kdbopmphmpredictor.h File Reference

Defines for the Order Preserving Minimal Perfect Hash Map Predictor. More...

#include <stdint.h>

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Enumerations
enum	predictorflag_t { OPMPHM_PREDICTOR_FLAG_MMAP_STRUCT = 1 , OPMPHM_PREDICTOR_FLAG_MMAP_PATTERNTABLE = 1 << 2 }
	OpmphmPredictor Flags. More...

Functions
OpmphmPredictor *	opmphmPredictorNew (void)
	Basic functions. More...
void	opmphmPredictorDel (OpmphmPredictor *op)
	Deletes the OpmphmPredictor. More...
void	opmphmPredictorCopy (OpmphmPredictor *dest, OpmphmPredictor *source)
	Make a copy of the OpmphmPredictor. More...
size_t	opmphmPredictorWorthOpmphm (size_t n)
	Heuristic function. More...
int	opmphmPredictor (OpmphmPredictor *op, size_t n)
	Predictor functions. More...
void	opmphmPredictorIncCountOpmphm (OpmphmPredictor *op)
	Increases the counter when the OPMPHM was used for the ksLookup (...) . More...
int	opmphmPredictorIncCountBinarySearch (OpmphmPredictor *op, size_t n)
	Increases the counter when the Binary Search was used for the ksLookup (...) . More...

Variables
const uint16_t	opmphmPredictorHistoryMask
	Order Preserving Minimal Perfect Hash Map Predictor. More...
const size_t	opmphmPredictorActionLimit
	The opmphmPredictorActionLimit define the minimum KeySet size necessary for predictor actions.

Detailed Description

Defines for the Order Preserving Minimal Perfect Hash Map Predictor.

Copyright

BSD License (see doc/COPYING or https://www.libelektra.org)

Enumeration Type Documentation

predictorflag_t

enum predictorflag_t

OpmphmPredictor Flags.

Enumerator
OPMPHM_PREDICTOR_FLAG_MMAP_STRUCT	OpmphmPredictor struct lies inside a mmap region. This flag is set for OpmphmPredictor structs inside a mapped region. It prevents erroneous free() calls on these OpmphmPredictors.
OPMPHM_PREDICTOR_FLAG_MMAP_PATTERNTABLE	OpmphmPredictor patternTable lies inside a mmap region. This flag is set for OpmphmPredictor patternTables inside a mapped region. It prevents erroneous free() calls on these patternTables.

Function Documentation

opmphmPredictor()

int opmphmPredictor	(	OpmphmPredictor *	op,
		size_t	n
	)

Predictor functions.

Predictor functions.

Uses the opmphmPredictorWorthOpmphm (...) to check if the previous sequence of ksLookup (...) invocations without alteration was worth using the OPMPHM. Updates the state with the predictionAutomata and the worth information of the previous history. Alters the history with the worth information and makes the prediction for the next sequence of ksLookup (...) invocations.

Parameters

op	the Predictor
n	the number of elements in the KeySet

Return values

1	it is worth using the OPMPHM
0	it is not worth using the OPMPHM

opmphmPredictorCopy()

void opmphmPredictorCopy	(	OpmphmPredictor *	dest,
		OpmphmPredictor *	source
	)

Make a copy of the OpmphmPredictor.

Parameters

source	the OpmphmPredictor source
dest	the OpmphmPredictor destination

opmphmPredictorDel()

void opmphmPredictorDel

(

OpmphmPredictor *

op

)

Deletes the OpmphmPredictor.

Clears and frees all memory in OpmphmPredictor.

Parameters

op	the OpmphmPredictor

opmphmPredictorIncCountBinarySearch()

int opmphmPredictorIncCountBinarySearch ( OpmphmPredictor *  op, size_t  n  )

inline

Increases the counter when the Binary Search was used for the ksLookup (...) .

Prevents also an endless Binary Search usage by a simple heuristic.

Parameters

op	the Predictor
n	the number of elements in the KeySet

Return values

1	it is worth using the OPMPHM
0	it is not worth using the OPMPHM

opmphmPredictorIncCountOpmphm()

void opmphmPredictorIncCountOpmphm ( OpmphmPredictor *  op )

inline

Increases the counter when the OPMPHM was used for the ksLookup (...) .

Parameters

op	the Predictor

opmphmPredictorNew()

OpmphmPredictor* opmphmPredictorNew

(

void

)

Basic functions.

Basic functions.

Reserves for all possible values of opmphmPredictorHistoryMask two bits to store all 4 states of the Prediction Automata A2. Sets the initial state to 0.

Return values

OpmphmPredictor	* success
NULL	memory error

opmphmPredictorWorthOpmphm()

size_t opmphmPredictorWorthOpmphm ( size_t  n )

inline

Heuristic function.

Heuristic function.

This easy and fast computable heuristic function tells how many ksLookup (...) invocations without alteration of the KeySet need to be made to justify the OPMPHM usage. This heuristic function is developed and measured by benchmarks.

Parameters

n	the number of elements in the KeySet

Return values

size_t

the heuristic value

Variable Documentation

opmphmPredictorHistoryMask

const uint16_t opmphmPredictorHistoryMask

extern

Order Preserving Minimal Perfect Hash Map Predictor.

A modified Global History Register and Global Pattern History Table branch prediction algorithm from

Tse-Yu Yeh and Yale N. Patt "Alternative Implementations of Two-Level Adaptive Branch Prediction" In: The 19th Annual International Symposium on Computer Architecture (1992), pp. 124-134

Maps the event of branch taken or not to a sequence of ksLookup (...) invocations without KeySet alteration that is worth using the OPMPHM or not. The predictor looks at past events to predict the future, to keep track of past events the lookupCount and the ksSize must be stored. opmphmPredictorHistoryMask defines the length and extraction mask of the global history register interpreted binary it must be a series of 1, with a minimum value of 0x3 and a maximum value of 0x7FFF.

Order Preserving Minimal Perfect Hash Map Predictor.