[R] List assignment in a while loop and timing

[Saptarshi Guha]

Hello R users
I have question about the time involved in list assignment.
Consider the following code snippet(see below). The first line creates
a reader object,
which is the interface to 1MM key-value pairs (serialized R objects) spanning 50
files (a total of 50MB). rhsqstart initiates the reading and I loop, reading
each key-value pair using rhsqnextKVR. If this returns NULL, we switch to the
next file and if this returns null we break.

If I comment out line A1, it takes 39 seconds on a quad core intel with
16GB ram running R-2.8
If I include the assignment A1 it takes ~85 seconds.

I have preassigned the list in line A0, so I'm guessing there is no resizing
going on, so why does the time increase so much?

Thank you for your time.
Regards
Saptarshi


==code==
rdr <- rhsqreader("~/tmp/pp",local=T,pattern="^p")
rdr <- rhsqstart(rdr)
i <- 1;
h=as.list(rep(1,1e6)) ##A0
while(TRUE){
  value <-rhsqnextKVR(rdr) ##Returns a list of two elements K,V
  if(is.null(value)) {
    message(rdr$df[rdr$current])
    rdr <- rhsqnextpath(rdr)
    if(is.null(rdr)) break;
  }
  h[[i]] <- value; ##A1
  i <- i+1
}