https://github.com/cran/multicore
Tip revision: 3d21cbc109aa07b0381edc505de0ce86c017a1ef authored by Simon Urbanek on 08 August 1977, 00:00:00 UTC
version 0.1-2
version 0.1-2
Tip revision: 3d21cbc
mclapply.R
mclapply <- function(X, FUN, ..., mc.preschedule=TRUE, mc.set.seed=TRUE, mc.silent=FALSE, mc.cores=getOption("cores")) {
env <- parent.frame()
cores <- mc.cores
if (is.null(cores)) cores <- volatile$detectedCores
cores <- as.integer(cores)
if (!mc.preschedule) { # sequential (non-scheduled)
FUN <- match.fun(FUN)
if (length(X) <= cores) { # all-out, we can use one-shot parallel
jobs <- lapply(seq(X), function(i) parallel(FUN(X[[i]], ...), name=names(X)[i], mc.set.seed=mc.set.seed, silent=mc.silent))
res <- collect(jobs)
if (length(res) == length(X)) names(res) <- names(X)
return(res)
} else { # more complicated, we have to wait for jobs selectively
sx <- seq(X)
res <- lapply(sx, function(x) NULL)
names(res) <- names(X)
ent <- rep(FALSE, length(X)) # values entered (scheduled)
fin <- rep(FALSE, length(X)) # values finished
jobid <- 1:cores
jobs <- lapply(jobid, function(i) parallel(FUN(X[[i]], ...), mc.set.seed=mc.set.seed, silent=mc.silent))
jobsp <- processID(jobs)
ent[jobid] <- TRUE
while (!all(fin)) {
s <- selectChildren(jobs, 0.5)
if (is.null(s)) break # no children -> no hope
if (is.integer(s)) for (ch in s) {
ji <- which(jobsp == ch)[1]
ci <- jobid[ji]
r <- readChild(ch)
if (is.raw(r)) res[[ci]] <- unserialize(r)
else {
fin[ci] <- TRUE
# cat("fin: "); print(fin)
# cat("res: "); print(unlist(lapply(res, is.null)))
if (!all(ent)) { # still something to do, spawn a new job
nexti <- which(!ent)[1]
jobid[ji] <- nexti
jobs[[ji]] <- parallel(FUN(X[[nexti]], ...), mc.set.seed=mc.set.seed, silent=mc.silent)
jobsp[ji] <- processID(jobs[[ji]])
ent[nexti] <- TRUE
}
}
}
}
return(res)
}
}
if (length(X) < cores) cores <- length(X)
if (cores < 2) return(lapply(X, FUN, ...))
sindex <- lapply(1:cores, function(i) seq(i,length(X), by=cores))
schedule <- lapply(1:cores, function(i) X[seq(i,length(X), by=cores)])
ch <- list()
res <- lapply(seq(X), function(x) NULL)
names(res) <- names(X)
cp <- rep(0L, cores)
fin <- rep(FALSE, cores)
dr <- rep(FALSE, cores)
inner.do <- function(core) {
S <- schedule[[core]]
f <- fork()
if (inherits(f, "masterProcess")) { # child process
on.exit(exit(1,structure("fatal error in wrapper code",class="try-error")))
if (isTRUE(mc.set.seed)) set.seed(Sys.getpid())
if (isTRUE(mc.silent)) closeStdout()
sendMaster(try(lapply(S, FUN, ...), silent=TRUE))
exit(0)
}
ch[[core]] <<- f
cp[core] <<- f$pid
NULL
}
lapply(1:cores, inner.do)
ac <- cp[cp > 0]
while (!all(fin)) {
s <- selectChildren(ac, 1)
if (is.null(s)) break # no children -> no hope we get anything
if (is.integer(s)) for (ch in s) {
a <- readChild(ch)
if (is.integer(a)) {
core <- which(cp == a)
fin[core] <- TRUE
} else if (is.raw(a)) {
core <- which(cp == attr(a, "pid"))
res[[core]] <- unserialize(a)
dr[core] <- TRUE
}
}
}
# str(res)
ores <- list()
for (i in 1:cores) ores[sindex[[i]]] <- res[[i]]
if (length(names(X)) == length(ores)) names(ores) <- names(X)
ores
}
#mcapply(1:4, function(i) i+1)