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hi

Hybrid index class

Description

Class for hybrid index representation, plain and rle-packed

Usage

hi(from, to, by = 1L, maxindex = NA, vw = NULL, pack = TRUE, NAs = NULL)
## S3 method for class 'hi'
print(x, ...)
## S3 method for class 'hi'
str(object, nest.lev=0, ...)

Arguments

`from`	integer vector of lower sequence bounds
`to`	integer vector of upper sequence bounds
`by`	integer of stepsizes
`maxindex`	maximum indep position (needed for negative indices)
`vw`	virtual window information, see `vw`
`pack`	FALSE to suppress rle-packing
`NAs`	a vector of NA positions (not yet used)
`x`	an object of class 'hi' to be printed
`object`	an object of class 'hi' to be str'ed
`nest.lev`	current nesting level in the recursive calls to str
`...`	further arguments passed to the next method

Details

Class hi will represent index data either as a plain positive or negative index vector or as an rle-packed version thereof. The current implementation switches from plain index positions i to rle-packed storage of diff(i) as soon as the compression ratio is 3 or higher. Note that sequences shorter than 2 must never be packed (could cause C-side crash). Furthermore hybrid indices are guaranteed to be sorted ascending, which helps ffs access method avoiding to swap repeatedly over the same memory pages (or file positions).

Value

A list of class 'hi' with components

`x`	directly accessed by the C-code: the sorted index of class 'rlepack' as returned by `rlepack`
`ix`	NULL or positions to restore original order
`re`	logical scalar indicating if sequence was reversed from descending to ascending (in this case `is.null(ix)`)
`minindex`	directly accessed by the C-code: represents the lowest positive subscript to be enumerated in case of negative subscripts
`maxindex`	directly accessed by the C-code: represents the highest positive subscript to be enumerated in case of negative subscripts
`length`	number of subscripts, whether negative or positive, not the number of selected elements
`dim`	NULL or dim – used by `as.matrix.hi`
`dimorder`	NULL or `dimorder`
`symmetric`	logical scalar indicating whether we have a symmetric matrix
`fixdiag`	logical scalar indicating whether we have a fixed diagonal (can only be true for symmetric matrices)
`vw`	virtual window information `vw`
`NAs`	NULL or NA positions as returned by `rlepack`

Note

hi defines the class structure, however usually as.hi is used to acturally Hybrid Index Preprocessing for ff

Author(s)

Jens Oehlschlägel

Examples

hi(c(1, 11, 29), c(9, 19, 21), c(1,1,-2))
  as.integer(hi(c(1, 11, 29), c(9, 19, 21), c(1,1,-2)))

ff

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

v4.0.4

GPL-2 | GPL-3 | file LICENSE

Authors

Daniel Adler [aut], Christian Gläser [aut], Oleg Nenadic [aut], Jens Oehlschlägel [aut, cre], Martijn Schuemie [aut], Walter Zucchini [aut]

Initial release

2020-10-13

hi