Test.DejaFu.Schedule

Scheduling for concurrent computations.

Scheduling

type Scheduler state = [(Decision, ThreadAction)] -> Maybe (ThreadId, ThreadAction) -> NonEmpty (ThreadId, Lookahead) -> state -> (Maybe ThreadId, state)

A Scheduler drives the execution of a concurrent program. The parameters it takes are:

1. The trace so far.
2. The last thread executed (if this is the first invocation, this is Nothing).
3. The runnable threads at this point.
4. The state.

It returns a thread to execute, or Nothing if execution should abort here, and also a new state.

data Decision

Scheduling decisions are based on the state of the running program, and so we can capture some of that state in recording what specific decision we made.

Constructors

Start ThreadId

Start a new thread, because the last was blocked (or it's the start of computation).

Continue

Continue running the last thread for another step.

SwitchTo ThreadId

Pre-empt the running thread, and switch to another.

Instances

Eq Decision

Methods

(==) :: Decision -> Decision -> Bool

(/=) :: Decision -> Decision -> Bool

Show Decision

Methods

showsPrec :: Int -> Decision -> ShowS

show :: Decision -> String

showList :: [Decision] -> ShowS

NFData Decision

Methods

rnf :: Decision -> ()

tidOf :: ThreadId -> Decision -> ThreadId

Get the resultant thread identifier of a Decision, with a default case for Continue.

decisionOf

Arguments

:: Foldable f

=> Maybe ThreadId

The prior thread.

-> f ThreadId

The runnable threads.

-> ThreadId

The current thread.

-> Decision

Get the Decision that would have resulted in this thread identifier, given a prior thread (if any) and list of runnable threads.

data NonEmpty a :: * -> *

Non-empty (and non-strict) list type.

Since: 4.9.0.0

Constructors

a :| [a] infixr 5

Instances

Monad NonEmpty

Methods

(>>=) :: NonEmpty a -> (a -> NonEmpty b) -> NonEmpty b

(>>) :: NonEmpty a -> NonEmpty b -> NonEmpty b

return :: a -> NonEmpty a

fail :: String -> NonEmpty a

Functor NonEmpty

Methods

fmap :: (a -> b) -> NonEmpty a -> NonEmpty b

(<$) :: a -> NonEmpty b -> NonEmpty a

MonadFix NonEmpty

Methods

mfix :: (a -> NonEmpty a) -> NonEmpty a

Applicative NonEmpty

Methods

pure :: a -> NonEmpty a

(<*>) :: NonEmpty (a -> b) -> NonEmpty a -> NonEmpty b

(*>) :: NonEmpty a -> NonEmpty b -> NonEmpty b

(<*) :: NonEmpty a -> NonEmpty b -> NonEmpty a

Foldable NonEmpty

Methods

fold :: Monoid m => NonEmpty m -> m

foldMap :: Monoid m => (a -> m) -> NonEmpty a -> m

foldr :: (a -> b -> b) -> b -> NonEmpty a -> b

foldr' :: (a -> b -> b) -> b -> NonEmpty a -> b

foldl :: (b -> a -> b) -> b -> NonEmpty a -> b

foldl' :: (b -> a -> b) -> b -> NonEmpty a -> b

foldr1 :: (a -> a -> a) -> NonEmpty a -> a

foldl1 :: (a -> a -> a) -> NonEmpty a -> a

toList :: NonEmpty a -> [a]

null :: NonEmpty a -> Bool

length :: NonEmpty a -> Int

elem :: Eq a => a -> NonEmpty a -> Bool

maximum :: Ord a => NonEmpty a -> a

minimum :: Ord a => NonEmpty a -> a

sum :: Num a => NonEmpty a -> a

product :: Num a => NonEmpty a -> a

Traversable NonEmpty

Methods

traverse :: Applicative f => (a -> f b) -> NonEmpty a -> f (NonEmpty b)

sequenceA :: Applicative f => NonEmpty (f a) -> f (NonEmpty a)

mapM :: Monad m => (a -> m b) -> NonEmpty a -> m (NonEmpty b)

sequence :: Monad m => NonEmpty (m a) -> m (NonEmpty a)

Generic1 NonEmpty

Associated Types

type Rep1 (NonEmpty :: * -> *) :: * -> *

Methods

from1 :: NonEmpty a -> Rep1 NonEmpty a

to1 :: Rep1 NonEmpty a -> NonEmpty a

MonadZip NonEmpty

Methods

mzip :: NonEmpty a -> NonEmpty b -> NonEmpty (a, b)

mzipWith :: (a -> b -> c) -> NonEmpty a -> NonEmpty b -> NonEmpty c

munzip :: NonEmpty (a, b) -> (NonEmpty a, NonEmpty b)

IsList (NonEmpty a)

Associated Types

type Item (NonEmpty a) :: *

Methods

fromList :: [Item (NonEmpty a)] -> NonEmpty a

fromListN :: Int -> [Item (NonEmpty a)] -> NonEmpty a

toList :: NonEmpty a -> [Item (NonEmpty a)]

Eq a => Eq (NonEmpty a)

Methods

(==) :: NonEmpty a -> NonEmpty a -> Bool

(/=) :: NonEmpty a -> NonEmpty a -> Bool

Data a => Data (NonEmpty a)

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> NonEmpty a -> c (NonEmpty a)

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (NonEmpty a)

toConstr :: NonEmpty a -> Constr

dataTypeOf :: NonEmpty a -> DataType

dataCast1 :: Typeable (* -> *) t => (forall d. Data d => c (t d)) -> Maybe (c (NonEmpty a))

dataCast2 :: Typeable (* -> * -> *) t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (NonEmpty a))

gmapT :: (forall b. Data b => b -> b) -> NonEmpty a -> NonEmpty a

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> NonEmpty a -> r

gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> NonEmpty a -> r

gmapQ :: (forall d. Data d => d -> u) -> NonEmpty a -> [u]

gmapQi :: Int -> (forall d. Data d => d -> u) -> NonEmpty a -> u

gmapM :: Monad m => (forall d. Data d => d -> m d) -> NonEmpty a -> m (NonEmpty a)

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> NonEmpty a -> m (NonEmpty a)

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> NonEmpty a -> m (NonEmpty a)

Ord a => Ord (NonEmpty a)

Methods

compare :: NonEmpty a -> NonEmpty a -> Ordering

(<) :: NonEmpty a -> NonEmpty a -> Bool

(<=) :: NonEmpty a -> NonEmpty a -> Bool

(>) :: NonEmpty a -> NonEmpty a -> Bool

(>=) :: NonEmpty a -> NonEmpty a -> Bool

max :: NonEmpty a -> NonEmpty a -> NonEmpty a

min :: NonEmpty a -> NonEmpty a -> NonEmpty a

Read a => Read (NonEmpty a)

Methods

readsPrec :: Int -> ReadS (NonEmpty a)

readList :: ReadS [NonEmpty a]

readPrec :: ReadPrec (NonEmpty a)

readListPrec :: ReadPrec [NonEmpty a]

Show a => Show (NonEmpty a)

Methods

showsPrec :: Int -> NonEmpty a -> ShowS

show :: NonEmpty a -> String

showList :: [NonEmpty a] -> ShowS

Generic (NonEmpty a)

Associated Types

type Rep (NonEmpty a) :: * -> *

Methods

from :: NonEmpty a -> Rep (NonEmpty a) x

to :: Rep (NonEmpty a) x -> NonEmpty a

Semigroup (NonEmpty a)

Methods

(<>) :: NonEmpty a -> NonEmpty a -> NonEmpty a

sconcat :: NonEmpty (NonEmpty a) -> NonEmpty a

stimes :: Integral b => b -> NonEmpty a -> NonEmpty a

NFData a => NFData (NonEmpty a)

Since: 1.4.2.0

Methods

rnf :: NonEmpty a -> ()

type Rep1 NonEmpty

type Rep1 NonEmpty = D1 (MetaData "NonEmpty" "Data.List.NonEmpty" "base" False) (C1 (MetaCons ":|" (InfixI RightAssociative 5) False) ((:*:) (S1 (MetaSel (Nothing Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) Par1) (S1 (MetaSel (Nothing Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec1 []))))

type Rep (NonEmpty a)

type Rep (NonEmpty a) = D1 (MetaData "NonEmpty" "Data.List.NonEmpty" "base" False) (C1 (MetaCons ":|" (InfixI RightAssociative 5) False) ((:*:) (S1 (MetaSel (Nothing Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 a)) (S1 (MetaSel (Nothing Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 [a]))))

type Item (NonEmpty a)

type Item (NonEmpty a) = a

Preemptive

randomSched :: RandomGen g => Scheduler g

A simple random scheduler which, at every step, picks a random thread to run.

roundRobinSched :: Scheduler ()

A round-robin scheduler which, at every step, schedules the thread with the next ThreadId.

Non-preemptive

randomSchedNP :: RandomGen g => Scheduler g

A random scheduler which doesn't preempt the running thread. That is, if the last thread scheduled is still runnable, run that, otherwise schedule randomly.

roundRobinSchedNP :: Scheduler ()

A round-robin scheduler which doesn't preempt the running thread.

Utilities

makeNonPreemptive :: Scheduler s -> Scheduler s

Turn a potentially preemptive scheduler into a non-preemptive one.