tatami_chunked::OracularSubsettedSlabCache< Id_, Index_, Slab_ > Class Template Reference

Oracle-aware cache for slabs, plus subsets. More...

#include <OracularSubsettedSlabCache.hpp>

Public Member Functions
	OracularSubsettedSlabCache (std::shared_ptr< const tatami::Oracle< Index_ > > oracle, size_t max_slabs)
	OracularSubsettedSlabCache (const OracularSubsettedSlabCache &)=delete
OracularSubsettedSlabCache &	operator= (const OracularSubsettedSlabCache &)=delete
Index_	next ()
template<class Ifunction_ , class Cfunction_ , class Pfunction_ >
std::pair< const Slab_ *, Index_ >	next (Ifunction_ identify, Cfunction_ create, Pfunction_ populate)
size_t	get_max_slabs () const
size_t	get_num_slabs () const

Detailed Description

template<typename Id_, typename Index_, class Slab_>
class tatami_chunked::OracularSubsettedSlabCache< Id_, Index_, Slab_ >

Oracle-aware cache for slabs, plus subsets.

Template Parameters

Id_	Type of slab identifier, typically integer.
Index_	Type of row/column index produced by the oracle.
Slab_	Class for a single slab.

Implement an oracle-aware cache for slab subsets. Each slab is defined as the set of chunks required to read an element of the target dimension (or a contiguous block/indexed subset thereof) from a tatami::Matrix. This cache is similar to the OracularSlabCache except that it remembers the subset of elements on the target dimension that were requested for each slab. Slab extractors can use this information to optimize slab loading by ignoring unneeded elements.

Constructor & Destructor Documentation

OracularSubsettedSlabCache() [1/2]

template<typename Id_ , typename Index_ , class Slab_ >

tatami_chunked::OracularSubsettedSlabCache< Id_, Index_, Slab_ >::OracularSubsettedSlabCache ( std::shared_ptr< const tatami::Oracle< Index_ > >  oracle, size_t  max_slabs  )

inline

Parameters

oracle	Pointer to an tatami::Oracle to be used for predictions.
max_slabs	Maximum number of slabs to store.

OracularSubsettedSlabCache() [2/2]

template<typename Id_ , typename Index_ , class Slab_ >

tatami_chunked::OracularSubsettedSlabCache< Id_, Index_, Slab_ >::OracularSubsettedSlabCache ( const OracularSubsettedSlabCache< Id_, Index_, Slab_ > &  )

delete

Deleted as the cache holds persistent pointers.

Member Function Documentation

operator=()

template<typename Id_ , typename Index_ , class Slab_ >

OracularSubsettedSlabCache & tatami_chunked::OracularSubsettedSlabCache< Id_, Index_, Slab_ >::operator= ( const OracularSubsettedSlabCache< Id_, Index_, Slab_ > &  )

delete

Deleted as the cache holds persistent pointers.

next() [1/2]

template<typename Id_ , typename Index_ , class Slab_ >

Index_ tatami_chunked::OracularSubsettedSlabCache< Id_, Index_, Slab_ >::next ( )

inline

This method is intended to be called when num_slabs = 0, to provide callers with the oracle predictions for non-cached extraction of data. Calls to this method should not be intermingled with calls to its overload below; the latter should only be called when max_slabs > 0.

Returns

The next prediction from the oracle.

next() [2/2]

template<typename Id_ , typename Index_ , class Slab_ >

template<class Ifunction_ , class Cfunction_ , class Pfunction_ >

std::pair< const Slab_ *, Index_ > tatami_chunked::OracularSubsettedSlabCache< Id_, Index_, Slab_ >::next ( Ifunction_  identify, Cfunction_  create, Pfunction_  populate  )

inline

Fetch the next slab according to the stream of predictions provided by the tatami::Oracle. This method should only be called if num_slabs > 0 in the constructor; otherwise, no slabs are actually available and cannot be returned.

Template Parameters

Ifunction_	Function to identify the slab containing each predicted row/column.
Cfunction_	Function to create a new slab.
Pfunction_	Function to populate zero, one or more slabs with their contents.

Parameters

identify	Function that accepts an i, an Index_ containing the predicted index of a single element on the target dimension. This should return a pair containing: An Id_, the identifier of the slab containing i. This is typically defined as the index of the slab on the target dimension. For example, if each chunk takes up 10 rows, attempting to access row 21 would require retrieval of slab 2. An Index_, the index of row/column i inside that slab. For example, if each chunk takes up 10 rows, attempting to access row 21 would yield an offset of 1.
create	Function that accepts no arguments and returns a Slab_ object with sufficient memory to hold a slab's contents when used in populate(). This may also return a default-constructed Slab_ object if the allocation is done dynamically per slab in populate().
populate	Function that accepts a std::vector<std::tuple<Id_, Slab_*, const OracularSubsettedSlabCacheSelectionDetails<Index_>*> >& specifying the slabs to be populated. The first Id_ element of each tuple contains the slab identifier, i.e., the first element returned by the identify function. The second Slab_* element specifies the object which to store the contents of the slab. The third OracularSubsettedSlabCacheSelectionDetails<Index_>* element contains information about the desired subset of elements on the target dimension of the slab. This function should iterate over the vector and populate the desired subset of each slab. The vector is guaranteed to be non-empty but is not guaranteed to be sorted.

Returns

Pair containing (1) a pointer to a cached slab and (2) the index of the next predicted row/column inside the retrieved slab.

get_max_slabs()

template<typename Id_ , typename Index_ , class Slab_ >

size_t tatami_chunked::OracularSubsettedSlabCache< Id_, Index_, Slab_ >::get_max_slabs ( ) const

inline

Returns

Maximum number of slabs in the cache.

get_num_slabs()

template<typename Id_ , typename Index_ , class Slab_ >

size_t tatami_chunked::OracularSubsettedSlabCache< Id_, Index_, Slab_ >::get_num_slabs ( ) const

inline

Returns

Number of slabs currently in the cache.

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

• tatami_chunked/OracularSubsettedSlabCache.hpp