# cm-post.R: compare solutions to the following post to
#            r-devel from carlos martinez 12 apr 2008:
# Looking for a simple, effective a minimum execution time solution.
# For a vector as:
# c(0,0,1,0,1,1,1,0,0,1,1,0,1,0,1,1,1,1,1,1)
# To transform it to the following vector without using any loops:
# c(0,0,1,0,1,2,3,0,0,1,2,0,1,0,1,2,3,4,5,6)

set.seed(1066) # for reproducibility
N <- 1e6
x <- as.double(runif(N) > .5)
x[1] <- 0      # seems to be needed for fhad (and fvin?)

fvin <- function(x) {
    ind <- which(x == 0)
    unlist(lapply(mapply(seq, ind, c(tail(ind, -1) - 1, length(x))),
                  function(y) cumsum(x[y])))
}
fdan <- function(x) {
     d <- diff(c(0,x,0))
     starts <- which(d == 1)
     ends <- which(d == -1)
     x[x == 1] <- unlist(lapply(ends - starts, function(n) 1:n))
     x
}
fdan2 <- function(x) {
    runs <- rle(x)
    runlengths <- runs$lengths[runs$values == 1]
    x[x == 1] <- unlist(lapply(runlengths, function(n) 1:n))
    x
}
fhad <- function(x)
    unlist(lapply(split(x, cumsum(x == 0)), seq_along)) - 1

# following requires "ra" for fast times www.milbo.users.sonic.net/ra
library(jit)
fjit <- function(x) { 
    jit(1)
    if (length(x) > 1)
        for (i in 2:length(x))
            if (x[i])
                x[i] <- x[i-1] + 1
    x
}
fgreg <- function(x)
   Reduce( function(x,y) x*y + y, x, accumulate=TRUE )

fanon <- function(x)
     x * unlist(lapply(rle(x)$lengths, seq))

cat("times with N =", N, "\n")
cat("dan",  system.time(ydan  <- fdan(x))[3],  "\n")
cat("dan2", system.time(ydan2 <- fdan2(x))[3], "\n")
cat("had",  system.time(yhad  <- fhad(x))[3],  "\n")
cat("vin",  system.time(yvin  <- fvin(x))[3],  "\n")
cat("jit",  system.time(yjit  <- fjit(x))[3],  "\n")
cat("greg", system.time(ygreg <- fgreg(x))[3], "\n")
# very slow cat("anon", system.time(yanon <- fanon(x))[3], "\n")

stopifnot(identical(ydan2, ydan))
stopifnot(identical(as.numeric(yhad), ydan))
stopifnot(identical(yvin, ydan))
stopifnot(identical(yjit, ydan))
stopifnot(identical(ygreg, ydan))
# stopifnot(identical(yanon, ydan))