Strategie
Class NRU

java.lang.Object
  |
  +--Strategie.ReplaceStrategy
        |
        +--Strategie.NRU

public class NRU

extends ReplaceStrategy

Implementation of the page replacement strategy NRU (Not-recently-used). It is based on Clock and there on FIFO. In addition to Clock, a modifyBit is used, to prefer selecting pages for replacing, that have not been modified recently.

Field Summary

static boolean	ISACCESSCOUNT Number of accesses is not relevant for this strategy.
static boolean	ISACCESSTIME Time of access is not relevant for this strategy.
static boolean	ISINSERTIONTIME Time of insertion is relevant for this strategy.
static java.lang.String	LONGNAME Long name of this streategy.
static int	MODBITCOUNT Number of reference-bits of this strategy.
static int	REFBITCOUNT Number of reference-bits of this strategy.
static java.lang.String	SHORTNAME Short name of this streategy.

Fields inherited from class Strategie.ReplaceStrategy

isAccessCount, isAccessTime, isInsertTime, isShowMemoryDetails, longName, modifyBitCount, referenceBitCount, shortName

Constructor Summary

NRU(boolean showDetails)
Creates a new instance of this strategy.

Method Summary

Memory	createMemory(int size, int refBits, int modBits) Creates a new memory structure with the given size and number of reference- and modifyBits.
int	getDrawLfdNr(Memory memory, int i) Returns the index of the frame i in memory structure.
Page	getVictimPage(Memory memory, SimuData simu, GUI gui) Selects the next victim page.
void	replacePage(Memory memory, Page oldPage, Page newPage, SimuData simu, GUI gui) Replaces the oldPage by the newPage in memory.
void	setInitVictimPointer(Memory memory) Sets the indexpointer to the page that has to be placed first.
void	sortMemory(Memory memory) Sorts the memory by insertiontime of each page.

Methods inherited from class Strategie.ReplaceStrategy

getLongName, getModifyBitCount, getReferenceBitCount, getShortName, isAccessCount, isAccessTime, isInsertTime, isModifyBit, isReferenceBit, isShowMemoryDetails, reInsertPage, setShowMemoryDetails

Methods inherited from class java.lang.Object

, clone, equals, finalize, getClass, hashCode, notify, notifyAll, registerNatives, toString, wait, wait, wait

Field Detail

SHORTNAME

public static final java.lang.String SHORTNAME

Short name of this streategy.

LONGNAME

public static final java.lang.String LONGNAME

Long name of this streategy.

REFBITCOUNT

public static final int REFBITCOUNT

Number of reference-bits of this strategy.

MODBITCOUNT

public static final int MODBITCOUNT

Number of reference-bits of this strategy.

ISACCESSCOUNT

public static final boolean ISACCESSCOUNT

Number of accesses is not relevant for this strategy.

ISACCESSTIME

public static final boolean ISACCESSTIME

Time of access is not relevant for this strategy.

ISINSERTIONTIME

public static final boolean ISINSERTIONTIME

Time of insertion is relevant for this strategy.

Constructor Detail

NRU

public NRU(boolean showDetails)

Creates a new instance of this strategy.

Method Detail

createMemory

public Memory createMemory(int size,
                           int refBits,
                           int modBits)

Creates a new memory structure with the given size and number of reference- and modifyBits.

Overrides:

createMemory in class ReplaceStrategy

setInitVictimPointer

public void setInitVictimPointer(Memory memory)

Sets the indexpointer to the page that has to be placed first. Only needed at the beginning when creating new memory.

Overrides:

setInitVictimPointer in class ReplaceStrategy

sortMemory

public void sortMemory(Memory memory)

Sorts the memory by insertiontime of each page. Caution: For a simple solution the old framenumber will be overwritten.

Overrides:

sortMemory in class ReplaceStrategy

getDrawLfdNr

public int getDrawLfdNr(Memory memory,
                        int i)

Returns the index of the frame i in memory structure. The memory structure can have an strategy-dependant internal sort. This is needed for drawing the memory details in the strategy-dependant order.

Overrides:

getDrawLfdNr in class ReplaceStrategy

getVictimPage

public Page getVictimPage(Memory memory,
                          SimuData simu,
                          GUI gui)

Selects the next victim page. It's the oldest page in memory.

Overrides:

getVictimPage in class ReplaceStrategy

replacePage

public void replacePage(Memory memory,
                        Page oldPage,
                        Page newPage,
                        SimuData simu,
                        GUI gui)

Replaces the oldPage by the newPage in memory.

Overrides:

replacePage in class ReplaceStrategy