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# File src/library/base/R/apply.R
# Part of the R package, http://www.R-project.org
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# A copy of the GNU General Public License is available at
# http://www.r-project.org/Licenses/
applyPar <- function(X, MARGIN, FUN, ...)
{
FUN <- match.fun(FUN)
## Ensure that X is an array object
d <- dim(X)
dl <- length(d)
if(dl == 0)
stop("dim(X) must have a positive length")
ds <- 1:dl
if(length(oldClass(X)) > 0)
X <- if(dl == 2) as.matrix(X) else as.array(X)
## now recompute things as coercion can change dims
## (e.g. when a data frame contains a matrix).
d <- dim(X)
dn <- dimnames(X)
## Extract the margins and associated dimnames
s.call <- ds[-MARGIN]
s.ans <- ds[MARGIN]
d.call <- d[-MARGIN]
d.ans <- d[MARGIN]
dn.call<- dn[-MARGIN]
dn.ans <- dn[MARGIN]
## dimnames(X) <- NULL
## do the calls
d2 <- prod(d.ans)
if(d2 == 0) {
## arrays with some 0 extents: return ``empty result'' trying
## to use proper mode and dimension:
## The following is still a bit `hackish': use non-empty X
newX <- array(vector(typeof(X), 1), dim = c(prod(d.call), 1))
ans <- FUN(if(length(d.call) < 2) newX[,1] else
array(newX[,1], d.call, dn.call), ...)
return(if(is.null(ans)) ans else if(length(d.ans) < 2) ans[1][-1]
else array(ans, d.ans, dn.ans))
}
## else
newX <- aperm(X, c(s.call, s.ans))
dim(newX) <- c(prod(d.call), d2)
#### ans <- vector("list", d2)
nw <- getDoParWorkers()
if(length(d.call) < 2) {# vector
if (length(dn.call)) dimnames(newX) <- c(dn.call, list(NULL))
#### for(i in 1:d2) {
#### tmp <- FUN(newX[,i], ...)
#### if(!is.null(tmp)) ans[[i]] <- tmp
#### }
ans <- foreach(x=iblkcol(newX, nw), .combine='c', .packages='foreach') %dopar% {
foreach(i=1:ncol(x)) %do% FUN(x[,i], ...)
}
} else {
#### for(i in 1:d2) {
#### tmp <- FUN(array(newX[,i], d.call, dn.call), ...)
#### if(!is.null(tmp)) ans[[i]] <- tmp
#### }
ans <- foreach(x=iblkcol(newX, nw), .combine='c', .packages='foreach') %dopar% {
foreach(y=1:ncol(x)) %do% FUN(array(x[,i], d.call, dn.call), ...)
}
}
## answer dims and dimnames
ans.list <- is.recursive(ans[[1]])
l.ans <- length(ans[[1]])
ans.names <- names(ans[[1]])
if(!ans.list)
ans.list <- any(unlist(lapply(ans, length)) != l.ans)
if(!ans.list && length(ans.names)) {
all.same <- sapply(ans, function(x) identical(names(x), ans.names))
if (!all(all.same)) ans.names <- NULL
}
len.a <- if(ans.list) d2 else length(ans <- unlist(ans, recursive = FALSE))
if(length(MARGIN) == 1 && len.a == d2) {
names(ans) <- if(length(dn.ans[[1]])) dn.ans[[1]] # else NULL
return(ans)
}
if(len.a == d2)
return(array(ans, d.ans, dn.ans))
if(len.a > 0 && len.a %% d2 == 0) {
if(is.null(dn.ans)) dn.ans <- vector(mode="list", length(d.ans))
dn.ans <- c(list(ans.names), dn.ans)
return(array(ans, c(len.a %/% d2, d.ans),
if(!all(sapply(dn.ans, is.null))) dn.ans))
}
return(ans)
}
##############################################################################
#
# Something like this will be added to the iterators package.
# This creates an iterator over block columns of a matrix.
iblkcol <- function(a, chunks) {
n <- ncol(a)
i <- 1
nextEl <- function() {
if (chunks <= 0 || n <= 0) stop('StopIteration')
m <- ceiling(n / chunks)
r <- seq(i, length=m)
i <<- i + m
n <<- n - m
chunks <<- chunks - 1
a[,r, drop=FALSE]
}
obj <- list(nextElem=nextEl)
class(obj) <- c('abstractiter', 'iter')
obj
}
# Simple test program for applyPar
library(foreach)
x <- matrix(rnorm(16000000), 4000)
actual <- applyPar(x, 2, mean)
expected <- apply(x, 2, mean)
cat(sprintf('Result correct: %s\n', identical(actual, expected)))
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