gem5::compression::DictionaryCompressor< T >::DeltaPattern< DeltaSizeBits > Class Template Reference

A pattern that checks whether the difference of the value and the dictionary entries' is below a certain threshold. More...

#include <dictionary_compressor.hh>

Inheritance diagram for gem5::compression::DictionaryCompressor< T >::DeltaPattern< DeltaSizeBits >:

Public Member Functions
	DeltaPattern (const int number, const uint64_t code, const uint64_t metadata_length, const int match_location, const DictionaryEntry bytes)
DictionaryEntry	decompress (const DictionaryEntry dict_bytes) const override
	Decompress the pattern.
Public Member Functions inherited from gem5::compression::DictionaryCompressor< T >::Pattern
	Pattern (const int number, const uint64_t code, const uint64_t metadata_length, const uint64_t num_unmatched_bits, const int match_location, const bool allocate=true)
	Default constructor.
virtual	~Pattern ()=default
	Default destructor.
int	getPatternNumber () const
	Get enum number associated to this pattern.
uint8_t	getCode () const
	Get code of this pattern.
uint8_t	getMatchLocation () const
	Get the index of the dictionary match location.
virtual std::size_t	getSizeBits () const
	Get size, in bits, of the pattern (excluding prefix).
bool	shouldAllocate () const
	Determine if pattern allocates a dictionary entry.
std::string	print () const
	Extract pattern's information to a string.

Static Public Member Functions
static bool	isValidDelta (const DictionaryEntry &bytes, const DictionaryEntry &base_bytes)
	Compares a given value against a base to calculate their delta, and then determines whether it fits a limited sized container.
static bool	isPattern (const DictionaryEntry &bytes, const DictionaryEntry &dict_bytes, const int match_location)

Private Attributes
const DictionaryEntry	bytes
	The original value.

Additional Inherited Members
Protected Attributes inherited from gem5::compression::DictionaryCompressor< T >::Pattern
const int	patternNumber
	Pattern enum number.
const uint8_t	code
	Code associated to the pattern.
const uint8_t	length
	Length, in bits, of the code and match location.
const uint8_t	numUnmatchedBits
	Number of unmatched bits.
const int	matchLocation
	Index representing the the match location.
const bool	allocate
	Wether the pattern allocates a dictionary entry or not.

Detailed Description

template<class T>
template<std::size_t DeltaSizeBits>
class gem5::compression::DictionaryCompressor< T >::DeltaPattern< DeltaSizeBits >

A pattern that checks whether the difference of the value and the dictionary entries' is below a certain threshold.

If so, the pattern is successful, and only the delta bits need to be stored.

For example, if the delta can only contain up to 4 bits, and the dictionary contains the entry 0xA231, the value 0xA232 would be compressible, and the delta 0x1 would be stored. The value 0xA249, on the other hand, would not be compressible, since its delta (0x18) needs 5 bits to be stored.

Template Parameters

DeltaSizeBits

Size of a delta entry, in number of bits, which determines the threshold. Must always be smaller than the dictionary entry type's size.

Definition at line 682 of file dictionary_compressor.hh.

Constructor & Destructor Documentation

DeltaPattern()

template<class T >

template<std::size_t DeltaSizeBits>

gem5::compression::DictionaryCompressor< T >::DeltaPattern< DeltaSizeBits >::DeltaPattern ( const int number, const uint64_t code, const uint64_t metadata_length, const int match_location, const DictionaryEntry bytes )

inline

Definition at line 697 of file dictionary_compressor.hh.

Member Function Documentation

decompress()

template<class T >

template<std::size_t DeltaSizeBits>

DictionaryEntry gem5::compression::DictionaryCompressor< T >::DeltaPattern< DeltaSizeBits >::decompress ( const DictionaryEntry dict_bytes ) const

inlineoverridevirtual

Decompress the pattern.

Each pattern has its own way of interpreting its data.

Parameters

dict_bytes

The bytes in the corresponding matching entry.

Returns

The decompressed pattern.

Implements gem5::compression::DictionaryCompressor< T >::Pattern.

Definition at line 738 of file dictionary_compressor.hh.

isPattern()

template<class T >

template<std::size_t DeltaSizeBits>

static bool gem5::compression::DictionaryCompressor< T >::DeltaPattern< DeltaSizeBits >::isPattern ( const DictionaryEntry & bytes, const DictionaryEntry & dict_bytes, const int match_location )

inlinestatic

Definition at line 731 of file dictionary_compressor.hh.

isValidDelta()

template<class T >

template<std::size_t DeltaSizeBits>

static bool gem5::compression::DictionaryCompressor< T >::DeltaPattern< DeltaSizeBits >::isValidDelta ( const DictionaryEntry & bytes, const DictionaryEntry & base_bytes )

inlinestatic

Compares a given value against a base to calculate their delta, and then determines whether it fits a limited sized container.

Parameters

bytes	Value to be compared against base.
base_bytes	Base value.

Returns

Whether the value fits in the container.

Definition at line 717 of file dictionary_compressor.hh.

References gem5::X86ISA::base, gem5::compression::DictionaryCompressor< T >::fromDictionaryEntry(), gem5::X86ISA::limit, and gem5::ArmISA::mask.

Member Data Documentation

bytes

template<class T >

template<std::size_t DeltaSizeBits>

const DictionaryEntry gem5::compression::DictionaryCompressor< T >::DeltaPattern< DeltaSizeBits >::bytes

private

The original value.

In theory we should keep only the deltas, but the dictionary entry is not inserted in the dictionary before the call to the constructor, so the delta cannot be calculated then.

Definition at line 694 of file dictionary_compressor.hh.

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The documentation for this class was generated from the following file:

• mem/cache/compressors/dictionary_compressor.hh