vmode

vmode.default

vmode.ff

vmode&lt;-

vmode&lt;-.default

vmode&lt;-.ff

.vmode

.vunsigned

.vvalues

.vimplemented

.rammode

.ffmode

.vmin

.vmax

.vNA

.rambytes

.ffbytes

.vcoerceable

regtest.vmode

value

The <code>&#8230;</code> don't have a function yet, they are only defined to keep the generic flexible.

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Function <code class="command">vmode</code> returns virtual storage modes of 'ram' or 'ff' objects, the generic <code class="command">vmode&lt;-</code> sets the vmode of ram objects (vmode of ff objects cannot be changed).

 attribute

 data

 IO 

The ff package provides data structures that are stored on
disk but behave (almost) as if they were in RAM by transparently
mapping only a section (pagesize) in main memory - the effective
virtual memory consumption per ff object. ff supports R's standard
atomic data types 'double', 'logical', 'raw' and 'integer' and
non-standard atomic types boolean (1 bit), quad (2 bit unsigned),
nibble (4 bit unsigned), byte (1 byte signed with NAs), ubyte (1 byte
unsigned), short (2 byte signed with NAs), ushort (2 byte unsigned),
single (4 byte float with NAs). For example 'quad' allows efficient
storage of genomic data as an 'A','T','G','C' factor. The unsigned
types support 'circular' arithmetic. There is also support for
close-to-atomic types 'factor', 'ordered', 'POSIXct', 'Date' and
custom close-to-atomic types.
ff not only has native C-support for vectors, matrices and arrays
with flexible dimorder (major column-order, major row-order and
generalizations for arrays). There is also a ffdf class not unlike
data.frames and import/export filters for csv files.
ff objects store raw data in binary flat files in native encoding,
and complement this with metadata stored in R as physical and virtual
attributes. ff objects have well-defined hybrid copying semantics,
which gives rise to certain performance improvements through
virtualization. ff objects can be stored and reopened across R
sessions. ff files can be shared by multiple ff R objects
(using different data en/de-coding schemes) in the same process
or from multiple R processes to exploit parallelism. A wide choice of
finalizer options allows to work with 'permanent' files as well as
creating/removing 'temporary' ff files completely transparent to the
user. On certain OS/Filesystem combinations, creating the ff files
works without notable delay thanks to using sparse file allocation.
Several access optimization techniques such as Hybrid Index
Preprocessing and Virtualization are implemented to achieve good
performance even with large datasets, for example virtual matrix
transpose without touching a single byte on disk. Further, to reduce
disk I/O, 'logicals' and non-standard data types get stored native and
compact on binary flat files i.e. logicals take up exactly 2 bits to
represent TRUE, FALSE and NA.
Beyond basic access functions, the ff package also provides
compatibility functions that facilitate writing code for ff and ram
objects and support for batch processing on ff objects (e.g. as.ram,
as.ff, ffapply). ff interfaces closely with functionality from package
'bit': chunked looping, fast bit operations and coercions between
different objects that can store subscript information ('bit',
'bitwhich', ff 'boolean', ri range index, hi hybrid index). This allows
to work interactively with selections of large datasets and quickly
modify selection criteria.
Further high-performance enhancements can be made available upon request.

Jens Oehlschl�gel

Memory-Efficient Storage of Large Data on Disk and Fast Access
Functions

vmode function

Function <code class='command'>vmode</code> returns virtual storage modes of 'ram' or 'ff' objects, the generic <code class='command'>vmode&lt;-</code> sets the vmode of ram objects (vmode of ff objects cannot be changed).

Virtual storage mode — vmode

Virtual storage mode

`.vmode`	virtual mode
`.vunsigned`	TRUE if unsigned vmode
`.vvalues`	number of possible values (incl. NA)
`.vimplemented`	TRUE if this vmode is available in ff (initialized `.onLoad` and stored in `globalenv` )
`.rammode`	storage mode of this vmode
`.ffmode`	integer used to code the vmode in C-code
`.vvalues`	number of possible integers incl. NA in this vmode (or NA for other vmodes)
`.vmin`	min integer in this vmode (or NA for other vmodes)
`.vmax`	max integer in this vmode (or NA for other vmodes)
`.vNA`	NA or 0 if no NA for this vmode
`.rambytes`	bytes needed in ram
`.ffbytes`	bytes needed by ff on disk
`.vcoerceable`	list of vectors with those vmodes that can absorb this vmode

`vector.vmode`	creating (ram) vector of some vmode
`as.vmode`	generic for coercing to some vmode (dropping other attributes)
`vmode<-`	generic for coercing to some vmode (keeping other attributes)
`maxffmode`	determine lowest `.ffmode` that can absorb all input vmodes without information loss

creation	coercion	vmode description
`boolean`	`as.boolean`	1 bit logical without NA
`logical`	`as.logical`	2 bit logical with NA
`quad`	`as.quad`	2 bit unsigned integer without NA
`nibble`	`as.nibble`	4 bit unsigned integer without NA
`byte`	`as.byte`	8 bit signed integer with NA
`ubyte`	`as.ubyte`	8 bit unsigned integer without NA
`short`	`as.short`	16 bit signed integer with NA
`ushort`	`as.ushort`	16 bit unsigned integer without NA
`integer`	`as.integer`	32 bit signed integer with NA
`single`	`as.single`	32 bit float
`double`	`as.double`	64 bit float
`complex`	`as.complex`	2x64 bit float
`raw`	`as.raw`	8 bit unsigned char
`character`	`as.character`	character

vmode: Virtual storage mode

Description

Usage

Arguments

Value

Details

See Also

Examples