batching (empty) → 0.1.0.0
raw patch · 5 files changed
+594/−0 lines, 5 filesdep +QuickCheckdep +basedep +batching
Dependencies added: QuickCheck, base, batching, primitive, short-vec, sint, test-framework, test-framework-quickcheck2
Files
- CHANGELOG.md +4/−0
- LICENSE +202/−0
- batching.cabal +62/−0
- src/Control/Batching.hs +274/−0
- test/Main.hs +52/−0
+ CHANGELOG.md view
@@ -0,0 +1,4 @@+# 0.1.0.0++Initial version.+
+ LICENSE view
@@ -0,0 +1,202 @@++ Apache License+ Version 2.0, January 2004+ http://www.apache.org/licenses/++ TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION++ 1. Definitions.++ "License" shall mean the terms and conditions for use, reproduction,+ and distribution as defined by Sections 1 through 9 of this document.++ "Licensor" shall mean the copyright owner or entity authorized by+ the copyright owner that is granting the License.++ "Legal Entity" shall mean the union of the acting entity and all+ other entities that control, are controlled by, or are under common+ control with that entity. 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+ batching.cabal view
@@ -0,0 +1,62 @@+cabal-version: 1.12++-- This file has been generated from package.yaml by hpack version 0.33.0.+--+-- see: https://github.com/sol/hpack+--+-- hash: 8936a5cb6e45b5103dfe0d29f00e470867581f0bfafd31536c356315143191dd++name: batching+version: 0.1.0.0+synopsis: An Applicative Functor deferring actions to run in a batch later.+description: This provides the type Batching, an Applicative which defers request-response+ exchanges of a fixed type, to be performed in a single batch. This means you+ can write code that appears to issue requests and immediately receive their+ responses, but process the requests jointly all at once.+category: Algorithms+homepage: https://github.com/google/hs-batching#readme+bug-reports: https://github.com/google/hs-batching/issues+author: Andrew Pritchard <awpr@google.com>+maintainer: Andrew Pritchard <awpr@google.com>+copyright: 2019-2021 Google LLC+license: Apache-2.0+license-file: LICENSE+build-type: Simple+extra-source-files:+ CHANGELOG.md++source-repository head+ type: git+ location: https://github.com/google/hs-batching++library+ exposed-modules:+ Control.Batching+ other-modules:+ Paths_batching+ hs-source-dirs:+ src+ build-depends:+ base >=4.12 && <4.16+ , primitive >=0.1 && <0.8+ , short-vec >=0.1 && <0.2+ , sint >=0.1 && <0.2+ default-language: Haskell2010++test-suite Batching-test+ type: exitcode-stdio-1.0+ main-is: Main.hs+ other-modules:+ Paths_batching+ hs-source-dirs:+ test+ build-depends:+ QuickCheck+ , base >=4.12 && <4.16+ , batching+ , primitive >=0.1 && <0.8+ , short-vec+ , sint >=0.1 && <0.2+ , test-framework+ , test-framework-quickcheck2+ default-language: Haskell2010
+ src/Control/Batching.hs view
@@ -0,0 +1,274 @@+-- Copyright 2019-2021 Google LLC+--+-- Licensed under the Apache License, Version 2.0 (the "License");+-- you may not use this file except in compliance with the License.+-- You may obtain a copy of the License at+--+-- http://www.apache.org/licenses/LICENSE-2.0+--+-- Unless required by applicable law or agreed to in writing, software+-- distributed under the License is distributed on an "AS IS" BASIS,+-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.+-- See the License for the specific language governing permissions and+-- limitations under the License.++{-# LANGUAGE AllowAmbiguousTypes #-}+{-# LANGUAGE BangPatterns #-}+{-# LANGUAGE DataKinds #-}+{-# LANGUAGE FlexibleContexts #-}+{-# LANGUAGE GADTs #-}+{-# LANGUAGE KindSignatures #-}+{-# LANGUAGE MagicHash #-}+{-# LANGUAGE RankNTypes #-}+{-# LANGUAGE ScopedTypeVariables #-}+{-# LANGUAGE TypeApplications #-}+{-# LANGUAGE TypeOperators #-}++-- | An 'Applicative' for deferring "requests" to handle them all in bulk.++module Control.Batching+ ( Batching, request, batchRequest, runBatching, runBatching_+ ) where++import Control.Applicative (Applicative(..))+import Control.Monad.ST (runST)+import Data.Foldable (sequenceA_, toList)+import qualified Data.Foldable as F+import Data.Functor.Identity (Identity(..))+import GHC.TypeNats (type (+), Nat)++import qualified Data.Primitive.Array as A+import Data.SInt (SInt(unSInt), reifySInt, withSInt, sintVal, addSInt)+import Data.Vec.Short (Vec)+import qualified Data.Vec.Short as Vec++-- Quick-and-dirty Vec builder standin: a list.+--+-- Supports O(1) cons, O(n) conversion to Vec, and O(m) prepend of length-m to+-- length-n.+--+-- Note we won't ever left-associate appends, because we design the 'Batching'+-- type to avoid it, so O(m) prepend won't lead to any super-linear behavior.+newtype VecBuilder (n :: Nat) a = VecBuilder+ { _vbContents :: [a]+ }++nil :: VecBuilder 0 a+nil = VecBuilder []++cons :: a -> VecBuilder n a -> VecBuilder (1+n) a+cons x (VecBuilder xs) = VecBuilder (x:xs)++vbToVec' :: SInt n -> VecBuilder n a -> Vec n a+vbToVec' n (VecBuilder c) = reifySInt n $ Vec.fromList c++-- Quick-and-dirty Vec iterator standin: a list.+--+-- Supports O(1) uncons, O(m) bulk-uncons (split) of length m, and O(n)+-- conversion from Vec.+--+-- Note we won't ever recursively split, since splits are only generated by+-- 'batchRequest', and not by ('<*>'); so O(m) split won't lead to any+-- super-linear behavior.+newtype VecView (n :: Nat) a = VecView { _unVecView :: [a] }++uncons :: VecView (1+n) a -> (a, VecView n a)+uncons (VecView (x:xs)) = (x, VecView xs)+uncons _ = error "Internal error: invalid VecView."++split+ :: forall m n a. SInt m -> VecView (m+n) a -> (VecView m a, VecView n a)+split m (VecView xs) =+ let (ma, na) = splitAt (unSInt m) xs+ in (VecView ma, VecView na)++vvFromVec :: Vec n a -> VecView n a+vvFromVec = VecView . toList++-- TODO(awpr): consider factoring out a @SizedBatch n rq rs a@ type and+-- providing a scoped API for accessing it, e.g.:+--+-- withSizedBatch+-- :: Batching rq rs a+-- -> (forall n. KnownNat n => SizedBatch n rq rs a -> r)+-- -> r+-- getBatchRequests :: SizedBatch n rq rs a -> Vec n rq+-- putBatchResponses :: SizedBatch n rq rs a -> Vec n rs -> a++-- -- Start with a simple version: contains the requests and a function to --+-- consume the responses.+-- data Batching0 rq rs a = forall n. Batching0+-- { n :: SInt n+-- , requests :: VecBuilder n rq+-- , cont :: VecView n rs -> a+-- }+--+-- -- First transformation: actually use the curried (<**>) type internally so+-- -- that we can right-associate all of the request prepends.+-- newtype Batching1 rq rs a = Batching1+-- { _unBatching1 :: forall r. Batching0 rq rs (a -> r) -> Batching0 rq rs r+-- }+--+-- -- Second transformation: turn the above function inside out, to enable the+-- -- third transformation.+-- newtype Batching2 rq rs a = Batching2+-- { _unBatching2+-- :: forall z r. (Batching0 rq rs r -> z) -> (Batching0 rq rs (a -> r) -> z)+-- }+--+-- -- Third transformation: curry both of the function types above to get rid+-- -- of a GADT constructor.+-- newtype Batching rq rs a = Batching+-- { _unBatching+-- :: forall z r+-- . (forall n. SInt n -> (VecView n rs -> r) -> VecBuilder n rq -> z)+-- -> (forall m. SInt m -> (VecView m rs -> a -> r) -> VecBuilder m rq -> z)+-- }+--+-- Now we have a newtype Batching that:+-- - takes a continuation for what to do with a VecBuilder of requests and a+-- VecView-consuming function returning @r@, with matching lengths.+-- - takes a VecView-consuming function for a (smaller) VecView returning+-- @a -> r@.+-- - takes a (smaller) VecBuilder of requests.+-- - wraps the VecView-consuming function with code to consume a prefix and+-- apply away the @a@ parameter.+-- - prepends some of its own requests to the VecBuilder.+-- - passes them on to the continuation and returns its result.++-- | The bulk request-response Applicative.+--+-- A value of type @Batching rq rs a@ describes a computation that gathers some+-- number of @rq@ request values, expects the same number of @rs@ response+-- values, and ultimately returns an @a@ result value derived from the+-- responses.+--+-- This can be used to apply an offline resource allocation algorithm to code+-- written as if allocation requests were satisfied incrementally.+--+-- This synergizes well with @-XApplicativeDo@, which allows using do-notation+-- for this type, as long as requests do not depend on earlier responses.+newtype Batching rq rs a = Batching+-- This is essentially the same as the Ap type from+-- Control.Applicative.Free.Fast, but specialized to lists of requests and+-- responses.+ { _unBulk+ :: forall z r+ . (forall n. SInt n -> (VecView n rs -> r) -> VecBuilder n rq -> z)+ -> (forall m. SInt m -> (VecView m rs -> a -> r) -> VecBuilder m rq -> z)+ }++instance Functor (Batching rq rs) where+ fmap f (Batching go) = Batching $ \k m g rqs -> go k m (\vv x -> g vv (f x)) rqs+ {-# INLINE fmap #-}++instance Applicative (Batching rq rs) where+ pure x = Batching $ \k m g rqs -> k m (`g` x) rqs+ {-# INLINE pure #-}+ Batching f <*> Batching x =+ Batching $ \k m g rqs -> f (x k) m (\vv h -> g vv . h) rqs+ {-# INLINE (<*>) #-}+ liftA2 f (Batching x) (Batching y) = Batching $ \k m g rqs ->+ x (y k) m (\vv a b -> g vv (f a b)) rqs+ {-# INLINE liftA2 #-}++-- | Issue one request and retrieve its response.+request :: rq -> Batching rq rs rs+request rq = Batching $ \k n g !rqs -> k+ (sintVal `addSInt` n)+ -- Consume our response off the front of the VecView and pass it to the+ -- result function.+ (\rss -> let !(rs, rss') = uncons rss in g rss' rs)+ -- Add our request to the front of the VecBuilder.+ (rq `cons` rqs)+{-# INLINE request #-}++-- Specialized implementation for issuing Traversables of requests at once.+-- The goal here is to separate the traversal gathering requests from the+-- traversal building up the result, so we don't have to allocate a bunch of+-- memory to hold a closure that will build the resulting data structure while+-- we're handling the requests.+newtype BulkCont rq rs a = BulkCont+ { _bcCont :: A.Array rs -> Int -> (Int, a)+ }++instance Functor (BulkCont rq rs) where+ fmap f (BulkCont k) = BulkCont (\a i ->+ let !(i', x) = k a i+ in (i', f x))+ {-# INLINE fmap #-}++instance Applicative (BulkCont rq rs) where+ pure x = BulkCont (\_ i -> (i, x))+ {-# INLINE pure #-}++ BulkCont kf <*> BulkCont kx = BulkCont (\a i ->+ let !(i', f) = kf a i+ !(i'', x) = kx a i'+ in (i'', f x))+ {-# INLINE (<*>) #-}++ liftA2 f (BulkCont kx) (BulkCont ky) = BulkCont (\a i ->+ let !(i', x) = kx a i+ !(i'', y) = ky a i'+ in (i'', f x y))+ {-# INLINE liftA2 #-}++rqBulkCont :: rq -> BulkCont rq rs rs+rqBulkCont _ = BulkCont $ \a i ->+ case A.indexArrayM a i of ((), x) -> (1 + i, x)+{-# INLINE rqBulkCont #-}++vvToArray :: forall n a. SInt n -> VecView n a -> A.Array a+vvToArray n (VecView v) = runST $+ A.newArray (unSInt n) undefined >>= \arr -> do+ sequenceA_ $ zipWith (A.writeArray arr) [0..] v+ A.unsafeFreezeArray arr++-- | Issue a Traversable of requests and retrieve their responses.+batchRequest :: forall t rq rs. Traversable t => t rq -> Batching rq rs (t rs)+batchRequest rqs0 =+ let !rqs = \rest -> F.foldr (:) rest rqs0+ !n = length rqs0+ in withSInt n $ \sn ->+ Batching $ \k m g (VecBuilder rqs1) -> k+ (sn `addSInt` m)+ (\rss ->+ let !(rss0, rss1) = split sn rss+ !(_, rssT) =+ _bcCont (traverse rqBulkCont rqs0) (vvToArray sn rss0) 0+ in g rss1 rssT)+ (VecBuilder (rqs rqs1))+{-# INLINE batchRequest #-}++-- | Given an allocator function in any 'Functor', run a 'Batching' computation.+runBatching+ :: Functor f+ => (forall n. Vec n rq -> f (Vec n rs))+ -> Batching rq rs a -> f a+runBatching f (Batching go) = go+ (\n q rqs -> q . vvFromVec <$> f (vbToVec' n rqs))+ sintVal+ (const id)+ nil+{-# INLINE runBatching #-}++-- | Like 'runBatching', but without a 'Functor' (or implicitly in 'Identity').+runBatching_ :: (forall n. Vec n rq -> Vec n rs) -> Batching rq rs a -> a+runBatching_ f = runIdentity . runBatching (Identity . f)+{-# INLINE runBatching_ #-}++-- TODO(awpr): consider adding a Batched monad that supports many batches of+-- requests:+--+-- type Batched rq rs a = Free (Batching rq rs) a+--+-- -- Use ApplicativeDo inside this to group requests into a batch.+-- batch :: Batching rq rs a -> Batched rq rs a+--+-- -- Note this requires Monad rather than just Functor, since it can have+-- multiple batches.+-- runBatched+-- :: Monad f+-- => (forall n. KnownNat n => Vec n rq -> f (Vec n rs))+-- -> Batched rq rs a -> f a
+ test/Main.hs view
@@ -0,0 +1,52 @@+-- Copyright 2021 Google LLC+--+-- Licensed under the Apache License, Version 2.0 (the "License");+-- you may not use this file except in compliance with the License.+-- You may obtain a copy of the License at+--+-- http://www.apache.org/licenses/LICENSE-2.0+--+-- Unless required by applicable law or agreed to in writing, software+-- distributed under the License is distributed on an "AS IS" BASIS,+-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.+-- See the License for the specific language governing permissions and+-- limitations under the License.++{-# LANGUAGE RankNTypes #-}+{-# LANGUAGE ScopedTypeVariables #-}+{-# LANGUAGE TypeApplications #-}++module Main where++import Data.Functor.Const (Const(..))++import Test.Framework (defaultMain)+import Test.Framework.Providers.QuickCheck2 (testProperty)+import Test.QuickCheck ((===), forAllBlind, arbitrary)++import Data.Vec.Short (rev)++import Control.Batching++main :: IO ()+main = defaultMain+ [ testProperty "deferred map" $ forAllBlind (arbitrary @(Int -> Int)) $+ \f xs ->+ runBatching_ (fmap f) (traverse request xs) === map f xs++ , testProperty "deferred map2" $ forAllBlind (arbitrary @(Int -> Int)) $+ \f xss ->+ runBatching_ (fmap f) (traverse batchRequest xss) ===+ map (map f) xss++ , testProperty "roundabout reverse" $ \ (xs :: [Int]) ->+ runBatching_ rev (traverse request xs) === reverse xs++ , testProperty "list?" $ \ (xs :: [Int]) ->+ runBatching (\rqs -> [rqs, rev rqs]) (traverse request xs) ===+ [xs, reverse xs]++ , testProperty "silliness" $ \ (xs :: [Int]) ->+ runBatching (\rqs -> Const (length rqs)) (traverse request xs) ===+ Const (length xs)+ ]