describe, attach.big.matrix {bigmemory} | R Documentation |
The attach.big.matrix
creates a new big.matrix
object which
references previously allocated shared memory or file-backed matrices.
The describe
function returns the description needed by the
attach.big.matrix
function so that a newly created big.matrix
instance can reference a previously allocated shared memory instance of
type big.matrix
.
describe(x) attach.big.matrix(obj, backingpath='')
x |
a shared big.matrix . |
obj |
an object as returned by describe() or, optionally, the filename of the descriptor for a filebacked matrix, assumed to be in the directory specified by the backingpath (if one is provided). |
backingpath |
the path where the descriptor and/or filebacking can be found. |
After a shared (possible file-backed)
big.matrix
instance is created, the describe
function
can be called to retrieve the keys which refer to the shared memory locations
which the instance manages. These keys are then used for a new shared
big.matrix
instance to refer to the same memory across R sessions.
A descriptor file is automatically created when a new filebacked big.matrix
is created, so in this case, the describe()
is unnecessary (but may still
be helpful).
describe
returns a list of shared memory keys and other necessary information.
attach.big.matrix
return a new instance of type big.matrix
which
refers to the shared memory described by the describe
function.
John W. Emerson and Michael J. Kane
bigmemory
, big.matrix
, or the class documentation big.matrix
.
# The example is quite silly, as you wouldn't likely do this in a # single R session. But if zdescription were passed to another R session # via SNOW, NetWorkSpaces, or even by a simple file read/write, # then the attach of the second R process would give access to the # same object in memory. Please see the package vignette for real examples. z <- shared.big.matrix(3, 3, type='integer', init=3) z[,] dim(z) z[1,1] <- 2 z[,] zdescription <- describe(z) zdescription y <- attach.big.matrix(zdescription) y[,] y z y[1,1] <- -100 y[,] z[,]