> a -> a -> [a]
- maclaurin :: Fractional a => (forall s. AD s (Tower a) -> AD s (Tower a)) -> a -> [a]
- maclaurin0 :: Fractional a => (forall s. AD s (Tower a) -> AD s (Tower a)) -> a -> [a]
- gradientDescent :: (Traversable f, Fractional a, Ord a) => (forall s. Reifies s Tape => f (Reverse s a) -> Reverse s a) -> f a -> [f a]
- gradientAscent :: (Traversable f, Fractional a, Ord a) => (forall s. Reifies s Tape => f (Reverse s a) -> Reverse s a) -> f a -> [f a]
- conjugateGradientDescent :: (Traversable f, Ord a, Fractional a) => (forall s. Chosen s => f (Or s (On (Forward (Forward a))) (Kahn a)) -> Or s (On (Forward (Forward a))) (Kahn a)) -> f a -> [f a]
- conjugateGradientAscent :: (Traversable f, Ord a, Fractional a) => (forall s. Chosen s => f (Or s (On (Forward (Forward a))) (Kahn a)) -> Or s (On (Forward (Forward a))) (Kahn a)) -> f a -> [f a]
- stochasticGradientDescent :: (Traversable f, Fractional a, Ord a) => (forall s. Reifies s Tape => e -> f (Reverse s a) -> Reverse s a) -> [e] -> f a -> [f a]
Documentation
Instances
AD modes
class (Num t, Num (Scalar t)) => Mode t where Source #
Instances
Instances
Gradients (Reverse Mode)
grad :: (Traversable f, Num a) => (forall s. Reifies s Tape => f (Reverse s a) -> Reverse s a) -> f a -> f a Source #
The grad
function calculates the gradient of a non-scalar-to-scalar function with reverse-mode AD in a single pass.
>>>
grad (\[x,y,z] -> x*y+z) [1,2,3]
[2,1,1]
>>>
grad (\[x,y] -> x**y) [0,2]
[0.0,NaN]
grad' :: (Traversable f, Num a) => (forall s. Reifies s Tape => f (Reverse s a) -> Reverse s a) -> f a -> (a, f a) Source #
The grad'
function calculates the result and gradient of a non-scalar-to-scalar function with reverse-mode AD in a single pass.
>>>
grad' (\[x,y,z] -> x*y+z) [1,2,3]
(5,[2,1,1])
gradWith :: (Traversable f, Num a) => (a -> a -> b) -> (forall s. Reifies s Tape => f (Reverse s a) -> Reverse s a) -> f a -> f b Source #
gradWith' :: (Traversable f, Num a) => (a -> a -> b) -> (forall s. Reifies s Tape => f (Reverse s a) -> Reverse s a) -> f a -> (a, f b) Source #
Higher Order Gradients (Sparse-on-Reverse)
grads :: (Traversable f, Num a) => (forall s. f (AD s (Sparse a)) -> AD s (Sparse a)) -> f a -> Cofree f a Source #
Variadic Gradients (Sparse or Kahn)
Variadic combinators for variadic mixed-mode automatic differentiation.
Unfortunately, variadicity comes at the expense of being able to use
quantification to avoid sensitivity confusion, so be careful when
counting the number of auto
calls you use when taking the gradient
of a function that takes gradients!
class Num a => Grad i o o' a | i -> a o o', o -> a i o', o' -> a i o Source #
Jacobians (Sparse or Reverse)
jacobian :: (Traversable f, Functor g, Num a) => (forall s. Reifies s Tape => f (Reverse s a) -> g (Reverse s a)) -> f a -> g (f a) Source #
The jacobian
function calculates the jacobian of a non-scalar-to-non-scalar function with reverse AD lazily in m
passes for m
outputs.
>>>
jacobian (\[x,y] -> [y,x,x*y]) [2,1]
[[0,1],[1,0],[1,2]]
jacobian' :: (Traversable f, Functor g, Num a) => (forall s. Reifies s Tape => f (Reverse s a) -> g (Reverse s a)) -> f a -> g (a, f a) Source #
The jacobian'
function calculates both the result and the Jacobian of a nonscalar-to-nonscalar function, using m
invocations of reverse AD,
where m
is the output dimensionality. Applying fmap snd
to the result will recover the result of jacobian
| An alias for gradF'
>>>
jacobian' (\[x,y] -> [y,x,x*y]) [2,1]
[(1,[0,1]),(2,[1,0]),(2,[1,2])]
jacobianWith :: (Traversable f, Functor g, Num a) => (a -> a -> b) -> (forall s. Reifies s Tape => f (Reverse s a) -> g (Reverse s a)) -> f a -> g (f b) Source #
'jacobianWith g f' calculates the Jacobian of a non-scalar-to-non-scalar function f
with reverse AD lazily in m
passes for m
outputs.
Instead of returning the Jacobian matrix, the elements of the matrix are combined with the input using the g
.
jacobian
==jacobianWith
(_ dx -> dx)jacobianWith
const
== (f x ->const
x<$>
f x)
jacobianWith' :: (Traversable f, Functor g, Num a) => (a -> a -> b) -> (forall s. Reifies s Tape => f (Reverse s a) -> g (Reverse s a)) -> f a -> g (a, f b) Source #
jacobianWith
g f' calculates both the result and the Jacobian of a nonscalar-to-nonscalar function f
, using m
invocations of reverse AD,
where m
is the output dimensionality. Applying fmap snd
to the result will recover the result of jacobianWith
Instead of returning the Jacobian matrix, the elements of the matrix are combined with the input using the g
.
jacobian'
==jacobianWith'
(_ dx -> dx)
Higher Order Jacobian (Sparse-on-Reverse)
jacobians :: (Traversable f, Functor g, Num a) => (forall s. f (AD s (Sparse a)) -> g (AD s (Sparse a))) -> f a -> g (Cofree f a) Source #
Transposed Jacobians (Forward Mode)
jacobianT :: (Traversable f, Functor g, Num a) => (forall s. f (AD s (Forward a)) -> g (AD s (Forward a))) -> f a -> f (g a) Source #
A fast, simple, transposed Jacobian computed with forward-mode AD.
jacobianWithT :: (Traversable f, Functor g, Num a) => (a -> a -> b) -> (forall s. f (AD s (Forward a)) -> g (AD s (Forward a))) -> f a -> f (g b) Source #
Hessian (Sparse-On-Reverse)
hessian :: (Traversable f, Num a) => (forall s. Reifies s Tape => f (On (Reverse s (Sparse a))) -> On (Reverse s (Sparse a))) -> f a -> f (f a) Source #
Compute the Hessian via the Jacobian of the gradient. gradient is computed in reverse mode and then the Jacobian is computed in sparse (forward) mode.
>>>
hessian (\[x,y] -> x*y) [1,2]
[[0,1],[1,0]]
hessian' :: (Traversable f, Num a) => (forall s. f (AD s (Sparse a)) -> AD s (Sparse a)) -> f a -> (a, f (a, f a)) Source #
Hessian Tensors (Sparse or Sparse-On-Reverse)
hessianF :: (Traversable f, Functor g, Num a) => (forall s. Reifies s Tape => f (On (Reverse s (Sparse a))) -> g (On (Reverse s (Sparse a)))) -> f a -> g (f (f a)) Source #
Compute the order 3 Hessian tensor on a non-scalar-to-non-scalar function using 'Sparse'-on-'Reverse'
>>>
hessianF (\[x,y] -> [x*y,x+y,exp x*cos y]) [1,2 :: RDouble]
[[[0.0,1.0],[1.0,0.0]],[[0.0,0.0],[0.0,0.0]],[[-1.131204383757,-2.471726672005],[-2.471726672005,1.131204383757]]]
Hessian Tensors (Sparse)
hessianF' :: (Traversable f, Functor g, Num a) => (forall s. f (AD s (Sparse a)) -> g (AD s (Sparse a))) -> f a -> g (a, f (a, f a)) Source #
Hessian Vector Products (Forward-On-Reverse)
hessianProduct :: (Traversable f, Num a) => (forall s. Reifies s Tape => f (On (Reverse s (Forward a))) -> On (Reverse s (Forward a))) -> f (a, a) -> f a Source #
computes the product of the hessian hessianProduct
f wvH
of a non-scalar-to-scalar function f
at w =
with a vector fst
$ wvv = snd $ wv
using "Pearlmutter's method" from http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.29.6143, which states:
H v = (d/dr) grad_w (w + r v) | r = 0
Or in other words, we take the directional derivative of the gradient. The gradient is calculated in reverse mode, then the directional derivative is calculated in forward mode.
hessianProduct' :: (Traversable f, Num a) => (forall s. Reifies s Tape => f (On (Reverse s (Forward a))) -> On (Reverse s (Forward a))) -> f (a, a) -> f (a, a) Source #
computes both the gradient of a non-scalar-to-scalar hessianProduct'
f wvf
at w =
and the product of the hessian fst
$ wvH
at w
with a vector v = snd $ wv
using "Pearlmutter's method". The outputs are returned wrapped in the same functor.
H v = (d/dr) grad_w (w + r v) | r = 0
Or in other words, we return the gradient and the directional derivative of the gradient. The gradient is calculated in reverse mode, then the directional derivative is calculated in forward mode.
Derivatives (Forward Mode)
diffF :: (Functor f, Num a) => (forall s. AD s (Forward a) -> f (AD s (Forward a))) -> a -> f a Source #
diffF' :: (Functor f, Num a) => (forall s. AD s (Forward a) -> f (AD s (Forward a))) -> a -> f (a, a) Source #
Derivatives (Tower)
diffsF :: (Functor f, Num a) => (forall s. AD s (Tower a) -> f (AD s (Tower a))) -> a -> f [a] Source #
diffs0F :: (Functor f, Num a) => (forall s. AD s (Tower a) -> f (AD s (Tower a))) -> a -> f [a] Source #
Directional Derivatives (Forward Mode)
du :: (Functor f, Num a) => (forall s. f (AD s (Forward a)) -> AD s (Forward a)) -> f (a, a) -> a Source #
Compute the directional derivative of a function given a zipped up Functor
of the input values and their derivatives
du' :: (Functor f, Num a) => (forall s. f (AD s (Forward a)) -> AD s (Forward a)) -> f (a, a) -> (a, a) Source #
Compute the answer and directional derivative of a function given a zipped up Functor
of the input values and their derivatives
duF :: (Functor f, Functor g, Num a) => (forall s. f (AD s (Forward a)) -> g (AD s (Forward a))) -> f (a, a) -> g a Source #
Compute a vector of directional derivatives for a function given a zipped up Functor
of the input values and their derivatives.
duF' :: (Functor f, Functor g, Num a) => (forall s. f (AD s (Forward a)) -> g (AD s (Forward a))) -> f (a, a) -> g (a, a) Source #
Compute a vector of answers and directional derivatives for a function given a zipped up Functor
of the input values and their derivatives.
Directional Derivatives (Tower)
dus :: (Functor f, Num a) => (forall s. f (AD s (Tower a)) -> AD s (Tower a)) -> f [a] -> [a] Source #
dus0 :: (Functor f, Num a) => (forall s. f (AD s (Tower a)) -> AD s (Tower a)) -> f [a] -> [a] Source #
dusF :: (Functor f, Functor g, Num a) => (forall s. f (AD s (Tower a)) -> g (AD s (Tower a))) -> f [a] -> g [a] Source #
dus0F :: (Functor f, Functor g, Num a) => (forall s. f (AD s (Tower a)) -> g (AD s (Tower a))) -> f [a] -> g [a] Source #
Taylor Series (Tower)
Maclaurin Series (Tower)
maclaurin0 :: Fractional a => (forall s. AD s (Tower a) -> AD s (Tower a)) -> a -> [a] Source #
Gradient Descent
gradientDescent :: (Traversable f, Fractional a, Ord a) => (forall s. Reifies s Tape => f (Reverse s a) -> Reverse s a) -> f a -> [f a] Source #
The gradientDescent
function performs a multivariate
optimization, based on the naive-gradient-descent in the file
stalingrad/examples/flow-tests/pre-saddle-1a.vlad
from the
VLAD compiler Stalingrad sources. Its output is a stream of
increasingly accurate results. (Modulo the usual caveats.)
It uses reverse mode automatic differentiation to compute the gradient.
gradientAscent :: (Traversable f, Fractional a, Ord a) => (forall s. Reifies s Tape => f (Reverse s a) -> Reverse s a) -> f a -> [f a] Source #
Perform a gradient descent using reverse mode automatic differentiation to compute the gradient.
conjugateGradientDescent :: (Traversable f, Ord a, Fractional a) => (forall s. Chosen s => f (Or s (On (Forward (Forward a))) (Kahn a)) -> Or s (On (Forward (Forward a))) (Kahn a)) -> f a -> [f a] Source #
Perform a conjugate gradient descent using reverse mode automatic differentiation to compute the gradient, and using forward-on-forward mode for computing extrema.
>>>
let sq x = x * x
>>>
let rosenbrock [x,y] = sq (1 - x) + 100 * sq (y - sq x)
>>>
rosenbrock [0,0]
1>>>
rosenbrock (conjugateGradientDescent rosenbrock [0, 0] !! 5) < 0.1
True
conjugateGradientAscent :: (Traversable f, Ord a, Fractional a) => (forall s. Chosen s => f (Or s (On (Forward (Forward a))) (Kahn a)) -> Or s (On (Forward (Forward a))) (Kahn a)) -> f a -> [f a] Source #
Perform a conjugate gradient ascent using reverse mode automatic differentiation to compute the gradient.
stochasticGradientDescent :: (Traversable f, Fractional a, Ord a) => (forall s. Reifies s Tape => e -> f (Reverse s a) -> Reverse s a) -> [e] -> f a -> [f a] Source #
The stochasticGradientDescent
function approximates
the true gradient of the constFunction by a gradient at
a single example. As the algorithm sweeps through the training
set, it performs the update for each training example.
It uses reverse mode automatic differentiation to compute the gradient The learning rate is constant through out, and is set to 0.001