Simulation.Aivika.Resource.Preemption.Base

Tested with: GHC 7.10.1

This module defines the preemptible resource.

The module is optimised in the sense that this kind of the resource has neither additional signals, nor counters that would may slow down the simulation.

Resource Type

data Resource

Represents a preemptible resource.

Instances

Eq Resource

Creating Resource

newResource

Arguments

:: Int

the initial count (and maximal count too) of the resource

-> Simulation Resource

Create a new resource with the specified initial count that becomes the upper bound as well.

newResourceWithMaxCount

Arguments

:: Int

the initial count of the resource

-> Maybe Int

the maximum count of the resource, which can be indefinite

-> Simulation Resource

Create a new resource with the specified initial and maximum counts, where Nothing means that the resource has no upper bound.

Resource Properties

resourceMaxCount :: Resource -> Maybe Int

Return the maximum count of the resource, where Nothing means that the resource has no upper bound.

resourceCount :: Resource -> Event Int

Return the current count of the resource.

Requesting for and Releasing Resource

requestResourceWithPriority

Arguments

:: Resource

the requested resource

-> Double

the priority (the less value has a higher priority)

-> Process ()

Request with the priority for the resource decreasing its count in case of success, otherwise suspending the discontinuous process until some other process releases the resource.

It may preempt another process if the latter aquired the resource before but had a lower priority. Then the current process takes an ownership of the resource.

releaseResource

Arguments

:: Resource

the resource to release

-> Process ()

Release the resource increasing its count and resuming one of the previously suspended or preempted processes as possible.

usingResourceWithPriority

Arguments

:: Resource

the resource we are going to request for and then release in the end

-> Double

the priority (the less value has a higher priority)

-> Process a

the action we are going to apply having the resource

-> Process a

the result of the action

Acquire the resource with the specified priority, perform some action and safely release the resource in the end, even if the IOException was raised within the action.

Altering Resource

incResourceCount

Arguments

:: Resource

the resource

-> Int

the increment for the resource count

-> Event ()

Increase the count of available resource by the specified number, invoking the awaiting and preempted processes according to their priorities as needed.

decResourceCount

Arguments

:: Resource

the resource

-> Int

the decrement for the resource count

-> Event ()

Decrease the count of available resource by the specified number, preempting the processes according to their priorities as needed.

alterResourceCount

Arguments

:: Resource

the resource

-> Int

a change of the resource count

-> Event ()

Alter the resource count either increasing or decreasing it by calling incResourceCount or decResourceCount respectively.