Elektra  0.8.25
Functions | Variables
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 <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.

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
opthe Predictor
nthe number of elements in the KeySet
Return values
1it is worth using the OPMPHM
0it is not worth using the OPMPHM

◆ opmphmPredictorCopy()

void opmphmPredictorCopy ( OpmphmPredictor *  dest,
OpmphmPredictor *  source 
)

Make a copy of the OpmphmPredictor.

Parameters
sourcethe OpmphmPredictor source
destthe OpmphmPredictor destination

◆ opmphmPredictorDel()

void opmphmPredictorDel ( OpmphmPredictor *  op)

Deletes the OpmphmPredictor.

Clears and frees all memory in OpmphmPredictor.

Parameters
opthe OpmphmPredictor

◆ opmphmPredictorIncCountBinarySearch()

int opmphmPredictorIncCountBinarySearch ( OpmphmPredictor *  op,
size_t  n 
)
inline

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

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

Parameters
opthe Predictor
nthe number of elements in the KeySet
Return values
1it is worth using the OPMPHM
0it is not worth using the OPMPHM

◆ opmphmPredictorIncCountOpmphm()

void opmphmPredictorIncCountOpmphm ( OpmphmPredictor *  op)
inline

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

Parameters
opthe 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
NULLmemory 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
nthe number of elements in the KeySet
Return values
size_tthe 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.