opmphmpredictor.c File Reference

The Order Preserving Minimal Perfect Hash Map Predictor. More...

#include <kdbassert.h>
#include <kdbhelper.h>
#include <kdblogger.h>
#include <kdbopmphmpredictor.h>
#include <kdbprivate.h>
#include <stdlib.h>
#include <string.h>

Include dependency graph for opmphmpredictor.c:

Functions
size_t	opmphmPredictorWorthOpmphm (size_t n)
	Heuristic function above the OPMPHM usage is worth. 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...
int	opmphmPredictor (OpmphmPredictor *op, size_t n)
	Predictcs at the first ksLookup (...) after a KeySet changed if it will be worth using the OPMPHM. More...
OpmphmPredictor *	opmphmPredictorNew (void)
	Allocates and initializes the OpmphmPredictor. More...
void	opmphmPredictorCopy (OpmphmPredictor *dest, OpmphmPredictor *source)
	Make a copy of the OpmphmPredictor. More...
void	opmphmPredictorDel (OpmphmPredictor *op)
	Deletes the OpmphmPredictor. More...

Variables
const uint16_t	opmphmPredictorHistoryMask = 0x1FF
	The benchmarked and evaluated values of the predictors configuration. More...
const size_t	opmphmPredictorActionLimit = 599
	The opmphmPredictorActionLimit define the minimum KeySet size necessary for predictor actions.

Detailed Description

The Order Preserving Minimal Perfect Hash Map Predictor.

Copyright

BSD License (see LICENSE.md or https://www.libelektra.org)

Function Documentation

opmphmPredictor()

int opmphmPredictor	(	OpmphmPredictor *	op,
		size_t	n
	)

Predictcs at the first ksLookup (...) after a KeySet changed if it will be worth using the OPMPHM.

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

)

Allocates and initializes the OpmphmPredictor.

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 above the OPMPHM usage is worth.

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 = 0x1FF

The benchmarked and evaluated values of the predictors configuration.

Order Preserving Minimal Perfect Hash Map Predictor.