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.

Since: 0.5.0.0

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.

Since: 0.5.0.0

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

Since: 0.5.1.0

Methods

rnf :: Decision -> ()

tidOf :: ThreadId -> Decision -> ThreadId

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

Since: 0.5.0.0

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.

Since: 0.5.0.0

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.

Since: 0.5.0.0

roundRobinSched :: Scheduler ()

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

Since: 0.5.0.0

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.

Since: 0.5.0.0

roundRobinSchedNP :: Scheduler ()

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

Since: 0.5.0.0

Utilities

makeNonPreemptive :: Scheduler s -> Scheduler s

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

Since: 0.5.0.0