[R] [R-sig-hpc] Quickest way to make a large "empty" file on disk?

[Denham Robert]

Jonathon,
        10,000 numbers is pretty small, so I don't think time will be a
big problem. You could write this using writeBin with no problems. For
larger files, why not just use a loop? The writing is pretty fast, so I
don't think you'll have too many problems. 

On my machine:

> ptm <- proc.time()
> zz <- file("testbin.bin", "wb")
> for(i in 100000) writeBin(rep(0,100000000),zz, size=16)
> close(zz)
> proc.time() - ptm
   user  system elapsed 
  2.416   1.728  16.705 
 
Otherwise I would suggest writing a little piece of c code to do what
you want.

Robert
  

-----Original Message-----
From: r-sig-hpc-bounces at r-project.org
[mailto:r-sig-hpc-bounces at r-project.org] On Behalf Of Jonathan Greenberg
Sent: Thursday, 3 May 2012 8:24 AM
To: r-help; r-sig-hpc at r-project.org
Subject: [R-sig-hpc] Quickest way to make a large "empty" file on disk?

R-helpers:

What would be the absolute fastest way to make a large "empty" file
(e.g.
filled with all zeroes) on disk, given a byte size and a given number
number of empty values.  I know I can use writeBin, but the "object" in
this case may be far too large to store in main memory.  I'm asking
because I'm going to use this file in conjunction with mmap to do
parallel writes to this file.  Say, I want to create a blank file of
10,000 floating point numbers.

Thanks!

--j

--
Jonathan A. Greenberg, PhD
Assistant Professor
Department of Geography and Geographic Information Science University of
Illinois at Urbana-Champaign
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